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--> 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
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--> 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.
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--> 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$1 = 3.6 New Israeli Shekels [NIS] as of March 1998). With the full use of water-saving devices, monthly use for five people would likely be between 16 and 19.5 m3, a
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--> TABLE 5.1 Comparison of Conventional and Nonconventional Appliances in Domestic Water Use Item Conventional (1/unit) Improved (1/unit) Use Frequency (times/time/steps) Savings with Improved Technology (m3/unit) Savings/Month (m3) Values (US$) 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.
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--> 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
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--> 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.
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--> 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.
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--> 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.
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--> 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
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--> 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
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--> 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: Small farm ponds of 1,000 to 5,000 m3 each were constructed to make water supply more dependable. The traditional gravity irrigation method was replaced by drip irrigation, including peripheral equipment such as plastic supply lines, fittings, and values. 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
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--> 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
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--> 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
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--> 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.
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--> 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.
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--> 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.
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--> 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. References Abu Mayleh, Y. 1991. Hydrological Situation in Gaza Strip. Not published. Abu Safieh, Y. 1991. Water in the Gaza Strip, The problem and suggestions. In pp. 48-59 of the Proceedings of the Workshop Concerning the Water Situation in the Occupied Territories. Jerusalem, Israel: Hydrology Group. Al-Kharabsheh, A., R. Al-Weshah, and M. Shatanawi. 1997. Artificial groundwater recharge in the Azraq Basin (Jordan). Dirasat, Agricultural Sciences 24(3)September. Al-Khodari, R. 1991. The water problem in the Gaza Strip and proposed solutions. In pp. 60-65 of the Proceedings of the Workshop Concerning the Water Situation in the Occupied Territories. Jerusalem, Israel: Hydrology Group.
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Representative terms from entire chapter: