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Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan (1999)

Chapter: 5 Options for the Future: Balancing Water Demand and Water Resources

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Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

5
Options for the Future: Balancing Water Demand and Water Resources

The conventional freshwater sources now available in the region are barely sufficient to maintain the study area's current quality of life and economy. Jordan, for example, is currently overexploiting its groundwater resources by about 300 million cubic meters per year (million m3/yr), lowering water levels and salinizing freshwater aquifers; similar examples of overexploitation are occurring throughout the study area. Attempting to meet future regional demands by simply increasing withdrawals of surface and ground water will result in further unsustainable development, with depletion of freshwater resources and widespread environmental degradation. Because these conditions already exist in many parts of the study area, for example in the Azraq Basin and the Hula Valley, as described in Chapter 4, the reality of a constrained water supply must be considered in formulating government economic plans and policies. It seems likely that demand and supply can be brought into a sustainable balance only by changing and moderating the pattern of demand, or by introducing new sources of supply, or both. Above all, water losses should be minimized and water use efficiency increased substantially.

Managing Demand

Water shortages have already been faced in the study area as a result of droughts, and they have been overcome by managing demand. The reduction in Israeli water use from 1,987 million m3/yr in 1987 to 1,420

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

million m3/yr in 1991—with no net loss in agricultural production or economic growth (Biswas et al., 1997)—indicates what can be accomplished in the way of demand moderation. In practice, demand for water can be influenced by conservation measures in urban, agricultural, and industrial sectors, and by economic (pricing) policies. It is important to recognize that, while demand management efforts may economize on water effectively, they are also rarely costless. In this section, a number of demand-management policies are described and discussed in light of the committee's five evaluation criteria (see Chapter 3 for a full statement of the criteria).

Conservation

Given the inevitability of population growth, it is imperative that per capita consumption of water in the study area be addressed through conservation measures in all three major sectors of water use: urban, agricultural, and industrial. There are significant disparities in per capita water use within the study area, and there will doubtless be pressures to raise the lowest consumption rates to parity with the highest rates. However, some middle ground must be reached to bring quality of life and economic development into balance within the practical constraints imposed by the region's available water. This balance requires lowering the study area's capita water use without significantly degrading the economy or standard of living, and at the same time improving the economy, hygienic conditions, and standard of living among Jordanians and Palestinians.

Conservation measures to reduce water demand are generally well established, but they often require societal or economic incentives to implement. Although some conservation measures are costly, most compare favorably with measures to increase water supplies. Moreover, water conservation measures invariably have a positive effect on water quality and the environment, if only by minimizing the impacts on freshwater resources and the volumes of wastewater generated by human activities.

Urban

In urban and rural-domestic sectors elsewhere, notably the United States, conservation measures are most effective when they have broad public support. Important voluntary domestic water conservation measures include the following:

  • Limiting toilet flushing.
  • Adopting water-saving plumbing fixtures, such as toilets and shower heads.
Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×
  • Adopting water-efficient appliances (notably washing machines).
  • Limiting outdoor uses of water, as by watering lawns and gardens during the evening and early morning, and washing cars on lawns and without using a hose.
  • Adopting water-saving practices in commerce, such as providing water on request only in restaurants and encouraging multiday use of towels and linens in hotels.
  • Repairing household leaks.
  • Limiting use of garbage disposal units.

Public support of such measures is highly variable because many of them are voluntary, relying on individual actions, or have negative societal impacts (such as higher prices or taxes, as discussed below). The study area is at an advantage in this regard, because the population is relatively well aware of how water is used. Public awareness of levels of water use is the key to effective urban conservation programs.

Voluntary domestic conservation measures can result in significant water savings. Among such conservation measures, low-flush toilets use approximately 6 liters of water per flush, while conventional toilets operate with 13 to 19 liters. Toilet water-displacement devices, such as a simple water-filled plastic container, are placed in the toilet tank to reduce the amount of water used per flush. A toilet dam, one type of water-displacement device, saves 3.7 to 7.5 liters per flush. Low-flow shower heads are relatively inexpensive and save 7.5 liters per minute (U.S. EPA, 1995). Installing pressure-reducing valves can also save energy as well as water by reducing the probability of system leakage and breakdowns. The U.S. Environmental Protection Agency (U.S. EPA, 1995) estimated water savings for a house with low pressure, compared to a house with high pressure, to be 6 percent. Pressure reduction increases the reliability of water systems by 33 percent (Al-Weshah and Shaw, 1994).

According to Bargur (1993), the Israeli Water Commission has estimated that municipal water use in Israel could be reduced by 55 million m3/yr if voluntary conservation measures were widely implemented. Table 5.1 summarizes the household water savings that can be achieved using water-saving appliances. Because of the possibly significant cost savings of these voluntary conservation measures, their widespread adoption should be encouraged in the study area. As an example of the potential savings, a typical family of five persons that does not employ water conservation measures uses about 42 m3 of water per month, at a cost of US$42 (assuming an exchange rate of US$1 = 3.6 New Israeli Shekels [NIS] as of March 1998). With the full use of water-saving devices, monthly use for five people would likely be between 16 and 19.5 m3, a

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.1 Comparison of Conventional and Nonconventional Appliances in Domestic Water Use

Item

Conventional (1/unit)

Improved (1/unit)

Use Frequency (times/time/steps)

Savings with Improved Technology (m3/unit)

Savings/Month (m3)

Values (US$)

Toilet Flush

16 1/flush

Low-flow (6 1/flush)

5/person/day

0.050/day

1.5

1.5

 

 

Displacement device 8.7-12.3 1/flush

 

0.020/day

0.60

0.60

Shower Head

18.7-30 1/min at full capacity

Pressurized low-flow 7.5 1/min

1/person/day (10 min)

0.112-0.337/10 min

3.38-6.75

3.38-6.75

Bath

94-131 1/day

 

 

 

 

 

Tap

12-19 1/min at full capacity

 

 

 

 

 

Washing Machine

Full automatic, 131-263 1/wash

Manual 40-60 1/wash

3 cycles/wash

0.273-0.609/wash

0.588

0.588

Car Wash

Normal hoses for 20 minutes, 375 1

Pressurized hose for 20 minutes, 56 1

3/month

0.319/wash

0.96

0.96

 

SOURCE: U.S. EPA, 1995.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

reduction of as much as 62 percent. This amount could be a highly significant savings, especially for low-income families in the study area.

Involuntary conservation measures applied to the urban sector are easier but more expensive to implement. Such measures include repairing leaking distribution systems and sewer pipes, expanding central sewage systems, metering all water connections, and rationing and water use restrictions. Improvements to municipal water systems, such as repairing or replacing leaking distribution systems, and achieving total metering of all water use could be accomplished as part of government policy. An aggressive conservation policy, such as the one adopted in the Mexico City Metropolitan District, can extend to the elimination of household leaks as well as to the repair of leaks in the water distribution network (NRC, 1995). These measures are expensive, but the costs and potential water savings must be weighed against the costs of developing equivalent alternate supplies. The dynamic growth possible in both public and private sectors throughout the study area holds the promise of incorporating water conservation measures into the new infrastructures to be built.

Although per capita domestic water use in Israel has been increasing, from 80 cubic meters per year (m3/yr) in 1965 to 100 m3/yr in 1995, the disparity among localities in per capita use suggests that water use can be reduced without degrading the quality of life. While in Jerusalem the average per capita water use is 67 m3/yr, it is 117 in Tel Aviv, and 89 in Haifa (not including conveyance losses). In the low-income municipalities, water use rates are as low as 40 m 3/yr (Tahal, 1993). On the other hand, the domestic per capita use in rural areas in Israel is 196 m3/yr. The disparity in per capita use needs to be further investigated, insofar as it suggests that, under conditions of further constraint, there is still room for water conservation in the urban sector. Per capita water use for urban Palestinians reaches a maximum of 100 m3/yr, similar to Israeli use, and can reach 200 m3/yr, whereas in rural areas it is about 20 m3/yr, reflecting the widespread unavailability of water distribution networks as well as restricted water availability in these areas. Although Palestinian urban use may be lowered through conservation, rural use is likely to increase as water distribution systems become more widespread with improvements in the level of living. This development of new and larger water distribution facilities will increase the rate of water use unless restrictions are put in place first.

As a further indication of potential water savings, municipal authorities in the West Bank report that water losses unaccounted for in the distribution network range from 26 percent in Ramallah to 55 percent in Hebron (Hebron Municipal Water Engineer, personal interview, 1996). In Jordan, average water loss is 50 percent (Water Authority of Jordan open

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

files, 1996). The average 1990 water loss in the 40 largest municipalities in Israel was 11.3 percent (Tahal, 1993). Commonly, much of the apparent conveyance loss in municipal water systems is actually the result of illegal or nonmetered connections, or errors in metering. Accurate metering at all connections will promote the adoption of voluntary conservation measures as well as quantifying actual conveyance losses. Water leaking from freshwater distribution pipes may not be entirely wasted, because it may infiltrate and recharge ground water. On the other hand, water leaking from sewers and effluent from cesspools and other untreated waste-disposal systems pollute underlying ground water. Minimizing these sources would result in increased flows to wastewater treatment plants, which in turn would increase the amount of water available for reuse (see ''Wastewater Reclamation" below).

The quantity of additional water that can be made available for reuse by reducing losses from sewers may be significant. For example, the official figure describing the total quantity of wastewater in Israel (Table 5.2) is 374 million m3/yr. However, urban water use is 546 million m3/yr and industrial use is about 130 million m3/yr. About 10 to 20 percent of urban water goes to nonreturnable, consumptive uses (mostly irrigation of private and public gardens) and as much as 50 percent of industrial use is consumed. According to these assumptions, the potential amount of returned sewage from urban use in Israel is 437 million m3/yr (assuming a consumption rate of 20 percent), and the total amount of wastewater, including industrial wastewater, should be about 500 million m3/yr. The difference of about 125 million m3/yr between potential and actual wastewater represents the amount of water that can be made available through reuse of wastewater if sewering were total and losses minimized.

TABLE 5.2 Collection, Treatment, and Utilization of Wastewater Effluent in Israel, 1994

District

Population

Total Wastewater

Sewered

Treated

Utilized

Jerusalem

643,267

35,412

34,596

1,957

25,994

Northern

933,448

63,828

55,312

42,461

30,068

Haifa

716,460

52,184

49,120

43,900

36,431

Central

1,170,824

78,827

72,487

70,250

29,177

Tel Aviv

1,140,523

76,747

76,628

76,628

94,884

Southern

701,330

67,262

62,628

62,372

35,974

Total

5,305,852

374,303

350,771

297,570

252,529

NOTE: All values except population are million m3/yr.

SOURCE: Eitan, 1995.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

There are several possible explanations for this high deviation between the amount of water entering the city (urban water use) and that leaving (wastewater). Again, many municipal water-distribution systems leak. An additional and significant loss of water occurs in the wastewater disposal system. In small and medium-sized communities, many homes are not connected to sewers and dispose of their wastewater into septic tanks. The amount of sewage disposed of in septic tanks in Israel, which has the most extensive sewage collection system in the study area, was estimated to be about 50 million m3/yr. Beyond the fact that this water is not available for reuse as treated wastewater, septic tank effluent is a major cause of ground-water pollution. Another cause of water loss is the leakage of wastewater from sewers. Presently, municipalities do not have an incentive to fix leaks in sewers or to enforce closure of septic tanks. Often, the tacit interest of the municipality may be to minimize the amount of water reaching the wastewater treatment plant, to save water treatment expenses. Structural changes and improved maintenances of water distribution, and particularly wastewater distribution systems, may appear to be costly, but may be cost-effective compared to other measures that can produce comparable quantities of water.

In conclusion, Table 5.3 shows that urban water conservation efforts are attractive when evaluated against the five criteria established by the committee. Although conservation will not usually result in augmentation of available supplies—one possible exception being the repair of leaky distribution systems—conservation measures are generally technically and economically feasible; have no adverse environmental consequences; and, by conserving current water supplies, tend to preserve the resources available for both present and future generations.

TABLE 5.3 Demand Management

Committee Criterion

Conservation

 

 

Urban

Agriculture

Industry

Pricing

1.

Impact on Available Water Supply

0

0

0

0

2.

Technically Feasible

+

+

+

+

3.

Environmental Impact

0

+/-

+/0

+/-

4.

Economically Feasible

+

+/-

+/-

+/-

5.

Implications for Intergenerational Equity

+

+/0

+

+

NOTE: + indicates positive effects, - indicates negative effects, and 0 indicates no impact.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×
Agriculture

Water use in the agricultural sector throughout the study area is highly controlled by government agencies, and conservation measures have proven to be highly effective in reducing agricultural water use. The reduction in Israeli water use of more than 200 million m3/yr between 1985 and 1993 was accomplished almost entirely in the agricultural sector through the use of improved irrigation methods and water delivery restrictions. Agricultural water use may become even more efficient through rationing, research, and possibly economic policy involving changes in crops. However, as regional nonagricultural water demand increases and the cost of additional water supplies becomes more expensive, the role of agriculture in the area's economy will have to be reevaluated, to conserve as much water as possible. One possibility is that the area adopt agricultural practices more in harmony with the ecological realities of drylands. Drylands are and will probably always remain marginal for subsistence agriculture, unless it is heavily subsidized by water drawn from elsewhere. The alternative for sustainability is to develop local water resources and use them prudently, and at the same time to capitalize on local conditions and local resources in producing marketable products for export. Capturing local runoff and flood water can increase water supplies for dryland extensive agriculture (Evenari et al., 1982), and reducing evaporative water loss by cropping intensively within closed environments (using "desert greenhouses") can also effectively increase supplies. The latter practice requires financial investment and innovative technologies, but it is an economical use of land and water, it avoids salinization, and it produces a high yield of exportable cash crops such as out-of-season ornamentals, fruits, vegetables, and herbal plants.

Using computer-controlled drip "fertigation" (applying fertilizer with the irrigation water) economizes on water and fertilizer use, and prevents soil salinization and ground-water pollution. Use of brackish water, often abundant in the study area's dryland aquifers, for irrigating salinity-tolerant crops increases the sugar contents of fruits such as tomatoes and melons, and hence their market price. Brackish water is very useful for intensive aquaculture in deserts. Finally, the use of treated local or transported wastewater in subsurface drip irrigation of orchards and forage could dramatically increase the production of the study area's drylands in a sustainable manner. In any reevaluation of the role of agriculture in the study area, the socioeconomic impacts as well as the environmental impacts of changing agricultural practices should be considered.

In Jordan, 1996 agricultural water use per hectare was approximately 6,800 m3/yr. To increase the efficiency of water use, the Jordan Valley Authority has recently converted irrigation systems to pressure pipe networks.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

FIGURE 5.1 Average agricultural water use per hectare in Israel, 1950 to 1990. SOURCE: Stanhill, 1992.

In the West Bank and Gaza Strip, 1996 agricultural water use was about 7,150 m3/yr per hectare, much of it in drip irrigation and greenhouse agriculture. In Israel, where drip irrigation is widely practiced, the 1995 average agricultural water use per hectare was 5,700 m3/yr, down from 8,600 m3/yr in 1955 (see Figure 5.1) while crop productivity per unit of water (see Figure 5.2) increased more than twofold, from 1.2 to 2.5 kilograms per cubic meter (kg/m3) (Stanhill, 1992).

Experience in Israel has demonstrated how water-use efficiency can be increased by improvements in irrigation efficiency, increased crop productivity, and changes in the types of crops grown. Freshwater can also be saved by switching to irrigation with treated wastewater or brackish water (discussed further below). However, in Jordan the quality of wastewater effluent for irrigation may not be as high as in Israel (Salameh and Bannayan, 1993).

At present, over 80 percent of the irrigated area in Israel uses micro-irrigation techniques (drip and mini-sprinkler), with an irrigation efficiency of 85 to 90 percent. The remaining irrigated area uses sprinklers with an irrigation efficiency of 75 to 80 percent. Gravity irrigation, which has an efficiency of 50 to 60 percent, has not been used in Israel since the mid-1960s. Automation in irrigation has resulted in better water control

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

FIGURE 5.2 Irrigated crop productivity in Israel from 1950 to 1990.

SOURCE: Stanhill, 1992.

and the ability to irrigate at will (to avoid windy periods, for example), thereby reducing water losses (Box 5.1).

Determining crop water requirements for different areas in Israel was a high priority of agricultural research in the 1960s and 1970s. Table 5.4 presents results of scores of experiments throughout the country for some major crops (Shalhevet et al., 1981). The Israeli government (Water Commissioner) used the results of these experiments to set water allocations for growers in the various areas.

Another way of saving water in agriculture is by shifting production from crops with high water needs to crops with lower ones. This process occurred in Israel during the early years of crop irrigation and was partly responsible for reducing average per hectare water use over the past four decades, as illustrated in Figure 5.1. There is a limit to how much this approach can contribute to water savings, however, because water quality already limits the kinds of crops that can be profitably grown in the study area.

In designing agricultural water-conservation programs, care must be taken to ensure that the water conserved is not deep percolation water that would otherwise recharge an aquifer or runoff water that supplies another person or activity. Agricultural water conservation results in a net saving of water only when the water saved would otherwise be lost

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

BOX 5.1 Improved Water Use Efficiency in Traditional Farming in the Jiftlik Valley1

Background

The Jiftlik Valley is situated in the West Bank, east of Nablus. The valley leads from the city of Nablus to the Jordan Rift Valley. Before the early 1970s, the main crops grown were winter vegetables using traditional methods, by about 4,000 tenant farmers living in six villages, with an average annual per capita income lower than U.S.$200. The landlords provided the land, water-distribution system, water-use rights, access to credit, and marketing facilities. The farmers provided labor, traditional inputs like manure, and storage and packing facilities. The farm income was split half and half. During the winter growing season, the labor requirements were high, putting a strict limit on the land area each family could cultivate. No farming was carried out during the hot summer months.

The source of irrigation water was a number of springs flowing out of the highlands to the west. The water entered earthen ditches and was led through concrete-lined canals to the fields, where it was spread by gravity methods. Average irrigation efficiency was lower than 30 percent. Water was allocated on a time basis, on a 5-to 8-day cycle, and was used by one to four consumers at a time. There were no storage facilities, since under the traditional farming and irrigation system none were needed.

The Change from Traditional to Modern Farming

Modern irrigation farming is capital-intensive, requiring expensive inputs. Thus, the first requirement is a source of capital investment. For Jiftlik, the initial investment was made possible by a loan from the Mennonite Church. Further development was made possible based on income from farm activities. In other situations, government or banks may provide the initial credit.

The change from traditional to modern farming included a package of five inputs:

  1. Small farm ponds of 1,000 to 5,000 m3 each were constructed to make water supply more dependable.
  2. The traditional gravity irrigation method was replaced by drip irrigation, including peripheral equipment such as plastic supply lines, fittings, and values.
  3. Traditional crop varieties were replaced by seeds and seedlings of improved varieties, usually hybrids.

through consumptive use or severe degradation in quality. As shown in Table 5.3, agricultural water conservation will not usually increase available water. The water available does not increase because the conserved water has already been reused and allocated elsewhere. The environmental impact of agricultural water conservation also varies, with adverse impacts occurring where existing irrigation tailwaters or return flows support some environmental purpose. To the extent that agricultural

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×
  1. Plastic sheeting was used for mulching along the seedbed, construction of low tunnels during the cold season, and solar sterilization.
  2. Chemical fertilizer (a compound 20:20:20 mix) was introduced, simplifying fertilizer application, along with insecticides, fungicides, and herbicides.
  3. The farmers adopting these technologies were low income, partly illiterate, and dependent on their landlords. The landlord-tenant relationship has not been altered during the adoption of the new technologies and the lifestyle of the adult population has remained unchanged. The younger generation, however, has reaped the benefits of the improved affluence by having better health, training, and education.

    The adoption of advanced technologies has led to a notable change in farming patterns. Nonirrigated crops were completely abandoned in favor of intensive vegetable cropping, fewer types of crops were grown (6 vegetable crops instead of the 23 previously grown), and land use increased by over 60 percent. It became possible to grow two crops per year, for example, fall cucumbers and winter tomatoes, or fall tomatoes and spring watermelons and melons.

    From 1970 to 1986, the use of purchased inputs increased dramatically. An eightfold increase was seen in the number of tractors used and a sevenfold increase in the use of plastics, fertilizer, and seeds. The same amount of water irrigated nearly 10 times more land area than before the development process, and the irrigation method was changed from gravity irrigation (90 percent of the area in 1970) to drip irrigation (90 percent of a larger area in 1980). Yields increased three- to fivefold during the period 1965 to 1982. Equally important was the improvement in yield quality. The produce was now acceptable to the discriminating markets of the Arab oil states and Europe. Income per person increased from US$116 in 1966 to US$660 in 1974, to a peak of US$1,000 in 1980. In the late 1980s, income declined because of worsening market conditions, regional wars, and limitations imposed on imports by Jordan.

    This case study demonstrates that appropriate methods and proper investments can dramatically improve the traditional inefficient irrigation methods in the Middle East region, stretching the use of available water resources, while improving the income of the farmers. At the same time, labor requirements were not lowered. On the contrary, the greater yields required more labor for harvesting, sorting, and packing, although irrigation required less labor.

    1  

    Adapted from Rymon and Or, 1991.

water conservation results in net savings of water, it will tend to preserve water resources now and for future generations.

Industry

Water use in the industrial and commercial sector accounts for a relatively small percentage of total water use in the study area, ranging from 3 percent in the West Bank to 6 percent in Israel (Table 2.3). These figures,

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.4 Irrigation Requirements of Major Crops in Various Parts of Israel

Crop

Study Area

Irrigation Requirements (mm/year)

Expected Yield (kg/ha)

Wheat

Northern Negev

400-450

5,400

 

Beit Shean Valley

500-550

5,000

Sorghum

Coastal Plain

250-280

9,900

 

Northern Negev

380-420

7,800

Corn (grain)

Coastal Plain

330-350

8,500

 

Northern Negev

450-480

6,800

Cotton (lint)

Coastal Plain

330-360

1,760

 

Northern Negev

510-540

1,650

 

Bet Shean Valley

780-810

1,700

Peanuts

Coastal Plain

530-560

5,100

 

Northern Negev

530-560

4,600

Tomato (processing)

Coastal Plain

220-240

55,000

 

Northern Negev

410-430

64,700

 

SOURCE: Shalhevet et al., 1981.

however, do not take into account the many small factories and varied commercial establishments that are supplied by municipal water systems. For these smaller users, conservation measures adopted from the domestic sector, particularly through raising public awareness and adopting water-saving technologies, can result in significant overall water savings.

Most of the larger industrial users of water are self-supplied and many, particularly in Jordan, are largely unregulated (Salameh and Bannayan, 1993). Government-imposed water-use restrictions and pricing policies, together with wastewater quality requirements and impact fees, should motivate industrial and commercial users to reduce their water use. In Jordan, the steel and paper industries are recycling their cooling water with significant water savings. Daily water demand in a steel mill was reduced from 450 m3 to 20 m3 per day, and in a cardboard plant from 4,000 to 800 m3 per day (Water Authority of Jordan, written communication, 1994). In Israel, experience has shown that water recycling and the growth of industries that use very little water (for example, electronics) resulted in a decline in specific water use—that is, use of water per unit value of product. Further reductions in industrial freshwater use are possible in the study area through widespread reliance on

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

recycling systems, the development of new water-saving technologies, the use of lower quality water, and water use monitoring.

The evaluation of industrial water conservation and pricing policies based on the committee's five criteria is summarized in Table 5.3. Industrial conservation generally does not have an effect on the quantity of available water supply because most conservation schemes involve recycling within specific industrial plants. The environmental impact of industrial water conservation can be positive when wastewater flows to the ambient environment are reduced or eliminated through increased recycling. The economic feasibility of industrial water conservation varies from industry to industry and situation to situation. Where stringent wastewater discharge regulations require that water must be treated anyway, the incremental costs of recycling the water or making it suitable for nonpotable uses may be quite attractive. Finally, industrial recycling will tend to have positive implications now and for future generations because it economizes on water use and constrains—often significantly—degradation of water quality.

Prices and Pricing Policies

Water is typically priced to serve several different and sometimes conflicting objectives. First, the purveyor has the need to cover the costs of operating and maintaining the water delivery system and the debt service on it. Second, prices can be set to ensure that water is allocated and used efficiently, so that the total costs of meeting an area's water needs are minimized and consumers economize in using scarce resources. Third, water pricing almost always involves considerations of fairness. These considerations are usually taken to mean that equals should be charged equally and water rates should be perceived as fair by water consumers. Since these objectives frequently conflict, compromises must be made among them. Depending on the circumstances, one of these objectives may be relatively more important, and pricing policies will emphasize the important objective at the expense of the others (Boland, 1993).

In most regions of the world, strategies for developing and managing water resources have focused on the provision of water supplies. The emphasis on developing and augmenting water supplies generally leads to water pricing policies that emphasize achieving revenues sufficient to cover the costs of this development. In Israel, pricing policies have frequently been established to make water readily available. Some pricing policies have been designed to induce settlement of remote lands. These policies result in prices that understate the true cost of the water, signal consumers that water is more plentiful than it really is, and require subsidies

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

to recover costs. Similarly, pricing policies in many parts of the region emphasize affordability by setting prices low enough so that water bills remain relatively low. Water policies in the area have rarely been designed as part of an overall demand-management program and rarely result in prices that reflect the true value of the water.

It is instructive to examine policies based on the need to defray the cost of supply to illustrate how such policies may distort allocation patterns and levels of use in areas of increasing water scarcity. Water impoundment and conveyance facilities are almost always capital-intensive. This means that fixed costs are usually large compared to operating or variable costs. To ensure that the relatively large component of fixed costs is covered, pricing structures generally embody average cost-pricing rules so that the unit price becomes lower as use increases. Such rate structures tend to encourage use and discourage water economizing or conservation.

Pricing policies that emphasize economic efficiency and promote economizing in water use may be appropriate for the study area given its increasing water scarcity. Such policies will be particularly attractive when the costs of water are covered and the pricing impact of the policies conform to societal notions of fairness or equity. As a general rule, the prescription for pricing water in water-scarce regions is to set the price of water equal to the marginal cost of supplying the last unit delivered (Hirshleifer et al., 1960; Russell and Shin, 1996). As long as marginal costs are higher than average costs—which is usually the case where water is quite scarce—the use of marginal cost pricing will ensure that revenue requirements are met. Marginal cost pricing will also ensure that appropriate signals are sent to consumers about the true cost of the water and given some fixed level of benefits, will ensure that the costs of providing the water are minimized.

Time-of-use pricing, which is an amalgam of marginal cost and average cost pricing, sets the rate higher during periods of peak use to ration water during these periods, but sets lower prices during off-peak or off-season periods of uses. This kind of pricing structure tends to discourage use during peak use periods and encourage use during off-peak periods, and is particularly useful in shifting use away from peak to off-peak use periods. In regions with Mediterranean climates, time-of-use pricing might call for higher prices during the dry season, when use tends to be high, and lower prices during the wet seasons, when supplies are more plentiful and use tends to be lower (Sexton et al., 1989).

Water surcharges are frequently employed to discourage excessive use. That is, a surcharge is imposed above some specified use level to discourage additional use beyond that level. Surcharges are appropriate

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

where water can be effectively rationed by reducing excessive use. Policies that include surcharges are frequently adopted to promote fairness.

Pricing policies that encourage conservation, including marginal cost pricing, time-of-use pricing, and water surcharges, generally work best where the quantity of water demanded is reasonably responsive to price. Thus, for example, where existing water supplies are insufficient or barely sufficient to serve basic drinking, cooking, and sanitation uses, an increase in water prices is unlikely to be effective in achieving water conservation. Conversely, where water is used in discretionary ways, as for irrigating urban landscapes or for low-valued agricultural or industrial purposes, the imposition of rate structures that approximate marginal cost pricing may lead to significant and cost-effective water conservation. Similarly, time-of-use pricing may not lead to water conservation in the aggregate, but may be effective in shifting demand use away from peak to off-peak periods, thereby avoiding the expense of constructing new facilities that would be used to serve peak period uses only.

While pricing policies alone can ensure efficient allocation of water within a service area or within a particular water-using sector, pricing policies alone may not be sufficient to ensure efficient allocation of water among the various water-using sectors. Water markets that include several sectors, and which use marginal cost prices, can be used to allocate water among the sectors in an efficient manner.

Markets have the advantage of permitting transfers of water to occur on a strictly voluntary basis. That is, sellers have an incentive to sell or lease water only when the returns they receive meet or exceed the returns they could earn by putting the water to some other use. Buyers have an incentive to participate in market exchanges only when a purchase or lease represents the least costly opportunity to obtain additional water. Market transfers of water occur when the difference between the minimum price that sellers will accept and the maximum price that buyers will offer is enough to cover any costs of transport or treatment that may be needed to effect the exchange.

Free market arrangements to transfer and reallocate water are frequently criticized for failing to take into account the legitimate interests of other parties who are not directly involved in the transactions but who do nevertheless incur costs because of the transfer (NRC, 1992). Studies of the third-party impacts of market transfers during the California drought show that, in the short run at least, such impacts are likely to be relatively modest. Moreover, in regions or locales where such impacts are significant, they can be attenuated by restricting the quantities of water that can be transferred to perhaps 15 percent of the total water available in the area (Carter et al., 1994). Other studies have led to identifying a broad range of

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

alternatives for managing and minimizing the third-party impacts of marketlike water transfers (NRC, 1992).

Even if water markets are never developed and adopted, simulation studies of water markets can be highly useful in identifying the value of water in alternative uses and regions and in identifying additional water supply and conveyance facilities that are economically justified. One such study, now being conducted under the auspices of the Institute for Social and Economic Policy in the Middle East at Harvard University, provides a number of valuable conclusions (Fisher et al., 1996). Among the tentative conclusions of this study are (1) the value of the water of the Middle East that is in dispute is relatively modest (approximately US$125 million annually); (2) conveyance facilities will need to be built to serve the growing demands of Amman and the northern highlands of Jordan prior to 2010 to avoid a water supply crisis; (3) conveyance facilities should be built to connect the districts of the northern West Bank, and a large-scale conveyance system to take water to the interconnected West Bank districts should also be constructed; (4) the Gaza Strip should be served via an expanded connection to Israel's National Water Carrier; and (5) desalination will not be economically efficient on the Mediterranean coast until at least 2020.

Where water pricing practices are employed to ensure that water is used as efficiently as possible, the policies supporting such practices may be relatively attractive when evaluated against the committee's five criteria, as Table 5.3 shows. Although pricing practices do not augment available water supplies, they are technically feasible and, where they result in a net savings of water, tend to preserve water resources now and for future generations. The economic feasibility of pricing policies will vary from situation to situation, depending on price and income elasticities, which may vary throughout the region. The environmental implications of such policies will also have to be assessed on a case-by-case basis, since policies that result in the conservation of water that might otherwise support amenity uses (such as providing water for streams or wetlands) may have adverse impacts on the natural environment.

Augmenting Available Supplies

Demand management alone may not be sufficient to achieve efficient and equitable allocation of water resources in the study area. This is not to say that efforts at reducing demand are futile—new sources will be expensive and, in some cases, will furnish water of a lower quality. Demand management and supply augmentation will likely both be needed to meet the future human and environmental water requirements.

Additional regional water supplies can be obtained by using what

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

little naturally occurring freshwater is unused (through watershed management, water harvesting, and the development of nonrenewable water), by reusing water (wastewater reclamation), by developing sources of lower water quality (marginal quality water and desalinated brackish water and seawater), by importing water from outside the study area, by transferring water within the study area (though imports and transfers are not analyzed in this report), and by attempting to increase the renewable amount of water available (cloud seeding). These options are reviewed in the following sections, along with the results of the committee's preliminary evaluations of each option based on its five criteria (see Chapter 3). Before these discussions, however, the significance of maintaining water quality is discussed to highlight the importance the committee attaches to this issue.

Maintaining Water Quality

Because the availability of adequate quantities of water in the study area is inextricably bound up with issues of water quality, maintaining water quality is discussed here. The quality of the region's water supplies has been deteriorating for some time, and continued deterioration will only make the problem of water availability worse and more expensive to solve. This trend in water quality must be reversed if there is any hope of solving the water problems of the region. Any strategy to solve the area's water problems must include components to preserve and enhance the quality of water already available.

Deterioration of the natural quality of ground and surface water has been brought about by urban, agricultural, and industrial sector activities. Some of these many human activities that affect water quality include the following:

  • Discharge of inadequately treated effluent from municipal treatment plants.
  • Discharge of untreated domestic and agricultural wastes.
  • Discharge of untreated or inadequately treated industrial wastes.
  • Extraction, use, and disposal of poor-quality ground water.
  • Leachate from solid waste landfills.
  • Runoff from urban drainage.
  • Peak wastewater flows bypassing wastewater treatment plants.
  • Fertilizer and pesticide residues.
  • Saline agricultural return flows.
  • Drainage of wetlands.

It is common engineering and environmental knowledge that prevention

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

is preferable to remediation. Industrial and municipal treatment facilities must be built to solve current pollution problems and keep up with anticipated population and industrial growth. Other measures, such as regulation of pesticides and fertilizers, and proper siting and construction of solid waste landfills, are standard water-quality protection measures that should be vigorously adopted in the study area. Total watershed management should also be adopted (see next section).

Because of the emphasis currently given to the use of reclaimed wastewater in the study area, it is of some value to look more closely at the water-quality implications of this practice. Treated municipal effluent contains many undesirable constituents. Treatment to remove these constituents is successful to varying degrees, depending on the type of treatment and also on the intended reuse of the treated effluent. In urban usage of water, biodegradable organic matter—as measured by biochemical oxygen demand (BOD), chemical oxygen demand (COD), or total organic carbon (TOC)—is added to water. Sewage treatment processes, depending on their intensity, reduce the organic matter content to almost any desired level. This level is dictated by the intended use of the effluent. Effluent may also contain trace concentrations of toxic, stable organic substances, such as pesticides and chlorinated hydrocarbons, which are considerably more difficult to remove.

Pathogenic microorganisms (bacteria and viruses) and parasitic organisms, such as protozoa and helminths, are also present in sewage effluent. Their concentration is greatly reduced during normal treatment processes. Suspended solids, including volatile and fixed solids, are present in municipal effluent, and if not adequately removed can shield microorganisms from disinfection during treatment. Disinfection with chlorine can transform organic compounds present in wastewater into chlorinated organic compounds such as chloroform. These compounds have been implicated in the development of liver, bladder, and kidney cancers. These compounds may be further enhanced if the effluent reaches potable water sources that are normally subjected to further chlorination before use.

Urban use invariably results in increased inorganic soluble salts. The principal ions picked up are sodium (Na+), chloride (Cl-), calcium (Ca+), and sulfate (SO4=). These ions increase the total salt content (salinity) and the sodium adsorption ratio of the water. Unlike organic constituents, inorganic salts are not removed during conventional reclamation processes. Irrigation with water enriched in inorganic salts results in soil salinization and increased salinity of underlying aquifers and surface waters. Thus, irrigation, like many other uses of water, degrades water quality for later uses. Municipal effluent also contains increased quantities of nitrogen (N) and phosphorus (P), which are not significantly removed

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

except in tertiary treatment. These elements in wastewater may increase the value of the water for irrigation, but they increase its pollution and eutrophication. Not all of the fertilizer value can be used, especially because irrigation late in the season often occurs at a period when consumption of nutrients by plants is low. The soil profile is thus enriched with nutrients subsequently leached by winter rain into the ground water.

Water quantity and water quality, again, are very closely related. Reductions in water quality can reduce the available supplies for almost any use just as drought does. In addition, it is almost always cheaper to prevent deterioration of water quality in the first place than to remediate the problem once deterioration has occurred. Maintaining water quality in effect augments available water supplies. In many instances, measures to maintain water quality are technically feasible. Economic feasibility varies with the situation and with the technology or management protocols employed. Environmental quality will almost always be maintained or improved through efforts to maintain water quality. Finally, active maintenance of water quality will almost always benefit both present and future generations.

Watershed Management

Watershed management is defined as the art and science of managing the land, vegetation, and water resources of a drainage basin to control the quality, quantity, and timing of water for enhancing and preserving human welfare and nature. By altering the natural hydrologic cycle, the physical diversion of water often has undesired environmental consequences. This effect can best be illustrated by looking at the consequences of existing regional large-scale water supply projects. The management of Lake Kinneret/Lake Tiberias/Sea of Galilee as a major water supply reservoir and the diversion of the Yarmouk River have almost eliminated the inflow of freshwater to the lower Jordan River. The river has become saline, with a resulting loss of freshwater flora and fauna. Similarly, development of ground-water supplies near the Azraq Oasis in eastern Jordan has eliminated the flow of the two freshwater springs feeding the oasis (Salameh and Bannayan, 1993), again with the resulting loss of freshwater flora and fauna. Drainage of the lake and marshes in the Hula Valley in northern Israel resulted in soil oxidation and subsidence, as well as the loss of native fauna and flora.

With increasing environmental awareness in the study area, the societal and environmental impact of watershed management, as indeed of all schemes to increase water supplies, has become an essential consideration

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

in the planning process. The committee believes that a larger landscape approach is essential for true watershed management.

Dams

Most watershed management schemes in the area involve small-scale efforts to capture stormwater runoff in dams, ponds, or retention basins. Stormwater runoff in the study area is intermittent and highly variable spatially as well as temporally. In rainy years the runoff can reach hundreds of million m3/yr, while in dry years it can be negligible. Almost all of the wadis in the Jordan Valley that drain to the Dead Sea, all of the wadis in the Rift Valley south of the Dead Sea, and many of the wadis draining to the Jordan River are not dammed. Some of the wadis, particularly in the south, contain brackish ground-water discharge in their lower reaches, but in their middle and upper reaches all the wadis are dry except during and immediately following storms. Whenever possible, decisions concerning the management of the area's water resources should not be made on a small-scale, short-term, site-by-site basis, but instead to promote the long-term sustainability of all aquatic resources in the landscape.

Large dams in the wadis, such as the King Talal Dam on the Zarka River, generally cannot be filled with water generated within their own watershed areas (Salameh and Bannayan, 1993, p. 22). They can only be managed efficiently if water is imported into the watershed, and thus will likely be limited to the northern, more developed parts of the study area. The quality of water stored in multisource reservoirs needs to be considered during the planning phase, because it may affect the usefulness of the stored water. The King Talal Reservoir contains stormwater runoff (some of which originates in the Amman area), spring water (some of which is saline), and both treated and untreated sewage effluent. The reservoir was originally planned for potable water for the Amman area, but because of the poor quality of the water, its use is now restricted to irrigation in the Jordan River Valley. Similarly, the Baruch Reservoir in the Yezreel Valley in Israel contains treated wastewater and saline spring discharge as well as stormwater. This reservoir and some small ponds in the valley have created a severe drainage and salinity problem (Binyamin et al., 1991). One option to increase the reliable water supply from the Yarmouk River is to construct the proposed Unity Dam. However, the committee did not analyze this option because it involves issues beyond the scope of its study.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×
Small Retention Structures

In contrast to large dams, small retention structures on the wadis could possibly be effective in capturing stormwater runoff. In Israel, the quantity of stormwater runoff that can be captured is estimated at 160 million m3/yr (Soffer, 1992). Presently, only 25 percent of this water is intercepted or stored underground, in approximately 120 small open reservoirs spread throughout the country. The total storage capacity of these reservoirs is about 100 million m3, sufficient to store most of the available runoff from the watersheds.

According to the Palestinian Water Authority, the quantity of stormwater runoff in the West Bank is 70 million m3/yr. Only 2 million m3/yr of stormwater runoff is generated within the Gaza Strip, although floodwaters originating in Israel make the total available runoff about 15 million m3/yr. None of this water is presently intercepted, but several feasibility studies are being considered. An estimated 13 to 15 million m3/yr (BRL-ANTEA, 1995) could be captured through construction of storage structures on four of the principal wadis draining eastward in the West Bank (Wadis Fara'a, Badan, Maleh, and Qilt). Studies have also begun on recharging captured flows in Wadi Gaza into the coastal aquifer.

About 40 million m3/yr of stormwater runoff may be available from wadis in Jordan that are tributary to the Jordan-Dead Sea-Rift valley (Open files, Water Authority of Jordan). Pilot projects on four of the wadis are under way (Kifaya, 1991) to test the feasibility of constructing small retention structures.

The utility of water stored behind retention structures in many of area wadis will be limited by the structures' remoteness from urban and agricultural areas and the fact that they will likely hold water only for a short period of time. If the water they capture is not used shortly after storms, much if not all of the water will be lost to evaporation, transpiration, and seepage, and will therefore be unavailable during the dry season. One possibility is thus to use retained stormwater for artificial recharge. This strategy has proven practical for recharging unconfined aquifers in arid areas (U.S. Army Corps of Engineers, 1979). Several stormwater interception projects in Israel are used to recharge ground water (although none presently in the eastward-draining wadis). Among existing projects are the Shiqma Reservoir in the south and the Menashe project in the north. These projects utilize infiltration of retained stormwater to recharge shallow, unconfined aquifers. Stormwater might also be used for the irrigation of single trees or small fields in the arid southern part of the study area.

Although direct infiltration to unconfined aquifers may not be possible at many potential stormwater retention sites, recharge to underlying

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

confined aquifers by means of injection wells may be a possibility. Where head relationships are suitable, recharge could be accomplished by gravity drainage, which would be a major advantage in remote areas. Particularly in the wadis draining toward the Rift Valley, the recharged water would most likely create a storage zone of fresher water (compared to ambient water quality in the aquifer), which could be withdrawn when needed. This process is called aquifer storage and recovery. Problems of sediment removal and clogging of wells would need to be studied.

Urban runoff is another source of water for retention basins. Impervious urban areas in arid environments can sporadically generate large quantities of runoff, which, depending on the degree of treatment, can be used for various types of irrigation or for ground-water recharge (Ishaq and Khararjian, 1988).

However, urban runoff, especially from industrial areas, may not be suitable for ground-water recharge and further treatment before recharge may be necessary. Current practices within the study area are to convey urban stormwater to natural drainage outlets or to collect it in the sanitary sewer system. Retention basins, in addition to storing usable water, would therefore attenuate flooding and avoid excess flows at wastewater treatment plants. Finding suitable locations in urban areas may be a problem, and retrofitting existing collection systems would be expensive. However, the expansion of existing urban areas and the possible creation of new urban centers to accommodate regional population growth afford the opportunity to plan for alternative and beneficial uses of urban stormwater runoff. Planning should involve consideration of the treatment required to make the water suitable for its intended use, and the downstream environmental effects of diverting storm runoff away from natural drainage ways.

Altering the Hydrologic Cycle

Methods for decreasing evapotranspiration, increasing natural ground-water recharge, and decreasing natural ground-water discharge, although less common than the capture of stormwater runoff, are other possible watershed management options. Evapotranspiration rates are highest in wetlands and over open water bodies. The drainage of the Hula Wetlands in northern Israel to create arable land and the near elimination of the Azraq Oasis by ground-water pumping are examples of unintentional decreases in evapotranspiration, with equally unintentional environmental consequences. (See Boxes 4.1 and 4.2) Thus, the elimination or reduction of wetlands and open water bodies, although immediately attractive to meet water demand, will almost always have a negative

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

effect on biodiversity and the natural functioning of the ecological system and should therefore be approached with caution.

Natural recharge can be increased by dewatering aquifers that have natural water tables within one or two meters of land surface. Not only will this approach decrease evapotranspiration, but potential recharge formerly rejected by the aquifer when the ground or soil was saturated will now be able to infiltrate into the aquifer. Such planned management schemes are related to and have similar environmental consequences as other schemes to decrease evapotranspiration.

Pumping of ground water results in a reduction of natural discharge and a decrease in water levels (pressure) within the aquifer. In aquifers adjacent to brackish or saline water, the decline in pressure results in the movement of this poorer quality water into the freshwater part of the aquifer. In the study area, lateral movement of seawater has occurred in the coastal aquifers in Israel and the Gaza Strip (Palestinian Water Authority, MOPIC, 1996), and upward migration of saline water has occurred in the aquifers underlying the Dhuleil and Badia areas in Jordan (Salameh and Bannayan, 1993). Projects to intentionally decrease ground-water discharge should be carefully evaluated on the basis of predictable hydrologic consequences. However, on a small scale and with suitable physical conditions, ground-water discharge may be decreased and water levels increased by the construction of underground dams (Nilsson, 1988). Mediterranean coastal areas underlain by thin, unconfined sand aquifers might be particularly suited to this technology, which generally involves the construction, by injection through closely spaced boreholes, of a cement or low-permeability grout curtain extending to the base of the aquifer. In addition to storing ground water, underground dams can also prevent the lateral intrusion of saline water into coastal aquifers (Garagunis, 1981). Another method is keeping a water table mound along the coast while lowering the water table by pumping further away from the coast, a method successfully used in the coastal aquifer of Israel.

The attractiveness of watershed management will depend critically on the local circumstances and the management measures proposed. Table 5.5 summarizes the potential of watershed management measures in view of the five committee criteria. In most instances, watershed management will increase available water supplies. Situations in which management measures are undertaken to improve water quality may be an exception. There are a whole array of technically feasible watershed management techniques, whose economic feasibility will vary from situation to situation, depending in part on the value of the additional increments of water produced. The environmental impacts of watershed management will also be situation-specific. In general, where watersheds are managed to improve or maintain water quality, the environmental impact

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.5 Augmenting Supplies

Committee Criterion

Watershed Management

Water Harvesting

Ground-Water Overdraft

1.

Impact on Available Water Supply

+/-

+

+ (short term)

- (long term)

2.

Technically Feasible

+

+/-

+

3.

Environmental Impact

+/-

+/-

-

4.

Economically Feasible

+/-

+/-

+ (short term

- (long term)

5

Implications for Intergenerational Equity

+

?

-

NOTE: + indicates positive effects, - indicates negative effects.

will be salutary. Where watershed management involves the construction of large dams, environmental impacts may be negative. Finally, inasmuch as watershed management activities enhance the quantity or the quality of water available, or both, the impact on present and future generations will likely be positive.

Water Harvesting

Rainfall is the ultimate source of all freshwater in the study area. The direct capture of rainfall is referred to as water harvesting. The most common methods of water harvesting are the use of rooftop cisterns for individual domestic supplies, and catchment systems and storage ponds for agricultural supplies. Cisterns are used throughout the world for rural water supplies, and they are particularly common in villages within the West Bank (Anonymous, 1988). Investigations by the Palestinian Hydrology Group (PHG, 1992) and Bargouthi and Deibes (1993) indicate that 45 percent of the rural areas (37 percent of the population) in the West Bank depend on rainwater harvesting to satisfy their basic water needs. The increased use of cisterns for domestic supply has been suggested for the Gaza Strip (Abu-Safieh, 1991) and Jordan (Tekeli and Mahmood, 1987).

Cisterns used in the West Bank and Gaza Strip are generally small excavations in the ground, generally no more than 6 m in depth. They are of various shapes but the traditional shape is like an inverted cone, or najasa, meaning pear-shaped. A typical cistern can store 70 to 100 m3 of rainfall, which is accumulated from rooftop catchments during the winter. This quantity is sufficient to satisfy the needs of a family of five for the dry summer months. Moreover, the cost of this water is almost zero, if the initial cost of construction is not considered. Even with construction

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

costs, however, the cost of cistern water will remain cheaper than water purchased from the conventional water distribution system or from water tanks in areas not served by distribution systems. For example, the Palestinian Hydrology Group (PHG, 1995) has reported that a cistern can save an average family 1,000 to 1,500 NIS annually (about 12.5 percent of its annual income). Even where conventional sources of water are available, cisterns can provide supplemental water inexpensively and relieve the demand on the water distribution system.

In rainfall catchment systems, quality problems may be associated with the first water to enter the cistern (''the first flush") following the onset of rainfall (Yaziz et al., 1989). However, various methods, such as first-flush diversion devices, roof maintenance, removal of overhanging vegetation, and installation of screens, can be used to protect and improve the quality of the stored water (Krishna, 1991). Other technologies are also available to provide point-of-use (at the tap) or point-of-entry (at the house) treatment (Rozelle, 1987), as described later in this chapter.

The expansion of existing urban areas and possible creation of new urban centers in the study area may allow rainfall collection systems to be incorporated into housing designs. Large-scale urban construction projects can incorporate systems to convey water from rooftop catchments to centralized treatment plants for inclusion in municipal water supplies.

The use of ponds to store rainfall for livestock and irrigation is common in the Gaza Strip. These ponds are generally cubic or trapezoidal, with volumes of as much as 300 m3 for cement ponds and as much as 3,000 m3 for earthen or plastic ponds. Use of the ponds has partially replaced pumping from the shallow aquifer in the Gaza Strip and has helped prevent further deterioration of ground-water quality. In some cases, brackish ground water is mixed with collected rainwater to produce water that is suitable for irrigation. The use of these ponds as a source of water for artificial recharge in the Gaza Strip has been suggested by Al-Khodari (1991). Agricultural and artificial recharge designs that incorporate both water harvesting and the capture of stormwater runoff may also prove feasible in the study area.

The promise of water-harvesting options is very situation-specific, varying with both location and the particular activity proposed. As indicated in Table 5.5 water harvesting by its very nature will augment the available water supply. However, technical and economic feasibility and likely environmental impacts cannot be readily judged without more detailed information about the particular water-harvesting measure and the place it will be used. It is difficult to assess the implications of this approach for future generations in the absence of specific details.

In the 1950s, it was demonstrated in the Negev Desert that a system of capturing low natural rainfall without irrigation was technically feasible

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

for growing food crops (Amiran, 1965; Evanari et al., 1982). This was a system developed by Nabatean and later Byzantine farmers in the first millennium A.D. that later fell into disrepair, and is no longer regarded as economic. It involves arrangements of cisterns, channels, soil, rocks, and plants to maximize the amount of rainwater available to plants during their growing season.

Ground-Water Overdraft

Because of the temporal variability of ground-water recharge, extraction of ground water by pumping almost always results in at least a seasonal decrease in the resources quantity, but this quantity will fluctuate around the long-term average and, if extraction does not exceed recharge, the supply is sustainable. If, on the other hand, extraction rates continually exceed recharge rates, ground-water levels will decline and the aquifer is overexploited. The amount of extracted water that exceeds the recharge rate represents a nonrenewable resource.

Ground-water overdraft is significant in Jordan, for example the Azraq Basin (Box 4.1), and efforts should be made to avoid further depletion of the resource. Future water supply scenarios in the area (CES Consulting Engineers and GTZ [Association for Technical Cooperation], 1996) indicate an overall reduction in conventional (renewable) ground-water withdrawals west of the Jordan River (Table 5.6). Ground-water mining of an aquifer that is hydraulically connected to a saline water body, such as saline ground water or seawater, will result not only in depleting the resource, but in degrading the quality of the freshwater. Overexploitation of the coastal aquifer in Israel and the Gaza Strip, for example, has resulted in the landward encroachment of saline water. Because of the almost immediate environmental consequences of ground-water overdraft and the eventual environmental and water quality consequences of the total depletion of the resource, attempting to reduce extraction rates from overexploited aquifers should be a high priority in the study area.

With proper management, most aquifers can provide a sustainable water supply and the basis for maintaining ecosystem biodiversity, as long as they are recharged. To ensure the sustainability of this ground-water use, research is needed on the amount of water held in storage and the environmental consequences of depleting this storage. More consideration also needs to be given to beneficially using the storage space created by ground-water mining. This space can be utilized to store freshwater from a variety of sources through artificial recharge. Freshwater from remote sources and treated wastewater have been used to artificially recharge the coastal aquifer in Israel. In addition to being stored in

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.6 Consolidated Conventional Water Resources

Sub-region

Current Surface Water Developed (million m3/yr)

Future Surface Water Developed (million m3/yr)

Current Ground Water Developed (million m3/yr)

Future Ground Water Developed (million m3/yr)

Current Total Water Resource (million m3/yr)

Total Water Resource (million m3/yr)

West of JRV

685

725

1,234

1,299

1,919

2,024

East of JRV

290

475

535

488

825

963

Total Study Area

975

1,200

1,769

1,787

2,744

2,987

NOTE: JRV, Jordan Rift Valley; Future, Year 2040.

SOURCE: Reprinted, with permission, from CES Consulting Engineers and GTZ, 1996. ©1996 by Consulting Engineers Salzgitter GmbH.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

the aquifer for later use, this water has also been used to control water quality degradation in the aquifer. Similar schemes have been proposed for the coastal aquifer in the Gaza Strip and elsewhere (Assaf, 1994).

A special case of overexploitation occurs in aquifers that receive little or no recharge. Water contained in such aquifers is referred to as "fossil" water and is considered a totally nonrenewable resource. The Disi Aquifer in southern Jordan and the Nubian Sandstone Aquifer in southern Israel are the principal geologic units containing fossil water in the study area. These thick sandstone sequences were filled with freshwater during the geologic past, when climatic and geologic conditions were more favorable for recharge. They currently receive little or no recharge.

It is estimated that billions of m3 of good to excellent quality water are stored in the Disi and Nubian aquifers. According to the Multilateral Working Group on Water Resources (CES Consulting Engineers and GTZ, 1996) 253 million m3/yr of fossil ground water are projected to be available in the study area (110 million m3/yr west of the Rift Valley and 143 million m3/yr east of the valley). This rate of withdrawal would indicate a "life expectancy" of the resource measurable in hundreds of years. Current withdrawals are at the rate of 95 million m3/yr (25 million m3/yr west of the Rift Valley and 70 million m3/yr east of the valley). However, the consequences of the current or higher withdrawal rates are largely unknown.

What is known is that as water is withdrawn from aquifers containing fossil water, a continual decline in water levels occurs. This decline induces saline or brackish water from adjacent rocks to move into the aquifers to replace the freshwater removed from storage. In addition freshwater from overlying aquifers may be induced to move into the fossil aquifer. Research is needed on how these phenomena will affect the sustainability of water resources in the study area. The extraction of fossil ground water may not have significant environmental consequences because the aquifers are isolated from the biosphere and have little or no natural recharge or discharge. However, because this resource represents the largest untapped water resource in the study area, it should be developed within the framework of an overall sustainable development scheme. Options for the development of fossil ground water include use for local development (the current practice), use as part of a national or regional distribution system, or retention as a reserve water supply. An economic analysis of the consequences of the development or deferred development of fossil ground water needs to be made. Such an analysis should be based on hydrologic research and should include consideration of the environment and the protection of future generations. As mentioned in Chapter 2, temporary overpumping in an aquifer can provide time for transition to a nonagricultural economy.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

As shown in Table 5.5 ground-water overdraft is not an especially attractive means of augmenting supplies, except in some special circumstances. Ground-water overdraft is always self-terminating, as water levels ultimately decline to depths from which it is no longer economical to pump. Thus, ground-water overdraft can augment available water supplies in the short run but if overdraft persists, the quantities of water available decline. Ground-water overdraft is technically feasible, except where the depth to the water table is very great. The environmental impacts of ground-water overdraft, such as subsidence and seawater intrusion, are almost always negative.

The economic feasibility of overdraft varies over the period of exploitation. In the short term, there may be temporary circumstances, such as the need to combat drought, when overdrafting may be economically feasible and economically optimal. However, overdrafting is not economically optimal over long periods of time, and ultimately it becomes economically infeasible when water tables are drawn down to levels from which it is not economical to pump. Overdrafting will almost always have negative impacts for future generations, since the stock of ground water left for future generations will always be smaller than if overdrafting had not occurred in the first place.

Wastewater Reclamation

Clearly, water is too precious a commodity within the study area to be used only once and then discarded as a waste product (similar U.S. areas are discussed in Boxes 5.2 and 5.3). Indeed, the study area already is a leader in the use of reclaimed wastewater for nonpotable use. About 53 percent of the total urban (domestic) water used in the area receives some form of treatment after use. In Israel, about 70 percent of all the effluent from municipal wastewater treatment plants is recycled (Argaman, 1989). In Jordan, about 60 percent is recycled (WAJ files). Almost none is being treated in the West Bank, and nearly 20 million m3/yr is treated in the Gaza Strip. As the demand for water continues to increase beyond the available natural supply, it is not unreasonable for water supply plans to forecast a near-total reuse of water in the study area.

Reclamation has two benefits. The first is pollution abatement—the elimination of wastewater as an environmental and health hazard. The second is source substitution—an increase in the net amount of water available for use (U.S. EPA, 1992). For this reason, wastewater reclamation is more common in arid and semiarid dry regions and countries, such as Australia, the western United States, Mexico, the Arabian Peninsula, South Africa, India, Cyprus, Tunisia, and Israel.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

BOX 5.2 Harlingen, Texas: The Importance of Source Water in Industrial Reuse

The city of Harlingen, Texas, is located 16 km north of the U.S.-Mexican border in the southern tip of Texas. In 1988, the city recognized that it needed additional water supplies if it was to attract new industry to create additional employment and increase tax revenues. The city undertook a study to identify alternative means of increasing the water supply, and three were identified. First, it could purchase potable water from neighboring communities, but at a very high price. Second, it could acquire low-quality irrigation water supplies from nearby growers. Third, it could reuse treated municipal wastewater. Domestic wastewater reuse was found to be the most cost-effective source of additional supply, despite the fact that existing treatment facilities would have to be modified and some new facilities constructed.

The city was fortunate in that existing wastewater streams could be segregated at very low cost. Existing industrial wastewater was of very low quality, with prevailing total dissolved solids levels so high that treatment with reverse osmosis was not feasible. Domestic wastewater, on the other hand, was of sufficiently high quality that reverse osmosis could be used to produce relatively high-quality source water for industrial use. In this case, the key to the cost-effectiveness of the wastewater reuse system lay in the fact that existing sewer and wastewater disposal systems did not have to be retrofit in order to separate domestic and industrial wastewater streams. Had retrofit been necessary, the plan would not have been cost-effective.

The plan ultimately adopted entailed conventional treatment of domestic wastewater, followed by coagulation and filtration to reduce suspended solids, and reverse osmosis. Industrial waste was treated in a new and separate facility and discharged. The new wastewater reuse system was placed in operation in 1992. This reuse facility produced 7,400 m3/day of demineralized water at a unit cost of $0.23/m3. The capital costs of the project totaled $9.5 million, while annual operating costs amounted to $400,000. The experience at Harlingen illustrates the importance of source water quality in determining whether wastewater reclamation and reuse schemes can be feasible and cost-effective.

Reclamation will also serve to increase the usable amount of any additional supplies obtained from other sources of freshwater. For example, 50 million m3 of fossil water used for municipal supply can result in an additional 35 million m3 reclaimed water (assuming a 30 percent reduction due to conveyance losses and consumptive use).

There are three categories of wastewater reclamation: (1) direct use of wastewater with little or no treatment; (2) direct use of wastewater after suitable treatment; and (3) the indirect use of treated effluent after suitable treatment.

Direct Use of Untreated Wastewater

Some types of untreated wastewater, such as wash water from washing machines and kitchen sinks (so-called "gray water") can be used directly

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

BOX 5.3 Multiple Use of Reclaimed Wastewater in Southern California

The West Basin Municipal Water District wholesales water supplies for some 900,000 residents and a large number of industries on the western side of the Los Angeles Basin. Throughout its history, the district has been confronted with an acute scarcity of local supplies and high cost and scarcity of imported supplies. With several other water purveyors in southern California, the West Basin District has been an innovator in utilizing reclaimed wastewater to meet the demands of its customers. In recent years, the incentive to employ wastewater reclamation has been strengthened, as coastal communities in southern California have come under intensifying pressure to reduce the quantity of wastewater discharged to the Pacific Ocean. This pressure has worked to the advantage of the West Basin Municipal Water District, because its service area lies in proximity to the Hyperion Wastewater Treatment Plant, the largest treatment plant of the City of Los Angeles.

The West Basin District has embarked on a decade-long project that will ultimately reclaim 86 million m3 of wastewater annually. The first phase of this project, to be completed shortly, will yield 20.5 million m3 annually. Initially, product water will be distributed evenly among three different uses. Three treatment streams have been designed to match the quality of the product water for each of the uses. The first, and ultimately largest, use is for seawater intrusion control. These waters are injected into the West Basin Aquifer to form a freshwater barrier between inland ground water and intruding seawater. The barrier injection water will undergo biological denitrification, softening, pH adjustment, filtration, reverse osmosis, and disinfection. The product water will meet all state standards for drinking water.

Second, a portion of the reclaimed water will be used for industrial purposes. Two large oil refineries will use product water as a cooling water makeup source, and for boiler feedwater and other process uses. This water will be denitrified, softened, filtered, and disinfected, and will meet standards for industrial use in petroleum refining. Third, product water will also be used for public landscape irrigation. Over 1,200 users have been identified, including public parks, schools, cemeteries, and golf courses. Treatment for this use consists of coagulation, flocculation, filtration, and disinfection. This product water will meet all state requirements for unrestricted irrigation reuse of wastewater. The unit cost of the water averaged across all uses is $0.57 m3, which is considerably less expensive than alternative sources of supply.

The West Basin Water Reclamation Program illustrates how a large wastewater reclamation project can be tailored to serve a number of uses, each requiring a different level of water quality. In general, such multiple-purpose projects will be most economical where large quantities of wastewater are available for reclamation, allowing economies of scale to be realized.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

in homes for toilet flushing or garden irrigation. Gray water can contain contaminants that are harmful to humans, and therefore care is needed in separating gray water plumbing from potable water plumbing.

Direct use of untreated wastewater is possible in some industries by in-plant industrial recycling; its adoption can be encouraged by pricing or permitting policies for water supplied to industries and by imposing quality standards and impact fees on industrial effluent. Water quality requirements of individual industrial applications will determine the practicality of direct reuse. Another possibility for direct reuse is the reapplication of agricultural drainage (return flow) for irrigation. For agricultural applications, the quantity of directly reused water will be limited by water quality considerations, although blending or cycling drainage water with better quality water can increase its usefulness (Grattan and Rhoads, 1990).

Direct Use of Treated Wastewater

Although it is technologically possible, treated wastewater is not used directly for potable supplies, because the public generally does not accept the concept (U.S. EPA, 1992, p.106). Nevertheless, after suitable treatment, wastewater is used directly for many nonpotable uses in all three major sectors: urban, agricultural, and industrial. Table 5.7 shows the physical and chemical characteristics of the effluent from the Dan District treatment facility (Shafdan) in Israel following infiltration and pumping

TABLE 5.7 Quality of Effluent Following Advanced Treatment (Soil Aquifer Treatment) the Shafdan Project, Israela

Parameter

Unit

Post-Treatment Value

Total dissolved solids

mg/l

1031

Cl

mg/l

322

Sodium

mg/l

227

EC

ds/m

1.76

SAR

(meg/l)1/2

5.1

Boron

mg/l

0.5

pH

units

7.73

NO3-N

mg/l

5.3

NO2-N

mg/l

2.9

Total N

mg/l

8.8

Alkalinity (as CaCO3)

mg/l

310

a All other parameters—biological oxygen demand, coliform bacteria, viruses, trace elements, trace organics, and toxic substances—were very low.

SOURCE: Reprinted, with permission, from Kanarek et al., 1994. ©1994 by Mekoroth Water Co. Ltd.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

from a shallow aquifer (Soil-Aquifer Treatment). The water is of better quality than the regular drinking-water supply.

Urban

Although reclaimed wastewater will probably not be used as a potable source, it has many other potential urban uses. Urban nonpotable uses include landscape irrigation, toilet flushing, construction, vehicle and street cleaning, fire protection, and air conditioning (Okun, 1994). Urban reuse of wastewater requires dual municipal distribution systems—one for potable water and the other for reclaimed wastewater. Although major retrofitting of existing urban infrastructures would be costly, its cost must be compared to the cost of providing additional potable water from alternative sources. The prospect of major urban expansion in the study area may allow the planning of communities with an initial dual water system. Variability of supply and demand may require storage facilities, and the need for a noninterruptible supply may also require multiple treatment plants (U.S. EPA, 1992). Because urban and industrial effluent is enriched in dissolved solids, repeated wastewater recycling will significantly increase salinity. Although membrane and other expensive treatment processes can remove salts, efforts to minimize the salinization of wastewater are a requirement for sustainable urban recycling.

Agriculture

By far the largest use of reclaimed water is that of the agricultural sector. In Israel in 1994, 254 million m3/yr of reclaimed water was used to irrigate more than 27,000 ha (Table 5.8) (Eitan, 1995); see Box 5.1 for further discussion. This source therefore represents about 65 percent of total agricultural water use. The Israeli Water Commission estimates

TABLE 5.8 Crop Areas Irrigated With Treated Effluent in Israel (ha), 1994

District

Crops

Field Citrus

Crops

Tree Crops

Forage Various

Total

Jerusalem

3,103

0

72

0

0

3,175

North

5,653

106

282

975

92

7,078

Haifa

4,568

121

38

45

0

4,772

Center

4,752

394

65

1,188

102

6,504

Tel Aviv

307

48

17

0

0

372

South

4,157

25

126

1,096

280

5,684

West Bank

16

0

0

0

0

16

Gaza

7

0

6

0

0

13

Total

22,533

694

606

3,304

474

27,611

 

SOURCE: Eitan, 1995.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

that, by the year 2020, 782 million m3 / yr of treated effluent will be produced in the area west of the Jordan River and that 98 percent of this effluent (767 million m3 / yr) will be used for irrigation. In Jordan in 1994, 59 million m3 / yr of reclaimed wastewater was used in irrigation, representing 8 percent of the total agricultural use (see Table 2.3); however, this percentage is expected to increase because Jordanian legislation, strengthened in 1995, requires that all new sewage treatment plants include a provision for reuse of the effluent, with emphasis on expanding agriculture in the eastern uplands (WAJ open files). Irrigation with reclaimed water has been suggested as well for the Gaza Strip and West Bank (Abu Safieh, 1991; Sbeih, 1994), but awaits improvement of wastewater treatment facilities. Currently about 20 million m3 / yr of wastewater are treated in the West Bank and Gaza Strip, but the quantity is expected to increase to about 43 million m3 / yr with sewerage expansion and increased water consumption. Substituting reclaimed for potable water in irrigation obviously allows the more beneficial and efficient use of the limited freshwater sources.

Forage and other crops that are not consumed by humans have the lowest water quality requirements, and for irrigation of these crops, effluent given only primary treatment is sometimes used. Primary treatment includes screening of coarse solids and grit removal, sedimentation of settleable material, and skimming of floatable material. But for most purposes, secondary treatment is required as well. Secondary treatment includes the use of stabilization ponds or aerated lagoons (low-rate processes) or activated sludge, trickling filters, or rotating biological contractors (high-rate processes). Generally, water after disinfection must follow treatment. Water after secondary treatment may be used for crops not directly consumed by humans; in Jordan, however, the quality of wastewater given even secondary treatment may preclude the use of this wastewater effluent on crops. For wide spectrum irrigation, tertiary (advanced) treatment is also required. Advanced treatment removes nitrogen, phosphorus, suspended solids, dissolved organic substances, and metals.

Permissible levels of suspended solids, biological oxygen demand, coliform count, and residual chloride for the irrigation of various categories of crops in Israel are presented in Table 5.9. Obviously, unrestricted irrigation requires higher degree of purification (category D) than irrigation of crops which are utilized only after processing (category A).

Aside from water quality considerations, the major problem in using wastewater for irrigation is the timing of supply and demand. Wastewater is a relatively constant source, whereas irrigation demand is variable. Thus, alternate uses and storage facilities for the treated water must often be included in the design of agricultural reuse projects. Storage facilities also provide for additional treatment of the wastewater. A properly managed

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.9 Quality Criteria for Treated Wastewater Effluent to be Reused for Agricultural Irrigation in Israela

 

Crop Type

 

 

 

 

A

B

Cb

D

Effluent Quality

(cotton, sugar beet, cereals, dry fodder, seeds, forest irrigation)

(green fodder, olives, peanuts, citrus, bananas, almonds, nuts, etc.)

(deciduous fruits, conserved vegetables, greenbelts, football fields, golf courses)

(unrestricted crops, including vegetables eaten uncooked (raw), parks, and lawns)

BOD5,c total (mg/1)

60

45

35

15

BOD5, dissolved (mg/1)

20

10

Suspended solids (mg/1)

50

40

30

15

Dissolved oxygen (mg/1)

0.5

0.5

0.5

0.5

Coliforms counts (100 ml)

250

12 (2.2)d

Residual available chlorine (mg/1)

0.15

0.5

a Requirements should be met in at least 80 percent of samples taken.

b Irrigation must stop 2 weeks before picking; no fruit to be taken from the ground.

c BOD measured or calculated over a 5-day period.

d Requirement should be met in at least 50 percent of samples.

SOURCE: Shelef, 1991.

sequential set of reservoirs can appreciably improve the quality of wastewater (Juanico, 1996). Storage of effluent in aquifers can provide the equivalent of tertiary treatment (Table 5.7; NRC, 1994).

Industry

Industrial uses of water include cooling, boiler-feed, and process water. All three of these uses can take advantage of reclaimed wastewater, although additional treatment, ranging from pH adjustment to carbon-adsorption filtration, may be required. Cooling water generally

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

requires the least treatment and offers the most promise for expanded use of wastewater. Economics and public policy, however, may favor use of reclaimed water in the agricultural and urban sectors.

Indirect Use

Indirect uses of reclaimed wastewater include enhancement of the natural environment, fish farming, and ground-water recharge (U.S. EPA, 1992). Environmental enhancement, such as creation or augmentation of wetlands or lakes, and stream augmentation, requires water treatment commensurate with the degree of human contact with the water. Where sufficient treatment is provided, environmental uses of reclaimed wastewater may provide an alternative method of storing reclaimed water.

Commercial fish production in artificial impoundments of reclaimed water is widely practiced in Israel (Crook, 1990). Where fish are used for human consumption, the quality of the reclaimed water must be of sufficient quality to preclude the bioaccumulation of toxic contaminants (U.S. EPA, 1992).

By far the most significant indirect use of reclaimed water in the study area is for artificial recharge of ground water. Recharge may be accomplished by surface infiltration from impoundments or by injection from wells (NRC, 1994). Currently, only the infiltration method is practiced in the study area. The purposes for recharging ground water with reclaimed water include (1) providing storage for excess reclaimed water, (2) providing additional treatment, (3) replenishing aquifers, and (4) establishing saltwater intrusion barriers in coastal aquifers (U.S. EPA, 1992). These purposes are often synergistic. For example, secondarily treated wastewater from Tel Aviv is used to recharge an unconfined aquifer. Part of the recharge is used to replenish the aquifer, and part is later withdrawn and used for irrigation. Because of the additional treatment the water received within the soil zone and the aquifer, the withdrawn water is suitable for unrestricted irrigation of vegetables that are eaten raw, see Table 5.9 (NRC, 1994).

Ground-water recharge with surface infiltration systems is not feasible where poorly permeable soils are present, land is too costly, unsaturated zones have impermeable layers or contain undesirable chemicals that can leach out, or aquifers have poor quality water at the top or are confined (NRC, 1994). In these cases, ground water may be recharged by means of injection wells. Reclaimed wastewater can be used to replenish depleted, confined aquifers, to store water in brackish or saline aquifers for later withdrawal (referred to as aquifer storage and recovery), or create saltwater intrusion barriers. Repeated recycling of wastewater by means of surface infiltration or injection systems can lead to increases in ground-water salinity.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

A closely related problem here and in connection with the overdraft of ground water is that aquifers in such areas as between Beersheva and the Gaza Strip are being considered for disposal of highly hazardous waste. Deep disposal could cause serious contamination of remaining supplies.

Cost of Reuse

There is sufficient technology and opportunity to allow for the total utilization of reclaimed wastewater in the area for the foreseeable future. The practical feasibility of a particular wastewater reclamation project is determined by its cost, which is dependent on the quantity of water involved, the quality of the source wastewater, and the desired quality of the treated water. Table 5.10 summarizes the characteristics of a number of wastewater reclamation projects in the United States and one in the region under study. For projects where very little treatment is required, such as Phoenix, Arizona, and Whittier and San Clemente, California in the United States, and the Dan Region Project in Israel, the costs are extremely modest. Source water for all of these projects is of relatively high quality and the product waters are used exclusively for ground-water recharge. The projects with relatively high costs, including Water Factory 21 in Southern California and El Paso, Texas, have relatively high treatment requirements. Product water from Water Factory 21 must meet standards for potable use, since drinking water is extracted from the recharged aquifer. In El Paso, raw wastewater must be subjected to primary and secondary treatment prior to the advanced treatment to bring water quality to levels suitable for irrigation, ground-water recharge and industrial uses.

Thus, the costs of wastewater reuse are influenced by public health and environmental standards, which determine how much raw water must be treated prior to discharge. Where standards are high, the incremental cost of the treatment to make the water suitable for nonpotable uses may be quite reasonable (NRC, 1994). Where existing sources of surface and ground water are fully allocated, reclaimed water may also be economically attractive compared to alternative sources, regardless of prevailing wastewater treatment standards. Reclaimed water's economic attractiveness will of course vary depending on the costs of its required treatment and the costs of the alternatives. For this reason, the economics of developing reclaimed wastewater must be assessed case by case.

Table 5.11 summarizes the evaluation of wastewater reclamation against the committee's five criteria. It suggests that wastewater reclamation may be a relatively attractive option for the study area. Like recycling, wastewater reclamation can significantly add to the region's available water supply. Reclamation has proven technologically feasible not

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.10 Costs of Wastewater Reusea

Project Location

Date On Line

Reuse Volume (m3/day)

Phoenix, AZ

1970s

56,800

Whittier, CA

1962

170,000

Dan Region Project, Israel

1977

33,000

San Clemente, CA

1970s

7,600

Harlingen, TX

1990

7,400

Chevron Refinery, CA

1996

18,600

Saudi Arabia

Proposed

292,000

Franklin Canyon, CA

1996

1,600

West Basin, CA

1994

236,000

El Paso, TX

1985

37,900

Water Factory 21, CA

1977

56,800

a Unit costs are in 1996 dollars.

b RW, raw wastewater; 2nd, secondary effluent; 3rd, tertiary effluent.

c 1st, primary treatment; C, chlorination; CP, chemical precipitation; D, disinfection; GAC, granular activated carbon; F, filtration; N, nitrification; OP, oxidation ponds; RO, reverse osmosis; SAT, soil aquifer treatment.

only within the region but in many other places throughout the world. Its environmental impacts are generally positive because it improves water quality in addition to stretching water supplies through reuse. The economic feasibility of reclamation varies with such factors as the quality of the feedwater and the technology used. Reclamation is economically feasible in many circumstances, however, most likely including significant number of reclamation opportunities in the study region. Finally, by maintaining and enhancing water quality and allowing water to be recycled and reused, reclamation is a sustainable practice that will tend to enhance both the quantity and quality of water for present and future generations.

Use of Water of Marginal Quality

An unknown, but possibly significant, savings in freshwater could be obtained by substituting water of marginal quality in some activities that now use potable freshwater. ''Marginal" is, of course, a relative term; reclaimed wastewater, for example, is a special case of marginal quality water. Brackish or saline ground water, in some cases even seawater, may be used for some of the just-described uses of wastewater. The discussion here is limited to brackish water, defined as having a chloride

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

Project Location

Source Water Qualityb

Project Treatmentc

Type of Reused

Unit Cost ($/m3)

Phoenix, AZ

2nd

None

GW

0.01

Whittier, CA

3rd

None

GW

0.02

Dan Region Project, Israel

RW

OP, 2nd, SAT

GW

0.03e

San Clemente, CA

2nd

F

GW

0.05

Harlingen, TX

2nd

F, RO, D

IN

0.27

Chevron Refinery, CA

2nd

CP, F, D

IN

0.44

Saudi Arabia

2nd

Variable

IR, IN, GW

0.18-0.42

Franklin Canyon, CA

2nd

CD

IR

0.46

West Basin, CA

3rd

N, F, RO, D

IR, IN, GW

0.57

El Paso, TX

RW

1st, CP, F, D, GAC

IR, IN, GW

0.76f

Water Factory 21, CA

2nd

F, GAC, RO

GW

0.88

d IR, irrigation; IN, industrial; GW, ground water recharge.

e Operating costs only.

f Capital cost only.

SOURCES: Compiled from Asano, 1985; NRC, 1994; East Bay Municipal Utilities District, 1992; Filteau et al., 1995; Grebbien, 1991.

content greater than 400 mg/l or an electrical conductivity greater than 1.5 dS/m, and to the special case of potentially contaminated but otherwise potable water delivered to consumers.

The most common use of marginal quality water is of brackish water to irrigate crops that have a high tolerance for salinity. Much of the brackish ground water in the study area can be used directly for irrigation without desalination. The yields of some crops, such as strawberries or subtropical and deciduous orchards, are reduced when irrigated with water with an electrical conductivity greater than 1.5 dS/m, although the fruit may be of higher quality because of increased sugar content. Other crops, such as cotton and barley, are not affected at levels of 8 dS/m or more (Shalhevet, 1994). Management practices for using brackish water in agriculture include restricting the use of brackish water to tolerant crops and tolerant varieties, although the latter are not widely available; mixing water sources, when required, to achieve lower salinity; intermittent leaching; use of drip-irrigation technology when practicable; use of poor quality water only toward the end of the growing season; and avoiding irrigation during hot weather (Shalhevet, 1994).

Although the use of brackish water for irrigation can free up freshwater resources for other uses, this practice is not without drawbacks even with sound management practices. Assuming an irrigation efficiency of

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.11 Reclamation, Marginal Water, and Desalination

Committee Criterion

Wastewater Reclamation

Use of Water of Marginal Quality

Desalination of Brackish Water

Desalination of Seawater

1.

Impact on Available Water Supply

+

+

+

+

2.

Technically Feasible

+

+

+

+

3.

Environmental Impact

+

+/-

+

+/-

4.

Economically Feasible

+/-

+/-

+

-

5.

Implications for Intergenerational Equity

+

+/-

+

?

NOTE: + indicates positive effects, and - indicates negative effects.

75 to 80 percent, application of water with an electrical conductivity of 2.9 dS/m will result in salt accumulation in the soil to a level of approximately 4.4 dS/m in the soil saturation extract (Ayers and Westcot, 1976). Fortunately, there are a number of crops that can tolerate this level of soil salinity, among them cotton, barley, wheat, sorghum, beet, cowpea, zucchini, safflower, soybean, date palm, and many grasses. Where winter rainfall exceeds 400 mm/yr, salts accumulated during the irrigation season will be partially leached out, and salt accumulation in the soil during the following growing season will be about 3 dS/m. Under these conditions, some additional crops, such as broccoli, tomato, asparagus, and peanuts, may be irrigated directly with little likelihood of yield reduction. Leaching of salts from the soil zone, of course, results in an increase in the salinity of the underlying ground water. Use of brackish water (as well as wastewater) to irrigate fields overlying water table aquifers (such as the coastal plain and the Jordan Valley) is therefore not sustainable unless the salinity buildup is managed.

A preliminary analysis of brackish ground water in Jordan with salinity suitable for irrigation of salt-tolerant crops indicates that 70 to 90 million m3/yr may be safely withdrawn from aquifers on the eastern shore of the Dead Sea (WAJ open files). More than 300 million m3/yr of brackish water are available west of the Jordan valley (Goldberg, 1992); about 65 million m3/yr discharge to springs on the west shore of the Dead Sea within the West Bank (primarily the Feshka and Turieba Springs), about 40 million m3/yr are available in the Gaza Strip, and an additional 200 million m3/yr of brackish water is available throughout Israel.

With time, the quantity of marginal water in the area will increase because of saline water encroachment and the infiltration of pesticides,

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

fertilizers, and wastewater into freshwater aquifers. For example, the chloride content of the coastal aquifer in Israel and the Gaza Strip is increasing at the rate of about 2 mg/l of chloride per year. Eventually, the problem of water supply from the coastal aquifer will be one of quality rather than quantity. The long-term use of this aquifer and others with deteriorating quality will depend on finding suitable uses for marginal quality water.

Brackish water does not always exist where it could be used beneficially. However, it should be regarded as a valuable resource and transported to areas of use. For example, there are three separate distribution systems in the Negev Desert: the National Water Carrier, transporting freshwater; the ShafDan System, transporting treated wastewater; and a brackish water line transporting water from the Negev Plateau. Clearly, an expanded role for brackish water (as well as wastewater) will require similar engineering schemes throughout the study area.

Water supplies contaminated by inorganic and, in some cases, organic pollutants represent a special case of water of marginal quality. Contaminated water results not only from pollution of surface- and ground-water sources, but also from contamination of potable water distribution systems. In some cities, pipe distribution systems are in need of repair. The leaky pipes admit contamination when broken water mains are repaired and when water shortages depressurize the system. Water storage in homes, or on the roofs of buildings, provides breeding opportunities for harmful bacteria. It may be impractical to solve these problems by investing substantial amounts of capital into reconstructing the water distribution systems. Another possibility is to provide a final treatment for potable water just prior to its use.

Several competing technologies are in use for point-of-use (at the tap) and point-of-entry (at the house) water treatment. These range from natural coagulants (seeds of Moringa olifera and Strychnos potatorium ) (Gupta and Chaudri, 19920 to reverse osmosis membranes (Tobin, 1987). Practicality depends on the cost and reliability of the technology. An educational program is also a prerequisite, for the consumer, the manufacturer, and the local water utility.

The following specific technologies in use fall into four categories: adsorptive filters, reverse osmosis, ion exchange, and distillation (Rozelle, 1987):

  • Adsorptive filters. Adsorptive filters usually rely on granulated activated carbon (GAC). They reduce common tastes and odors, some turbidity, residual chlorine, radon, and many organic contaminants. Efficiency depends on the design. This method is probably the most cost-effective for point-of-use treatment. The carbon surfaces do provide opportunities
Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×
  • for bacterial growth under stagnant conditions, but a U.S. EPA study of 180 homes reportedly showed that the GAC filters had no significant gastrointestinal and dermatological effects (Calderon et al., 1987).
  • Reverse osmosis (RO). Reverse osmosis is the "high tech" method for reducing dissolved inorganics. It can remove some organics, depending on the type of membrane. Such units include, first, a particulate filter, followed by a GAC filter, the RO module, a water reservoir containing a pressurized rubber bladder, a final GAC filter, and a special spigot to the sink. The units operate solely on water main pressures between 40 and 70 pounds per square inch gauge (psig) (276 and 483 kilopascals [kPa]) on nonbrackish water up to 2,000 mg/l of total dissolved solids (TDS), and deliver up to 1 gpm (0.63 l/s). Removal performance depends on the type of membrane used, most commonly cellulose acetate or polymide.
  • Ion Exchange. Ion exchange has been used for many years to soften water. It also reduces barium and radium, nitrates, some arsenates, and uranium anion.
  • Distillation. Distillation is an effective method for producing contaminant-free water. Used in some water-bottling operations, the process is energy-intensive.

Maintenance is essential for these units to function properly. Particulate filters must be replaced before clogging and adsorptive media must be replaced before becoming saturated with contaminant. Replacement cycles depend on the water-use rate, the type of contaminant, and its concentration in feedwater. RO membranes typically operate for one to four years without membrane fouling or deterioration. Ion exchange units must be regenerated or replaced periodically. Distillation stills must be cleaned to avoid scaling.

Point-of-entry treatment is a major industry, supplying potable water to millions of consumers who are in isolated areas, on farms, or in communities where wells have been contaminated. The method is technically sound and economically feasible for reducing organic and inorganic contaminants. Controlling and monitoring these devices is the key to protecting public health.

Some states in the United States have established regulations that require a public utility type of organization for point-of-entry devices (Burke and Stasko, 1987). New York State has passed enabling legislation to form water districts that carry out point-of-entry treatment device programs in cases of private well contamination. Guidelines have been developed to ensure that the devices are properly installed, operated, and maintained by water districts, once the districts are organized. This program

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

is expected to ensure safe drinking water for approximately three million people at a reasonable cost.

These devices clearly have their place for isolated users, but they could be used more widely to improve the overall standard of drinking water in the study area. They are more than an alternative form of treatment—they are flexible potential components of a water supply system. Use of these devices should be considered in the context of overall water supply and water reuse systems. Specific factors to consider include the institutional structure that would provide the devices and their maintenance, the quality of the raw water source and need for pretreatment, opportunities for contamination while water is in transport to the consumer, and the nature of the decentralized industry that would stem from widespread manufacture, installation, and maintenance.

The evaluation of using waters of marginal quality is also summarized in Table 5.11. By tailoring water supplies of differing quality to appropriate uses, it may be possible to use water of impaired quality that would otherwise remain unused. In this way, the available water supply would be increased. In many instances the use of marginal quality water is technically feasible. The environmental impacts of such use depend on the type and location of use. The continued recycling of irrigation tailwaters, for example, will ultimately lead to severe soil salinization, or, where salinity is actively managed, the need to manage significant quantities of saline drainage waters. The use of water of marginal quality is likely to be feasible where the water and the use are matched, so that substantial treatment costs are avoided. Finally, the use of these waters will tend to promote sustainability, stretching existing water supplies further, thus preserving the stocks and qualities of water available now and for future generation.

Desalination of Brackish Water

According to the International Desalination Association (1996), by December 1995, there were approximately 11,066 desalting units in operation worldwide, with a total capacity of 20.3 million m3 per day (Figures 5.3 and 5.4). Considerable data have been assembled on technologies that are pertinent to the study area (e.g., Box 5.4; Awerbuch, 1988; and Hoffman, 1994). Small plants are already in operation in Israel (Glueckstern, 1991) and the Gaza Strip, and are being studied in Jordan (Fatafta et al., 1992). These plants have been used to evaluate technologies and refine cost estimates for large-scale desalination plants. The decision to introduce large-scale desalination into the study area depends on economics and on the success of other programs to manage demand or augment supplies. As long as other means of increasing the net availability

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

FIGURE 5.3 Cumulative capacity of all land-based desalting plants that can produce 100 m3 per day per unit or more of freshwater, by contract year. SOURCE: Reprinted, with permission, from Wangnick Consulting GmbH, 1996. ©1996 by Wangnick Consulting GmbH.

FIGURE 5.4 Capacity of all land-based desalting plants becoming active that can produce 100 m3 per day per unit or more of freshwater, by contract year.

SOURCE: Reprinted, with permission, from Wangnick Consulting GmbH, 1996. ©1996 by Wangnick Consulting GmbH.

of water are less expensive, they will doubtless be developed to their fullest extent before desalination plays a major role in the area's water supply. According to Fisher et al. (1996) desalination will not be cost-effective in the study area until at least 2020.

One way to reduce the net cost of desalination is to tie the desalination

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

BOX 5.4 Rural India: Brackish Water Desalination for Potable Use in Economically Developing Areas

Many arid and coastal regions of India must surmount severe water quality problems if reliable potable supplies are to be developed. These problems include high levels of salinity, nitrate concentrations, and pathogenic bacteria, in some cases, the presence of guinea worms. In the 1980s, a task force was assembled consisting of representatives from government, industry, and private organizations, to develop a potable water action plan. The resulting action plan was based on the following principles:

  • A number of small plants, rather than a few centralized plants, would be required, since villages were highly dispersed over large areas.
  • Standardized plant sizes, with capacities of 10, 20, 30, 50 or 100 m3/day were to supply villages based on a designed demand of 10 l/day per person.
  • Waters with total dissolved solids greater than 5,000 mg/l would undergo sand filtration, reverse osmosis, and disinfection.
  • Waters with total dissolved solids less than 5,000 mg/l would undergo sand filtration, electrodialysis, and disinfection.
  • Firms selected to design and construct plants would be required to (1) operate and maintain the plants for three years; (2) supply potable water to villages in the event of a plant shutdown; and (3) train local technicians to operate and maintain the plants.

Over 120 villages throughout India were selected to participate in the program. A total of 18 electrodialysis and 29 reverse osmosis plants were installed. Designs were kept as simple as possible due to the remoteness of many of the villages. Where feasible, local materials were used in construction. Standby diesel generators were installed at plants to avoid erratic power supplies in some villages, and emergency spare parts were stored at remote treatment sites. Where possible, plant brine was disposed of into nearby saline water bodies. Other disposal strategies included constructed evaporation ponds and ground-water injection.

This case illustrates how appropriately scaled technology can be employed to provide a potable water supply for communities and populations that are widely dispersed, where brackish water is readily available. The costs of the water vary with the quality of the source water and with the capacity of the treatment plant. In some instances, brine disposal may present problems, although evaporation ponds are generally effective in areas with high rates of evaporation. The success of this plan lies in appropriately scaling the technology to local conditions, use of local materials in construction, and employment of local residents to operate and maintain the plants.

process to other water projects. An example would be to substitute desalination for secondary and tertiary treatment of wastewater, so that the net cost of desalination would only be the cost above standard treatment. This approach might answer the public reluctance to accept reclaimed wastewater as a potable supply, and it may be practical if the

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

availability of wastewater exceeds irrigation demand. Desalination of wastewater would also help avoid salinity increases in soil and water. Offshore or coastal wells might also withdraw saline water for desalination. Where conditions are favorable, a line of saline water wells could create a pumping trough that would stabilize the movement of the freshwater-saltwater interface in a coastal aquifer. The protection of the freshwater aquifer would be an added benefit to the desalination process.

The lead time in evaluating brackish or saline sources of water, determining appropriate methods of brine disposal, and designing and constructing desalination plants must be considered in the overall planning. The environmental impacts of brackish or saline water extraction on the source water body and the impacts of disposal of the by-product brine on the receiving water can both be significant, particularly for large-scale projects.

Large supplies of brackish ground water exist throughout the study area, generally as part of complex ground-water flow systems, with freshwater occurring in shallow, or up-gradient, positions, and more saline water in deeper, or down-gradient, positions. The brackish water component of such flow systems cannot be developed without some long-term effect on adjacent fresh or saline components. Depending on the position of the wells in the flow system, withdrawal of brackish water results in either increased or decreased salinity. If salinity increases, the cost of desalination will generally increase; if salinity decreases, part of the adjacent freshwater resource will be depleted. Therefore, brackish water resources cannot be considered a "free good" or unlimited resource, but must be evaluated to determine their yield, salinity changes with time, and the effect of withdrawal on adjacent freshwater resources.

Another source of brackish water for desalination is agricultural return flow. Such flow constitutes the bulk of the water entering the Jordan River below Lake Kinneret/Lake Tiberias/Sea of Galilee. It has been suggested (Biswas et al., 1997, pp. 5.13-14) that drainage projects on both sides of the Jordan Valley could collect return flow that could be desalinated relatively inexpensively. Such a project would have the added benefit of rehabilitating Jordan Valley ecosystems if sufficient natural freshwater flows of desalinated water were maintained. Brackish ground water and agricultural return flows with salinities low enough for direct use as irrigation water should probably be reserved for this purpose.

Four distinct classes of technology are available for treating saline water. They are distillation technologies, electrodialysis, reverse osmosis, and salinity gradient solar ponds. With the exception of distillation, the cost of freshwater produced by each of these technologies depends on whether the raw water source is brackish water or seawater. The following

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

sections describe those technologies most appropriate for treating brackish water.

Distillation.

The oldest and best known desalination technologies are based on distillation. With these technologies, saltwater or brine is boiled, and the dissolved salts, which are not volatile, remain in solution as water is vaporized. When the evaporated water is cooled, pure water condenses. The Multi-Stage Flash (MSF) evaporation method (MSF) consists of a number of interconnected stages. Vapor pressure is maintained at each stage so that the boiling point of the feedwater is below its incoming temperature. Flashing occurs in steps as the feedwater passes in series through stages at successively lower pressures. The advantage of this system is that it can be operated at relatively low temperatures (70°C). A second distillation method, called the Multiple Effect (ME) evaporation system, uses evaporator chambers (the effects) that receive heat from an external source. The evaporation feed is preheated by hot product water from each effect. The process reuses heat very efficiently.

Distillation technologies are energy-intensive and the costs of producing product water are sensitive to energy costs. However, the costs do not vary with the quality of the feedwater and thus costs of desalting brackish water are approximately the same as for desalting seawater. Two technologies, electrodialysis and reverse osmosis, provide less costly means of desalting brackish waters.

Electrodialysis.

The electrodialysis (ED) method of desalination is based on selective movement of ions in solution and the use of semipermeable membranes. When a current is applied, positive ions (cations) migrate to the negative pole, and negative ions (anions) migrate to the positive pole. A cation-permeable membrane allows cations to pass, but blocks anions. An anion-permeable membrane allows anions to pass, but blocks cations. Sets of the two types of membranes create alternate salt-depleted (product) and salt-enriched (brine) solution streams. Electrodialysis tends to be an attractive technology for desalting water with TDS concentrations of 3,000 mg/l or less, because its energy use in this range compares favorably with other technologies. Table 5.12 summarizes operating experience with electrodialysis units to desalt brackish waters in the United States and Canada. The data indicate that electrodialysis production costs are relatively high when compared to the costs of wastewater reclamation. Costs tend to be sensitive to the quality of the source water, although plant scale and specific type of technology used are also important.

Reverse Osmosis.

The reverse osmosis process employs hydraulic pressure

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.12 Costs of Brackish Water Desalination with Electrodialysis

Plant Location

Date On Line

Feed TDS (mg/l)

Capacity (m3/day)

Unit Cost ($/m3)

Yuma Proving Grounds AZ

1986

1,800

760

3.12

Granbury Water Treatment Plant TX

1985

1,625

490

2.33

Brazos Reservoir Authority TX

1989

321

10,980

1.24

Melville Water Treatment Plant Canada

1990

1,900

1,890

0.88

Foss Reservoir OK

1974

1,000

5,300

0.58

Robert House Reservoir VA

1990

7,570

690

0.50

NOTE: All costs in 1996 dollars. Total dissolved solids (TDS) of product water is less than 600 mg/l. Operating and maintenance costs normalized assuming an electricity cost of $0.04/kWh. Unit costs computed using a 20-year amortization period for capital costs and a 10 percent interest rate.

SOURCE: Reprinted, with permission, from National Water Supply Improvement Association, 1992. ©1992 by American Desalting Association.

to force pure water from saline feedwater through a semipermeable membrane (Box 5.5). The evidence suggests that reverse osmosis systems are most attractive for feedwaters with concentrations of total dissolved solids of between 3,000 and 40,000 mg/l. In this range, the reverse osmosis process uses somewhat less energy than electrodialysis. When total dissolved solids exceed 35,000 to 40,000 mg/l, multistage flash distillation becomes competitive in terms of energy use (Heitmann, 1990). Table 5.13 illustrates the costs and capacities of reverse osmosis facilities currently used to desalt brackish waters in the United States. In general, these costs vary with the scale of the plant and the technology used. The costs of facilities using relatively modern reverse osmosis technologies range from about $0.28 to $1.00 per cubic meter. The costs for desalting brackish water with reverse osmosis compare favorably with electrodialysis and with wastewater reclamation where reclamation requires extensive treatment. Generally, the costs of brackish water desalination also compare favorably with the costs of seawater desalination.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

As summarized in Table 5.12, brackish water desalination may offer an attractive alternative to augment the water supplies of the region. Such desalination is technologically feasible and usually will not have adverse environmental impacts. Economic feasibility will depend on the quality of the feedwaters, the technology used, and the relative economic attractiveness of other alternatives. By stretching the existing water supply and providing qualitative improvements, brackish water desalination is likely to produce relatively favorable consequences for present and future generations.

Seawater Desalination

Seawater conversion tends to be very expensive, with costs ranging upward from approximately $1.00/m3. The costs of seawater desalination are significant, by setting an upper bound on the costs of additional water supplies for the Middle East and other areas with access to the sea. As far as we know, seawater desalination has the potential to provide virtually all the additional water needed in the study area, with possible negative environmental impacts limited to the effect of brine disposal on the receiving water. However, note that the seawater desalting costs reported here are for water at the desalting plant boundary. The costs of transport and pumping facilities must be added, along with the costs of operating and maintaining these facilities. Because desalting facilities will always be located at sea level, pumping costs can be especially significant, and seawater desalination will be most cost-effective in areas adjacent to the coast. The most cost-effective inland benefits of seawater desalination are likely to be the substitution of desalted water for freshwater supplies that will then be available for reallocation to other uses and other places. The comparative cost data suggest that, where wastewater is available for reclamation or significant supplies of brackish waters are available, it will generally be less costly to treat and reclaim these waters than to invest in seawater desalination.

Distillation

The traditional distillation technologies (discussed above) have costs that are extremely sensitive to energy prices, and, as a result, are only employed on any significant scale where there is no alternative source of water and energy is relatively plentiful.

Reverse Osmosis

In the last decade, reverse osmosis technology has been adapted for

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

BOX 5.5 Desalting Brackish Ground Water in Southern California

Continued population growth in southern California is placing intensified pressures on the region's water supplies. Nearly 75 percent of the water supplies available to southern California are imported. The prospects of developing additional sources of imported supply to serve population growth are uncertain. Competition for water to serve environmental purposes is intense, and the costs of additional imported supplies will be very high, probably $0.60/m3, and in many locales significantly higher. A number of local water purveyors in the southern California area have turned to brackish ground water as an alternative source of supply. The costs of reclaiming brackish ground water using reverse osmosis fall in the range of $0.28 to $0.45/m3, and thus compare quite favorably with the costs of new imported supplies. Three existing projects and one proposed project illustrate the variation in source water quality and uses.

Arlington Basin Desalting Project

The Arlington Ground Water Basin, approximately 80 km east of central Los Angeles, contains over 370 million m3 of ground water that has been degraded with the residues of agricultural chemicals applied in the area over the past 70 years. Although the level of total dissolved solids (TDS) is only 1,100 mg/l, concentrations of nitrate-nitrogen exceed the existing standard, and dissolved organic residues of pesticides and herbicides are also present. In 1990, a pump-and-treat system employing reverse osmosis and activated carbon was placed in operation. The project produces potable water at a rate of 22,700 m3/day. The water is blended and consists of two-thirds reverse osmosis permeate and one-third water treated with activated carbon. The unit cost is $0.28 m3, which compares very favorably with the costs of alternative sources of potable water.

West Basin Desalter Project

Historically, the West Ground Water Basin, which is located immediately south and west of the city of Los Angeles, was subjected to heavy overdraft, resulting in seawater intrusion. In the early 1960s, the local water agency, the West Basin Municipal Water District, began to inject good quality water into the basin to act as a seawater intrusion barrier. Although this project succeeded in halting the seawater intrusion, some saline water was trapped inland of the barrier. This saline water continues to degrade ground-water quality, which has TDS of 4,000 mg/l. In 1993 the West Basin district began operating a reverse osmosis facility to reclaim the saline ground waters trapped inland of the seawater intrusion barrier. The facility has a capacity of 5,500

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

m3/day and produces potable water supply for the city of Torrance at a cost of $0.42/m3.

San Luis Rey Basin Desalting Facility

The city of Oceanside, California, which is located midway between Los Angeles and San Diego, depends on a regional water purveyor for domestic water supplies. The need for extensive conveyance facilities to transport this water makes the system vulnerable to a catastrophic earthquake. The system is also vulnerable to extreme drought. The city has no alternative supply of water, and its storage capacity holds only enough supply to meet municipal demands for two days. The San Luis Rey Ground Water Basin, which is adjacent to Oceanside, is salinized, with TDS measuring approximately 1,400 mg/l. In 1994, Oceanside began operation of a 5,570 m3/day reverse osmosis facility, which desalinates the ground water for potable use. The facility produces water at a reported cost of $0.31/m3, less than half the cost of a supplemental imported water supply. Product water contains less than 10 mg/l TDS and meets all water quality standards for potable water. The project provides the city with additional water supply and substantial protection against drought or a failure in its conveyance system.

Frances Desalting Facility

Orange County, which lies at the southern margin of the Los Angeles metropolitan area, has historically been short of water and has developed a number of innovative means of augmenting water supplies. One of the local water purveyors, the Irvine Ranch Water District, already provides potable and recycled water to domestic customers through separate plumbing systems, which were installed as part of the planned development of a number of the communities that it serves. The area serviced by the Irvine district continues to grow, and additional sources of water are needed. The underlying ground water is slightly brackish, with a TDS of 870 mg/l. The district has studied various technologies for reclaiming this water, including nanofiltration, electrodialysis, reverse osmosis, and ion exchange. Reverse osmosis was found to be the most cost-effective. The district now proposes to construct a 37,100 m3/day reverse osmosis ground-water desalting facility. This facility would produce potable water for use within the district's service area and would be the largest ground-water desalination facility in the United States. The cost of the water is estimated to fall in the range of $0.41 to $0.47/m3. Costs in this range would be substantially less than the costs of alternative sources of potable water.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.13 Costs of Brackish Water Desalination with Reverse Osmosis

Plant Location

Date On Line

Capacity (m3/day)

Unit Cost ($/m3)

Water Factory 21, CA

1977

18,670

0.28

Oceanside, CA

1994

7,570

0.43

Arlington Desalter, CA

1990

15,140

0.48

Cape Coral, FL

1976

28,250

0.48

Brighton, CO

1993

10,590

0.50

S.E. Region Water Treatment Facility, IL

1989

5,130

0.62

Sarasota, FL

1982

11,410

0.83

Gasparilla Islands, FL

1990

1,200

0.91

Dare County, NC

1989

5,920

1.05

North Beach, FL

1985

1,140

1.06

Jupiter, FL

1990

7,780

1.09

St. Thomas Dairies, Virgin Islands

1980

57

2.61

Southbay Utilities, FL

1980

472

2.99

Okracoke Sanitary District, NC

1977

395

3.67

NOTE: All costs in 1996 dollars. Total dissolved solids (TDS) of feedwaters are between 1,000 and 5,000 mg/1. TDS of product waters ranges from 25 to 400 mg/1. Operating and maintenance costs are normalized using an electricity cost of $0.04/kWh. Unit costs computed using a 20 year amortization period for capital costs and a 10 percent interest rate.

SOURCES: Compiled from Cevaal et al., 1995; Kopko et al., 1995; National Water Supply Improvement Association, 1992; and Szymborski, 1995.

seawater desalination with costs that are relatively attractive compared to distillation technologies. Table 5.14 shows cost and capacity data for a selected set of seawater conversion projects employing reverse osmosis technologies around the world. With the exception of Santa Catalina Island, CA, where the high cost is particularly attributable to small plant size and the absence of economies of scale, costs range from approximately $0.90/m3 to $1.35/m3. Thus, although seawater desalting with reverse osmosis may be less costly than distillation technologies, it is still quite expensive.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

TABLE 5.14 Costs of Seawater Desalination with Reverse Osmosis

Plant Location

Date On Line

Capacity (m3/day)

Unit Cost ($/m3)

Santa Catalina Island, CAa

1991

380

3.17

Tigne, Maltab

1987

15,140

0.92

Las Palmos, Gran Canariab

1989

35,958

1.35

Rosarita Repowering Project, Mexicoc

Proposed

37,851

1.24

Jedda I, Phase 1, Saudi Arabiab

1989

56,777

0.95

NOTE: All costs are in 1996 dollars. Source water ranges from 36,000 to 47,000 mg/l total dissolved solids. Total dissolved solids for product water are less than 500 mg/l. Operating and maintenance costs are normalized using an electricity cost of $0.04/kWh. Unit costs computed using a 20-year amortization period for capital costs and a 10 percent interest rate.

a Modified from National Water Supply Improvement Association, 1992.

b Modified from Leitner, 1991.

c Modified from Kamal, 1995.

Salinity-Gradient Solar Ponds

A number of researchers have proposed salinity-gradient solar ponds as an alternative means of desalinating seawater. The theoretical advantage of this technology lies in the fact that energy generated from the salinity gradients can be used to power either the desalting process or the desalination facilities.

The pond is maintained with a salinity gradient that increases with depth, with a low-salinity, low-density surface zone floating on top of a high-salinity, high-density lower zone. Between these two layers is a gradient zone of intermediate salinity that acts to isolate the surface and lower zones. The lower zone traps solar energy in the form of heated water. The high density of the lower zone (caused by high salinity) inhibits the heated water from rising, thereby minimizing heat loss to the atmosphere. Lower zone water temperatures can exceed 80°C.

The heat trapped in the lower zone can be used directly to warm saline water for distillation, or indirectly to generate electricity to run desalination facilities. Many researchers have proposed the coupling of salinity-gradient ponds with distillation at temperatures of approximately 70°C and thus the feedwater to a distillation unit could be heated with water from the lower zone of a solar pond. The advantages of the system

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

may include low energy use and low pollution production. Such a technology would be especially suitable for remote arid environments with limited local energy sources. Solar ponds could also be used to generate electricity to operate reverse osmosis desalination plants. However, there are large inefficiencies inherent in producing electricity, compared with directly using water heated in ponds.

Currently, there are no large-scale desalination facilities using salinity-gradient solar ponds. However, a number of pilot studies have been conducted, and some ponds are being used to generate electricity. Since the early 1980s, Israel has operated several salinity-gradient solar ponds for energy production. A pond in Ein Boqek was the first to generate commercial electricity, producing a peak output of 150 kW. Ponds with a total surface area of 250,000 m2 in Beit Ha'Arava are the heat source for a 5 MW power station. Cost data for proposed solar-pond multieffect distillation facilities are shown in Table 5.15. These data suggest that seawater desalting with solar ponds may sometimes be competitive where the costs of energy are relatively high or energy availability is constrained. The costs do not differ substantially from those of reverse osmosis seawater desalination, whose energy costs are in the range of $0.04 to $0.08/kWh.

The evaluation of seawater desalination is summarized in Table 5.11. Clearly, large-scale seawater desalination could substantially add to the available water supplies of the study area. Seawater conversion using either distillation or membrane technologies is feasible. The environmental impact of seawater conversion mainly relates to the disposition of the concentrated brines resulting from any seawater conversion operation. The method and place of disposal will be important in determining the environmental impact. To date, seawater desalination has only been economically feasible in unique situations where water supplies are intensively constrained. The adverse economics of seawater conversion are

TABLE 5.15 Reported Cost of Seawater Desalination Using Solar Ponds and Distillation Technologies

Reference

Pond Size (1,000 m2)

Production (m3 / day)

Reported Unit Cost ($ / m3)

Dornon, et al. (1991)

600

9,000

1.13

Glueckstern (1995)

1,200

20,000

0.89

Glueckstern (1995)

12,000

200,000

0.71

Tsilingiris (1995)

35,000

100,000

2.00

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

likely to persist for the immediate future. The implications for future generations of employing seawater conversion on a large scale are not clear. Certainly, the development of a cost-effective technology that could be passed on would be a positive contribution to future generations. Nevertheless, uncertainties about the economic feasibility of these technologies and their environmental impacts make it difficult to assess their implications for present and future generations.

Cloud Seeding

For many years, people have tried to modify weather to increase water resources. The discovery in the late 1940s that supercooled cloud droplets could be changed to ice crystals by inserting a cooling agent such as dry ice or artificial nuclei such as silver iodide led to cloud seeding to increase precipitation. While cloud seeding has been used in the study area since 1960, its effects on precipitation are still controversial. Moreover, increases in precipitation do not necessarily result in more runoff, which is critical to water supply. The initial optimism about these techniques has been somewhat tempered by the complexities of atmospheric physics (Bruintjes et al., 1992).

From 1961 to 1975, two scientifically designed cloud-seeding experiments were carried out in north and central Israel using a two-target crossover design. The first experiment claimed a positive seeding effect of 15 percent increase in rainfall and the second a positive effect of 13 percent increase in rainfall in the northern part of Israel; the results of both studies were statistically significant at relatively high levels (Nirel and Rosenfeld, 1995). Since 1975, cloud seeding has been used in the north. Increased rainfall from cloud seeding between 1976 and 1990 is estimated at 6 percent, with a 95 percent confidence level (Nirel and Rosenfeld, 1995). The Jordan cloud-seeding program is estimated to have increased rainfall by 19 percent (Tahboub, 1992). Even where the strategy was apparently successful, however, increases in runoff were less significant than increases in precipitation (Benjamini and Harpaz, 1986).

Cloud seeding in the south of Israel has remained experimental. Analyses have not indicated any rainfall increase (Rosenfeld and Farbstein, 1992; Brown et al., 1996). This result may be due to desert dust, possibly from the Sahara-Arabian deserts, which contributes many nuclei and may reduce seeding's effects (Rosenfeld and Farbstein, 1992; Gabriel and Rosenfeld, 1990).

Recent statistical analysis by Rangno and Hobbs (1995) suggests that the cloud-seeding experiments have been compromised by statistical errors, and that neither of the two Israeli experiments demonstrated statistically significant effects on rainfall from cloud seeding. In some circumstances,

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

cloud-seeding methods have been suspected of decreasing precipitation (Rosenfeld et al., 1996). The 1992 World Meteorological Organization Statement on the Status of Weather Modification concluded that ''if one were able to precisely predict the precipitation from a cloud system, it would be a simple matter to detect the effect of artificial cloud seeding on that system. The expected effects of seeding are, however, often within the range of natural variability … and our ability to predict the natural behavior is still limited" (WMO, 1992).

Since the beginning of the endeavor, there has been international concern about the social and ecological effects of cloud-seeding operations and the economic costs and benefits of the technology (Fleagle et al., 1974). Concerns have also been raised about potential effects on precipitation in downwind countries (WMO, 1992). In 1979, the World Meteorological Organization and the United Nations Environment Program considered draft general guidelines for states concerning weather modification, but they were never finalized (WMO/UNEP, 1979). The guidelines called for notice and consultation with potentially affected countries and for assessments of environmental effects (a point reiterated in the 1992 WMO Statement on Weather Modification). In the 1960s and 1970s, more than a dozen lawsuits were filed in the United States (Brown Weiss, 1983). Further research is still needed to clarify the effects of cloud seeding on precipitation. At this time, it is doubtful that cloud seeding will ever provide a significant source of increased water supply in the study area. Regional cooperation is important to ensure that all countries appreciate the scientific uncertainties about the technology and its impacts. Monitoring for possible effects outside the target area is also important.

Table 5.16 summarizes the evaluation of cloud seeding based on the committee's five criteria. As noted earlier, the effects of cloud seeding on the availability of water in the study area are not completely clear, and it is unlikely that cloud seeding would ever provide a significant source of

TABLE 5.16 Cloud Seeding and Transfers

Committee Criterion

Cloud Seeding

Transfers

1.

Impact on Available Water Supply

0–?

0

2.

Technically Feasible

+

+/-

3.

Environmental Impact

–?

+/-

4.

Economically Feasible

?

+/-

5.

Implications for Intergenerational Equity

 

?

NOTE: + indicates positive effects, – indicates negative effects, and 0 indicates no impact.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

additional water supply. Moreover, very little is known about its technical or economic feasibility or its environmental impact. The implications of cloud seeding for present and future generations are similarly unclear.

Transfers Within the Study Area

Water transfers are used to shift water surpluses generated in one part of the system to another part in need of additional water supplies. There are extensive transfers of water from one area to another within the study region. More transfers are under consideration for the future. In Israel, the National Water Carrier transports an average of 450 million m3/yr from the north to the south of the country using the Lake Kinneret/Lake Tiberias/Sea of Galilee as a storage reservoir. In Jordan, the King Abdullah Canal, with a capacity in the northern reaches of 600 million m3/yr, decreasing to 180 million m3/yr in the southern part of the valley, and an average flow of 140 to 160 million m3/yr, diverts water from the Yarmouk River and provides water to irrigate the upper Jordan Valley. The canal also provides the water for the Deir Alla project (consisting of a pipeline, treatment plant, and pumping plants), which provides an average of 35 million m3/yr to Amman.

The transfer of seawater to the study area has been proposed many times. It would be complex and expensive. The proposed Dead Sea projects would bring saline water from the Mediterranean Sea or Red Sea to the Dead Sea by means of pipelines or canals. The transferred seawater would reverse the trend of falling water levels in the Dead Sea, eventually restoring and maintaining its historic levels; hydroelectric generating stations would take advantage of the elevation difference between the Dead Sea and sea level; and the elevation drop could also furnish the mechanical pressure needed for reverse osmosis desalination, therefore minimizing the use of electricity. The cost-effectiveness of these projects needs to be evaluated based on their total packages of benefits—freshwater production, environmental restoration, continuation of chemical production from the Dead Sea, and power generation.

Transfers of water within the area will not result in any net increase in the available water supply, since they simply reallocate water among uses and places of use. Some transfers will be technically feasible, where facilities exist to move water from one place to another. Other transfers may not be technically feasible, because the physical means to accomplish the transfer are absent. Similarly, the environmental impact of transfers is unclear. Where water is transferred from consumptive uses to environmental uses, the environmental impact is likely to be positive.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

Imports of Freshwater into the Study Area

Proposed approaches to import freshwater from outside the region would be complex and expensive, and would require international agreements. They would generally involve moving freshwater by conventional pipelines and canals from other countries such as Turkey (Biswas et al., 1997), or in one instance, transporting the water in large floating plastic bags pulled by tugboats (Tahal Consulting Engineers, 1989). The committee did not evaluate such proposals, because they are outside the scope of this study. Moreover, there is danger that serious consideration of import schemes may prevent the parties in the study area from focusing on the measures that can be taken (such as those described in this study) to provide sustainable water supplies using the region's resources.

Conclusions

The conventional freshwater sources currently available in the region are barely sufficient to maintain its quality of life and economy. For example, Jordan is currently overexploiting its ground-water resources by about 300 million m3/yr, thus lowering water levels and creating salinization of freshwater aquifers. Similar examples of overexploitation are occurring throughout the study area. Attempting to meet future regional demands by simply increasing withdrawals of surface and ground water will result in further unsustainable development, characterized by widespread environmental degradation and depletion of freshwater resources. Because these conditions already exist in many parts of the area, for example the Azraq Basin and the Hula Valley, the reality of a constrained water supply is a consideration in formulating government economic plans and policies. Demand and supply can be brought into a sustainable balance only by changing and moderating the pattern of demand by introducing new sources of supply. Above all, water losses should be minimized and water-use efficiency increased substantially. The opportunities offered by specific options to increase and sustain the quantity and quality of the region's freshwater resources are summarized immediately below. Each option deserves careful consideration in terms of practical application and refinement through further research. These options can be initiated in the region within existing legal entitlements to shared water resources.

Conservation

Constraints must be imposed to conserve and limit the use of available water in the study area. By reducing the demand for water, the

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

recommended conservation measures will have a positive effect on water quality and the environment. Voluntary domestic water conservation measures include the following:

  • Limiting toilet flushing.
  • Adopting water-saving plumbing fixtures, such as toilets and shower heads.
  • Adopting water-efficient appliances (notably washing machines).
  • Limiting outdoor uses of water, as by watering lawns and gardens during the evening and early morning, and washing cars on lawns and without using a hose.
  • Adopting water-saving practices in commerce, such as providing water on request only in restaurants and encouraging multiday use of towels and linens in hotels.
  • Repairing household leaks.
  • Limiting use of garbage disposal units.

Examples of involuntary domestic water saving measures include the following:

  • Repair leaking distribution systems.
  • Repair leaking sewer pipes.
  • Expand central sewage systems.
  • Meter all water connections.
  • Ration and restrict water use.

In conclusion, various known methods can lead to significant savings in both indoor and outdoor water use. To implement these methods, government agencies in the study area should consider encouraging their adoption through education, incentives, pricing, taxation, and regulation, and to this end will be involved in setting priorities at various times for the support of needed measures, taking into account the uncertainties attached to the available evidence.

Agriculture

Through rationing, research, and possibly economic pricing policies, agricultural water use can become more efficient. However, as regional nonagricultural water demand increases and the cost of additional water supplies grows more expensive, the role of agriculture in the area's economy will have to be reevaluated, so that as much water as possible is conserved. The region might adopt agricultural practices more in harmony with the ecological realities of drylands. Drylands are and will

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×

likely remain marginal for subsistence agriculture, unless the practice is heavily subsidized by water drawn from elsewhere.

A number of useful practices are already used to some degree in the study area, and these practices should be expanded to help conserve agricultural water use:

  • Harvesting local water runoff and floodwater to increase water supplies for dryland agriculture.
  • Reducing evaporative water loss by cropping within closed environments (desert greenhouses). This method is economic with land and water use, avoids soil salinization, and produces high yields of exportable crops, such as ornamentals, fruits, vegetables, and herbs.
  • Using computer-controlled drip "fertigation" (fertilizer applied with irrigation water) and soilless substrates in greenhouses, which economizes on water and fertilizer use and helps prevent ground-water pollution.
  • Considering the use of brackish water for irrigation of salinity-tolerant crops.
  • Saving more freshwater by switching to irrigation with treated wastewater or with brackish water if possible.
  • Changing production from crops with high water requirements to crops with lower water requirements.

Pricing and Pricing Policies

Policies that subsidize the price of water or emphasize revenue recovery to the exclusion of economic efficiency are poorly suited to areas where water is scarce. Conversely, pricing policies that promote economic efficiency and economizing in water use are more appropriate for regions of increasing water scarcity.

Marginal Cost Pricing

The committee recommends the use of marginal cost pricing in the study area to help conserve freshwater resources. As long as marginal costs are higher than average costs, the use of marginal cost pricing will ensure that revenue requirements are met. Marginal cost pricing also sends the correct signals to consumers about the true cost of water and, given some fixed level of benefits, ensures that the costs of providing the water are minimized.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×
Time-of-Use Pricing

Time-of-use structure discourages use of water during peak-use periods in order to ration water during high use but specifies lower pricing during off-peak usage.

Water Surcharges

Water surcharges, imposed beyond some set level of use, can be employed to discourage excessive use.

Water Markets

Water markets, where marginal cost prices are used, can help allocate water among sectors more efficiently. Markets permit transfers of water to occur on a strictly voluntary basis. Such transfers occur when the difference between the minimum price that sellers are willing to accept and the maximum price that buyers are willing to pay is sufficient to cover any costs of transport or treatment.

Even if water markets are never developed in the study area, simulation of water markets can be very useful in identifying the value of water for alternative uses and regions. Such simulation can also help identify additional water supply and conveyance facilities that are economically justified.

Watershed Management

The concept of total watershed management should be adopted for the study area. This approach has been defined as the art and science of managing the land, vegetation, and water resources of a drainage basin, to control the quality, quantity, and timing of water, toward enhancing and preserving human welfare and nature.

Small Retention Structures and Stormwater Runoff

Small retention structures on the wadis could be effective in capturing stormwater runoff. Stormwater could then be used for artificial recharge of ground water. Urban runoff is another source of water for retention basins. In addition to storing usable water, retention basins would attenuate flooding and avoid excess flows at wastewater treatment plants.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×
Ground-Water Overdraft

Ground-water mining of an aquifer that is hydraulically connected to a saline water body will deplete the freshwater resource and degrade its quality. An example is the coastal aquifer in Israel and the Gaza Strip, where overexploitation has led to the encroachment of saline water.

Because of the almost immediate environmental consequences of mining aquifers and the later environmental and water quality consequences as well, strong consideration should be given to reducing extraction rates from aquifers in the study area.

To ensure that future generations have sufficient available ground water, research is needed on the amount of water in ground-water storage and the environmental consequences of depleting this storage. In addition, more consideration should be given to the beneficial use of the storage space created by ground-water mining.

Water Harvesting

The region's inhabitants can continue and expand the use of rooftop cisterns for individual domestic supplies. Catchment systems and storage ponds should also be expanded for agricultural water use. Even where conventional sources of water are available, cisterns can provide supplemental water inexpensively and relieve the demand on the water distribution system.

Brackish Water Desalination

Where brackish waters can be desalted, this approach offers a clear promise of augmenting the available water supply. Such desalination is technologically feasible and will not usually have adverse environmental impacts. Economic feasibility depends on the quality of the feedwater, the technology used, and the relative attractiveness of other alternatives.

Underground Dams

On a small scale and under suitable physical conditions, groundwater drainage may be decreased and water levels increased by constructing underground dams. Injection of cement or low-permeability grout through closely spaced boreholes creates a curtain extending to the base of the aquifer. This approach can help prevent lateral salt water intrusion to coastal aquifers.

Suggested Citation:"5 Options for the Future: Balancing Water Demand and Water Resources." National Academy of Sciences. 1999. Water for the Future: The West Bank and Gaza Strip, Israel, and Jordan. Washington, DC: The National Academies Press. doi: 10.17226/6031.
×
Wastewater Reclamation

As the demand for water continues to increase beyond the natural supply, it is not unreasonable to forecast a near-total reuse of water in the study area. Reclamation will theoretically double the amount of increased supply brought about by new sources of freshwater as well. Thus, widespread reclamation would decrease the amounts of water needed to meet the probably increased regional demand.

Urban reuse of wastewater requires dual municipal distribution systems—one for potable, the other for reclaimed water. The prospect of major urban expansion in the area provides the incentive to plan communities with an initial dual-water system.

Marginal Quality Water Use

Some savings in freshwater could be obtained by substituting water of marginal quality for some activities now using potable water. But special attention would need to be given to any human health issues when this strategy is under consideration.

Point-of-Use and Point-of-Entry Technologies

Several competing technologies are now available for point-of-use (at the tap) and point-of-entry (at the house) water treatment. These technologies include adsorptive filters, reverse osmosis, ion exchange, and distillation.

Maintenance is essential for these units to function properly. Point-of-entry treatment is a major industry in many countries, supplying potable water to millions of consumers in isolated areas, on farms, and in communities where wells have been contaminated. The method is technically sound and economically feasible for reducing organic and inorganic contaminants. Controlling and monitoring these devices is the key to protecting public health.

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Next: Appendix A: Excerpts from the Treaty of Peace Between the State of Israel and the Hashemite Kingdom of Jordan »
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This book is the result of a joint research effort led by the U.S. National Academy of Sciences and involving the Royal Scientific Society of Jordan, the Israel Academy of Sciences and Humanities, and the Palestine Health Council. It discusses opportunities for enhancement of water supplies and avoidance of overexploitation of water resources in the Middle East. Based on the concept that ecosystem goods and services are essential to maintaining water quality and quantity, the book emphasizes conservation, improved use of current technologies, and water management approaches that are compatible with environmental quality.

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