4
Prospects for Conserving and Extending Water Supplies

The history of western U.S. water development has been one in which storage reservoirs and related conveyance facilities were constructed to provide water supplies to cope with occasional drought, as well as to encourage population growth and economic development. This strategy has been complemented by a variety of means for increasing supplies and better managing demands: groundwater supplies have been tapped, irrigation practices have been refined and improved, some states and cities have adjusted landscaping practices, and there have been efforts at weather modification. More recently, both technical and legal aspects of groundwater storage methods have become more sophisticated and increasingly applied. As described in Chapter 2, the strategy of building additional surface water storage capacity is encountering physical, economic, and political limits. As more traditional water projects have become less viable, and as water demands continue to grow, federal, state, and municipal water managers across the West are considering a new water project prototype that entails nonstructural measures such water conservation, water use technologies, xerophytic landscaping, groundwater storage, and changes in water pricing policies. This chapter reviews a variety of techniques and initiatives that have been and are being explored as means to augment and extend water supplies across the Colorado River basin.



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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability 4 Prospects for Conserving and Extending Water Supplies The history of western U.S. water development has been one in which storage reservoirs and related conveyance facilities were constructed to provide water supplies to cope with occasional drought, as well as to encourage population growth and economic development. This strategy has been complemented by a variety of means for increasing supplies and better managing demands: groundwater supplies have been tapped, irrigation practices have been refined and improved, some states and cities have adjusted landscaping practices, and there have been efforts at weather modification. More recently, both technical and legal aspects of groundwater storage methods have become more sophisticated and increasingly applied. As described in Chapter 2, the strategy of building additional surface water storage capacity is encountering physical, economic, and political limits. As more traditional water projects have become less viable, and as water demands continue to grow, federal, state, and municipal water managers across the West are considering a new water project prototype that entails nonstructural measures such water conservation, water use technologies, xerophytic landscaping, groundwater storage, and changes in water pricing policies. This chapter reviews a variety of techniques and initiatives that have been and are being explored as means to augment and extend water supplies across the Colorado River basin.

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability LARGE-SCALE RESERVOIRS AND INTER-BASIN TRANSFERS Between the 1930s and the 1970s, many multipurpose dams and reservoirs were constructed in the Colorado River basin in an effort to smooth natural variations in the river’s flows and to store flood waters for use during drier periods. The prototype of these structures was Hoover Dam. The Colorado River Storage Project (CRSP) of 1956 represented another water development milestone as it authorized construction of Glen Canyon Dam (in Arizona near the Utah border), Flaming Gorge Dam (on the Green River in Utah near the Wyoming border), Navajo Dam (on the San Juan River in New Mexico near the Colorado border) and the multidam Wayne N. Aspinall Storage Unit (on the Gunnison River in western Colorado; see http://www.usbr.gov/dataweb/html/crsp.html). The CRSP represented the zenith of large-scale dam construction across the basin. Following the 1956 passage of CRSP and the construction of its authorized projects, new factors in the planning of western water resources began reducing the prospects for new projects. A burgeoning environmental movement in the post-World War II era raised awareness of environmental changes wrought by dams, leading in part to the defeat of proposals to build dams at Echo Park in Dinosaur National Monument (in the 1950s) and at Bridge and Marble Canyon near Grand Canyon National Park in the 1960s (Nash, 1967; Reisner, 1986). The trend toward fewer traditional, structural western water projects continues today, as the best sites for storage reservoirs have been developed and as concerns have grown over environmental impacts of large dams, both in the Colorado basin and elsewhere (see WCD, 2000). Some water storage and delivery projects were completed in the 1980s and 1990s, perhaps most notably the Central Arizona Project in 1992, but the declining trend of the viability of traditional water projects has been clear. In addition to environmental and other concerns related to large dams, traditional water projects today face a more stringent series of planning and feasibility studies and other obligations than in the past, which can entail literally decades of project planning and related activities. (Box 4-1 discusses the Animas-La Plata project in south-western Colorado, which is an example of the complexities that surround contemporary dam authorization, appropriation, and construction.) In efforts to augment water supplies, some basin states and

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability BOX 4-1 The Animas-La Plata Project Congress authorized the Animas-La Plata project in 1968, calling for a multipurpose dam project to serve a range of agricultural, municipal, and industrial uses in southwestern Colorado. Today, 37 years after project authorization, the Bureau of Reclamation’s Animas-La Plata project is under construction. Although scheduled for construction in the early 1980s, discussions were initiated to achieve a negotiated settlement of water rights claims of the Southern Ute Indian and Mountain Ute tribes in southwestern Colorado. Following negotiations, a settlement of water rights claims held by these tribes was agreed to in a Final Settlement Agreement, signed on December 10, 1986. In 1990, the U.S. Fish and Wildlife Service issued a draft biological opinion regarding the federally endangered Colorado pike minnow and how it might be affected by Animas-La Plata. A final biological opinion was issued in 1991, which allowed for construction of several Animas-La Plata project features, but limited annual project depletions to 57,100 acre-feet while an endangered fish recovery program was conducted. After the U.S. Bureau of Reclamation was authorized to initiate construction, several challenges were made to the completeness of Reclamation’s 1980 final environmental impact statement, and in 1992 legal actions brought by environmental organizations halted construction. Reclamation worked with the Fish and Wildlife Service to address new biological information, and in 1996 the Service issued a biological opinion with a reasonable and prudent alternative limiting project construction to features that would initially result in an average annual water depletion of 57,100 acre-feet. Construction of the Ridges Basin Dam, the centerpiece of the Animas-La Plata Project that will impound 120,000 acre-feet, began in 2005. The reservoir, to be named for former Colorado Senator Ben Nighthorse Campbell, is expected to be filled in 2011. The history of the Animas La-Plata project reflects how difficult it can be for western water projects to move from planning to construction. The process today is far more complicated than during the 1950s and 1960s. Although future storage dams may be built within the Colorado River basin, the Animas-La Plata experience offers little evidence that they will be built quickly. SOURCES: http://www.usbr.gov/uc/progact/animas/background.html; Rodebaugh (2005).

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability municipalities may still wish to pursue the option of constructing a new water storage reservoir(s). Viable prospects for new project construction in the near to medium term, however, are limited: “Except for the Central Utah Project, as recently modified by Congress, and perhaps the Animas-La Plata Project, it seems unlikely that other major water storage facilities will be constructed in the Colorado River Basin in the foreseeable future” (MacDonnell et al., 1995). Although a diversion dam on the Virgin River has been discussed, there is no current proposal to build such a project, and it is one of the few dam projects that has even been discussed in the basin in recent years. An interesting chapter in the history of efforts to augment Colorado River basin water supply storage involves various plans to import water from outside the basin. The most ambitious of these was the North American Water and Power Alliance (NAWAPA), an engineering scheme proposed in 1964 by the Ralph M. Parsons Company of Pasadena, California. The plan envisioned moving large quantities of water from water-rich regions of Alaska and the Canadian Yukon to the arid western United States through a complex system of reservoirs, tunnels, pumping stations, and canals. Dams were also to generate hydropower, sales of which were to help finance project construction. The Parsons Company 1964 cost estimate was $80 billion, adjusted to $130 billion in 1979. The price tag in today’s dollars would undoubtedly be in the hundreds of billions. Political and environmental objections would also impede, and likely block, attempts to revive even a scaled-down version of the NAWAPA scheme. Similarly, prospects of towing icebergs south from Alaska or other arctic regions to augment Colorado River water supplies are equally unrealistic. Declining prospects for traditional water supply projects are perhaps more correctly seen not as an end to “water projects” but as part of a shift toward nontraditional means for enhancing water supplies and better managing water demands. The following sections of this chapter examine some nonstructural and nontraditional means of augmenting water supplies. CLOUD SEEDING Weather modification, including cloud seeding to increase rainfall and suppress hail, has long generated interest among scientists, public officials, and private practitioners in a dozen or more nations. Cloud

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability seeding has been studied and practiced in the United States for at least five decades. Over this period, research investment by agencies of the federal government has waxed and waned. Early experiments conducted by the U.S. Weather Bureau in the late 1940s showed sufficient promise that federally sponsored efforts were scaled up in the 1950s with programs overseen by the Weather Bureau, the U.S. Air Force, and the National Science Foundation, all of which supported cloud seeding research into the 1960s and 1970s. The mid-1970s marked a high point of federal support for cloud seeding, and the National Weather Modification Act of 1976 spurred federal research efforts and mandated a Department of Commerce Weather Modification Advisory Committee to coordinate research among federal agencies. In this same time frame, assessments were made of scientific progress made over the preceding decade and a half. The assessments include a series of reports from both the National Research Council (NRC) and the National Science Board that concluded that experimental evidence for cloud seeding had not yet definitively established its scientific efficacy (NRC, 1964, 1966, 1973; NSB, 1966). The National Research Council subsequently (in 2003) issued a report on the prospects of cloud seeding and other weather modification techniques, concluding that: There is still no convincing scientific proof of the efficacy of intentional weather modification efforts. In some instances there are strong indications of induced changes, but this evidence has not been subjected to tests of significance and reproducibility. This does not challenge the scientific basis of weather modification concepts. Rather, it is the absence of adequate understanding of critical atmospheric processes that, in turn, lead to a failure in producing predictable, detectable and verifiable results (NRC, 2003). In 2004 the Weather Modification Association (WMA) assessed the NRC report from the perspective of those involved in operational weather modification (Orville et al., 2004). This review supported many of the NRC report’s recommendations but also included some criticisms; specifically, the WMA claimed that the NRC report did not adequately account for recent field applications for precipitation enhancement and hail suppression. Since the NRC and WMA reports were issued, some scientists have sought common ground with operators to develop a cloud seeding program that would include scientifically controlled watershed experiments (Garstang et al., 2004).

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability Federal support for cloud seeding research has generally declined since the mid-1970s. Nevertheless, several parties and states in the Colorado River basin maintain a strong interest in the prospects of cloud seeding to increase precipitation. For example, in a 2005 letter to the Secretary of the Interior, the Governor’s Representatives on Colorado River Operations sought to work with the Department of the Interior “to implement a precipitation management (cloud seeding) program in the basin (both Upper and Lower)” (Governors, 2005). In light of the stress on federal funding for discretionary expenditures, a renewed large-scale, federally led weather modification initiative does not appear likely (AAAS, 2006). For the foreseeable future, weather modification experiments and operations will depend mainly on funding from state governments, local communities, and private-sector entities (e.g., utility companies). Six of the seven Colorado River basin states presently support some type of precipitation or snowpack augmentation operations (WMA, 2005). The most prominent cloud seeding project in the basin may be one sponsored by the Wyoming Water Development Commission. This 5-year project is designed to demonstrate if rainfall and snowpack in the state’s mountainous regions can be enhanced (see http://www.rap.ucar.edu/projects/wyoming/). Cloud seeding operations are planned in the Wind River Mountains and the Medicine Bow Range/Sierra Madre Mountains. The program is important because of its potential scientific and operational evaluation for the Colorado River basin states and because the 5-year program is to utilize a solid scientific base for the experiments. If the Wyoming pilot trials increase snowpack by 10 percent, the additional yield would, on average, be on the order of 130,000 to 260,000 acre-feet of additional runoff each spring (WWDC, 2006), which would represent a notable increase in water supplies. In addition to the Colorado River basin states, entities such as municipalities and the ski industry are interested in the prospects of augmenting water supplies and snowpacks by cloud seeding. Denver Water, for example, commenced cloud seeding again in 2002 after 20 years of putting its program on hold. Denver Water’s cloud seeding program was reinitiated as a response to the 2002 drought and was conducted through March 2003 (see http://www.denverwater.org/cloud_seeding.html). In evaluating the success or benefits of cloud seeding operations, the experience of six decades of experiments and applications that failed to produce clear evidence that cloud seeding can reliably en-

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability hance water supplies on a large scale should be kept in mind. Of course, clear evidence is difficult to produce in cloud seeding experiments, as they are not amenable to case-control studies. Furthermore, such experiments are seen by many as being relatively inexpensive even if they do not definitively result in greater precipitation. Given increasing demands for water across the Colorado River basin, cloud seeding is likely to continue to be pursued as a means for augmenting water supply. DESALINATION Scientists and engineers, governments, and advocacy groups have long investigated desalination as a means of augmenting freshwater supplies. Most attention has been directed to converting seawater to potable freshwater, while less attention has focused on subterranean and surface brackish water desalination. There have been steady scientific and engineering advances in the technologies of salt water conversion, and several desalination facilities have been constructed. Advances in technology have led to cost reductions, improved efficiency, and an increase in the numbers of desalination plants worldwide. One recent estimate places the total number of desalting plants at 7,500, capable in total of producing several billion gallons of potable water per day (http://www.waterdesalination.com). Nearly half the world’s desalinated water production today is in the Middle East; about 15 percent of the world’s desalinated water is produced in North America (Wangnick, 2002). In California there are currently 16 coastal operating or planned desalination facilities (http://www.coastal.ca.gov/desalrpt/dsynops.htm). The San Diego County Water Authority is committed to desalination, and by 2020 expects 15 percent of its supply to come from desalination (http://www.sdcwa.org/manage/sources-desalination.phtml). In addition to interests of municipalities and utilities for coastal desalination facilities, energy companies are operating small desalination plants on offshore oil and gas exploration and production rigs; there are nine rigs with desalination facilities off the coast of California (California Coastal Commission and State Lands Commission, 1999). Not all desalination initiatives have proven fully successful, however. For example, in 1999 water authorities jointly sponsored a privately financed desalination plant at Tampa Bay, Flor-

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability ida, to supplement freshwater supplies for their 1.8 million customers. As of May 2006, the plant was not in operation, being plagued by management and technical problems (Cooley et al., 2006). The experience of the City of Santa Barbara, California represents another prominent example of the challenges associated with large-scale desalination (see Box 4-2). Recent improvements in desalination technology have led to energy cost reductions per unit of water produced. There is, for example, a variety of membrane technologies such as reverse osmosis, nanofiltration, and ultrafiltration. These all remove salts, dissolved organics, bacteria, and other seawater constituents from salt water (Pankratz and Tonner, 2003). There is also a range of thermal technologies that boil or freeze water, then capture the purified water while the contaminants remain behind. Energy requirements and costs are important considerations in desalination projects and greatly affect construction plans and decisions in the United States (especially as compared to areas such as the Middle East, where oil and natural gas costs are heavily subsidized). Energy costs notwithstanding, relative production costs have fallen since the early 1990s and the capacity of facilities has risen (AMTA, 2005). In the United States there is some interest in coupling future desalination plants with new power plant production for cogeneration to reduce energy cost in desalination; rising energy costs, however, make it unclear if this trend will continue (Cooley et al., 2006). On the other hand, technical advances may continue and increase desalination efficiency even if energy costs rise. For example, a team led by scientists from the Lawrence Livermore National Laboratory estimates that a membrane system using carbon nanotubebased membranes may be able to reduce future costs of desalination by 75 percent compared to current reverse osmosis membrane technology (Holt et al., 2006). Longstanding federal research and development programs for desalination have been advanced by a series of congressional authorizations, such as the Water Purification and Desalination Act of 1996 (P.L. 104-298). An NRC report reviewed the Bureau of Reclamation’s desalination and water purification program and offered recommendations for program improvement (NRC, 2004). State governments and municipal water districts are also investing in desalination research, development, and demonstration facilities. The Bureau

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability BOX 4-2 Desalination in Santa Barbara The City of Santa Barbara, California, relies heavily on rainfall and local groundwater to meet its water supply needs. These sources were impacted by severe drought conditions between 1987 and 1992, which caused sharp declines in local reservoir levels. The water shortage led city officials to consider a new source(s) of water supply, and Santa Barbara residents approved construction of a desalination plant to augment the city’s water supplies (they also approved a piped connection to California’s State Water Project). Construction of a reverse osmosis facility began in 1991 and was completed in 1992. The plant successfully produced water during its testing phases, but soon after plant completion, drought conditions in the region subsided. The plant was placed on active standby mode because of the high costs of producing water during nondrought periods. At the same time, the higher costs of water driven by the desalination plant and the connection to the State Water Project contributed to declining water demands. Conservation measures enacted during the 1987-1992 drought, such as low-flow toilets and xerophytic landscaping, contributed to water savings, and per capita demands never rebounded to predrought levels. The desalination plant today is decommissioned, with a large portion of the plant’s infrastructure having been sold to a company in Saudi Arabia. Today, the plant serves as an “insurance policy, allowing the City to use its other supplies more fully” (http://www.santabarbaraca.gov/Government/Departments/PW/SupplySources.htm?js=false). Although the plant is not currently operational, its future will bear watching as California’s population continues to grow, as the City of Santa Barbara continues to strive for urban water efficiencies, and as the economics of energy and water production continue to shift. SOURCE: Cooley et al. (2006).

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability of Reclamation has recently focused its desalination research and development strategies in three areas: grants to university scientists, studying the feasibility of reopening the Yuma desalination plant, and constructing a test facility at Alamogordo, New Mexico to explore the feasibility of desalting brackish groundwater. Beyond energy costs, desalination entails several environmental implications. A key barrier to economically viable desalination is disposal of the briny water that is a byproduct of the process. This is especially a problem in areas that do not have access to the ocean, but it can also be problematic for coastal locales. For example, native species in bays and estuaries are impacted by large seawater intake and by discharge of briny concentrates that are byproducts of desalination processes. Drawdown of brackish water in subterranean reservoirs can lead to ground subsidence and/or a lowering of the water table. Regulations and technologies to mitigate adverse possible environmental effects associated with desalination have been and will continue to be implemented by municipalities, states, and the federal government. Technical, economic, and environmental issues notwithstanding, desalination offers the Colorado River basin states an option for actually increasing water supplies. This option is limited primarily to areas with access to water derived from the Pacific Ocean, although there may be other, select Colorado River basin sites at which desalination facilities may be feasible (e.g., Yuma, Arizona). With increasing regional water demands, and with increases in technical efficiencies, desalination is likely to be perceived as an increasingly attractive option for augmenting supply, which will be especially true for wealthier communities. Prospective desalination projects will have to address and overcome the barriers of its energy requirements and acceptable means of disposing desalination’s highly saline byproduct. Because of both its prospects and its potential limitations, desalination will also continue to be an important topic of research (see, e.g. http://watercampws.uiuc.edu/, which is a National Science Foundation-sponsored center for the study of materials and systems for safely and economically purifying water for human use).

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability REMOVING WATER-CONSUMING INVASIVE SPECIES Since settlers began moving into the southwestern United States in the mid-19th century, many invasive species have been purposively or inadvertently introduced to the region. These include cheatgrass, camelthorn, ravenna grass, Russian olive, and tamarisk, or salt cedar. These species are identified by the National Park Service as the greatest threats to Grand Canyon National Park’s native species (NPS, 2005) and are capable of surviving in a variety of habitats. They are today prolific within the park, representing approximately 10 percent of the vegetation (USGS, 2005). Tamarisk (Tamarix ramosissima) is an invasive plant of special concern across the basin. Tamarisk consumes large quantities of water, crowds out native riparian species, and can lead to ecosystemlevel changes. Tamarisk forms dense stands and is difficult to eradicate. Starting in the 1850s, several tamarisk species were imported to the United States as ornamentals and for use in erosion control (http://www.invasivespeciesinfo.gov/council/ismonth/archives/tamarisk/tamarisk.html). The plant eventually made its way to the Colorado River basin and spread upstream along the Colorado River to the lower end of Grand Canyon National Park in the 1930s. It did not take hold in Grand Canyon National Park or in the upper Colorado River basin, however, until large dams were constructed upstream in the 1960s (tamarisk had been previously controlled by large spring runoff from Colorado, Utah, and Wyoming flowing into the Grand Canyon). Tamarisk is a dominant riparian plant species today across the basin, consuming considerable amounts of water that would otherwise be available to downstream states or available to support ecosystem goods and services. For example, in Colorado it is estimated that tamarisk occupy roughly 55,000 acres and consume 170,000 acre-feet of water per year more than the native replaced vegetation (Colorado DNR, 2004). Smaller-scale efforts to control and remove tamarisk in the 1990s have led to more ambitious programs in the Colorado River basin and on other western rivers. A variety of efforts have been used to try to remove tamarisk, including herbicide injection, stump removal, deliberate flooding, and the use of a leaf beetle (Diorhabda elongata) and its larvae to eat tamarisk leaves. In 2002 the National Park Service, with support from environmental organizations and some 1,500 volunteers, began removing tamarisk from 63

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability tributary canyons along the Colorado within Grand Canyon National Park. To date, more than 180,000 tamarisk trees have been removed from 1,819 hectares in the park (NPS, 2006). AGRICULTURAL WATER CONSERVATION Agriculture water conservation in the western United States has long been an issue of widespread concern and importance. There are clearly inefficiencies in agricultural water applications in the West, some of which relate to difficulties in precisely matching water applications to plant water requirements (which will vary in response to changing temperature and soil moisture conditions). In addition, unused irrigation water on one farm usually generates return flow that is reused downstream by other irrigators and also helps sustain ecological habitats. Farm-level irrigation efficiency is of great importance to individual farmers; nevertheless, water withdrawals are “lost” from the stream reach from which they are withdrawn, which has ecological effects on instream flows and habitats.1 Deep percolated water that finds its way to the groundwater table, however, may find its way back to a stream channel farther downstream. Farmers often periodically flush water through the soil profile in order to prevent excess salt accumulation in the crop root zone—especially if irrigation water is of marginal quality. This salt leaching practice is essential to successful irrigated agriculture (English et al., 2002). Leaching of salts from the root zone can, however, increase salt loading to streams and aquifers, which was one of the processes addressed in the Bureau of Reclamation’s Colorado River Basin Salinity Control Program (which was mentioned in Chapter 2). There are opportunities for agriculture water conservation even in basins where water use efficiencies are high. Increased on-farm efficiencies can reduce production costs, improve water distribution among farmers and other users, and reduce negative, off-farm effects of irrigation (Wichelns, 2002). One concept, although not new, is the idea of managing irrigation water as a means to maximize profit, not yield. Production of the final increment of crop yield requires disproportional amounts of water, 1 From the perspective of the entire Colorado River basin, water that is reused downstream in the form of return flows is not lost, whereas water that evaporates from the soil, or that is transpired by phreatophytes or weeds, is lost to agriculture and other potential uses.

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability which can be relatively expensive. A strategy of not applying these additional units of water to gain this (relatively expensive) additional, final increment of production can save considerable amounts of water (Kelly and Ayers, 1982). There is also potential to employ different cropping patterns, such as rotations containing both sensitive and salt tolerant crops. It may be possible to grow a salt-sensitive crop, followed by a salt-tolerant crop, before salinity reaches unacceptable levels and soils must be leached (English et al., 2002; Manguerra and Garcia, 1996). Research on water use efficiency has been under way for years, including studies of water efficient technologies and ways of providing economic incentives and technical support for irrigators who adopt them (e.g., in the Grand Valley Unit with Reclamation’s Salinity Control Program). Irrigators will no doubt continue to innovate in managing their irrigation systems, taking advantage of remotely sensed soil moisture content and the state of crop growth—this latter approach includes deficit irrigation in which plants can be stressed at noncritical times but are properly watered at critical flowering and fruiting stages (English and Raja, 1996; Jurriens et al., 1996; Trimmer, 1990). Irrigation advisory services exist to provide assistance to farmers on these advanced techniques (English et al., 2002). In addition, some improvements in irrigation water productivity will likely result from better agronomy and cultivars, perhaps with genetic modification. There may also be prospects to increase water available for urban and instream uses by retiring some agricultural lands. URBAN WATER CONSERVATION As the Colorado River states have urbanized, growing water demands have stimulated more and more urban water conservation programs in many communities. These programs include water conserving technologies (e.g., lower-flow plumbing fixtures and more efficient irrigation systems), market incentives, regulatory policies, new landscaping techniques and the use of drought-tolerant (xerophytic) plants, and public education announcements encouraging urban water conservation. Elected officials today often promote water conservation plans to their constituencies and many citizens are willing to adopt household level water-saving practices. Many plumbing fixtures, such as toilets and shower heads, use less water than in a previ-

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability ous generation. This has given rise to periodic revisions of building codes and policies for retrofitting older commercial and residential structures. Use of reclaimed (or “gray”) water for landscaping, golf course irrigation, and augmenting return flows to the Colorado River has also increased. The Southern Nevada Water Authority (SNWA), for example, reported the use of almost 22,000 acre-feet of reclaimed wastewater in its service area in 2003 (SNWA, 2004). A 1998 report from the NRC reviews the engineering, public health and policy issues associated with reclaimed water. That report focuses on implementing safe, potable standards for indirect uses, such as adding reclaimed water to other water supplies, then treating the mixed reclaimed and ambient water to conventional treatment standards. Although there are instances in which reclaimed wastewater represents a viable option, the report also identifies possible pitfalls in its applications (NRC, 1998). Given rapidly growing urban water demands across the West, the impacts of increasing demands on reservoir storage levels and ecosystems, and the potential for urban water conservation and efficiency programs, there is widespread interest in approaches and technologies to help reduce urban water demands. Examples of recent studies, projects, and conferences in the West on this front include the following: The Bureau of Reclamation’s Yield and Reliability Demonstrated in Xeriscape project. This study evaluated potential water savings and maintenance and installation costs associated with water-conserving landscapes. It was funded by the Bureau of Reclamation with in-kind services by seven participating municipalities and water districts in Colorado's Front Range. The final report was completed in December 2004 (Medina and Gumper, 2004). Industry-sponsored conservation studies and projects, such as those from the Aquacraft firm in Boulder, Colorado (http://www.aquacraft.com/Services/water%20conservation.htm). An American Water Works Association 2006 symposium in Albuquerque, New Mexico (http://www.awwa.org/conferencessources/?CFID=14981257&CFTOKEN=69080727).

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability A series of water efficiency workshops and studies sponsored by Western Resource Advocates of Boulder, Colorado (http://www.westernresourceadvocates.org/water/wateruse.php). Across the Colorado River region there are numerous approaches to managing and conserving urban water supplies. Some municipalities, such as Tucson, have aggressive and long-standing programs (see Box 4-3). The SNWA has instituted municipal and industrial conservation programs among the seven water and wastewater agencies that comprise its members (SNWA, 2004). Some of these have been quite useful; for example, SNWA estimates that Las Vegas area water use decreased by roughly 50,000 acre-feet per year between 2002 and 2005 because of implementation of a drought plan and a “Water Smart Landscape” program (Fulp, 2005a). Per capita water uses in the Colorado River basin’s cities vary widely, from roughly 170 gallons per capita per day (gpcd) in Tucson to over 300 gpcd in some other cities in the basin (although because of the probability for comparison errors in this variable, these figures should be considered individually rather than as absolute comparisons; WRA, 2003). These differences reflect a large number of variables, including age of household water fixtures, conservation programs, municipal ordinances, water prices, and urban landscape expectations and norms. They also suggest room for improvement in urban water conservation and efficiencies, and the value of disseminating lessons from successful urban water strategies in individual cities to other cities across the region. Knowledge of useful water conservation practices and techniques has diffused across the region through the efforts of groups such as the Colorado River Water Users Association. Nevertheless, there have been few efforts to systematically compare and evaluate the breadth and variety of these water conservation initiatives. One exception is a 2003 study from Western Resource Advocates that compares urban water uses across the southwestern United States (WRA, 2003). Efforts at comparing urban water management across the region, and sharing knowledge of successful experiences, could be enhanced by more formal water conservation program collaboration, and some mechanisms have been created to coordinate and support urban water programs (see, for example, the activities of the California Urban Water Conservation Council; http://www.cuwcc.org/home.html). Such efforts point to the prospects for improved

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability regional urban water management and enhanced preparedness for managing water in periods of drought and water shortages. OFFSTREAM WATER BANKING AND RESERVES Water banking and groundwater recharge programs have been used for many decades in the western United States, and there has been an especially strong interest in these programs during the past decade. The term “water bank” generally applies to two different types of arrangements: (1) groundwater storage projects, and (2) arrangements to facilitate voluntary water transfers through rental markets (http://www.isse.ucar.edu/water_climate/banking.html). Water banking and groundwater storage programs have several objectives, which include (1) the (hoped-for) creation of reliable supplies during extended drought, (2) the promotion of water conservation by encouraging “deposits” into groundwater storage, and (3) the recharging of groundwater tables and reduction of evaporation from surface reservoirs. From a geological perspective, large amounts of water can often be infiltrated, via gravity, into under ground aquifers in many locations. However, during drought conditions, large amounts of water may need to be withdrawn in a very short period of time, which often entails significant pumping costs. Groundwater storage programs aim to facilitate water transfers in response to short-term changes in supply-and-demand conditions, with the goal to bring together people seeking to purchase water with people interested in selling water entitlements (Frederick, 2001; MacDonnell et al., 1995). Salient featuresof recent initiatives involving banking and exchanging Colorado River basin water are discussed below. The State of Arizona created its first framework for water banking in 1986, with passage of legislation to authorize underground storage and recovery projects. In 1996 the Arizona Water Banking Authority (AWBA) was established. The AWBA focused on storing surplus Colorado River water through groundwater recharge and on protecting Arizona’s Colorado River supplies by demonstrating the state’s commitment to using its full allocation. This groundwater supply could subsequently be drawn upon for use during shortages of Colorado River flow, during Central Arizona Project service disruptions, to assist in meeting management objectives of the Arizona Groundwa-

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability BOX 4-3 Water Conservation in Tucson Water conservation programs for the City of Tucson, Arizona, offer an interesting case study for several reasons. First, some of the programs date back to the 1970s and are among the oldest urban water conservation efforts in the region. Second, these programs have included several different aspects including public education, water-saving technologies, water pricing, and regulation. Third, the Tucson Water Department has maintained an excellent database on its conservation programs and now, after four decades, has a compendium of valuable information. Finally, Tucson has constantly revised its policies and strategies to incorporate newer, efficient technologies, updated water pricing and revised regulations, for example, codes for low-water-use landscaping (xeriscaping) and drip irrigation systems. In 1973 Tucson annual per capita water use reached an all-time high of 205 gallons per day. The city was unprepared to ensure reliable service, a warm summer in 1974 led to increased water use rates, and both household and industrial growth were accelerating. Although reliability of service was largely a summertime peak demand issue, the city instituted year-round water conservation policies. Through a series of measures, water consumption dropped to roughly 150 gallons per capita/day, counting both household and industrial users. Tucson’s urban water conservation program is built around five interrelated strategies: ter Code, and to assist in meeting Native American water rights claims settlements. The AWBA also provides some insurance to offset liabilities associated with the Central Arizona Project’s junior water right, which is subordinate to California’s 4.4 million acre-feet per year Colorado River allocation. By 2000 the AWBA was recharging about 294,000 acre feet per year of water (http://www.awba.state.az.us/backgrnd/update.html). The practice allows storage of portions of the state’s allotment that are not utilized at present and storage of surplus water during years of high river flow. Water is recharged into suitable geologic basins in western and southern Arizona, where it is not susceptible to evaporation and where it can be accessed with relatively modest pumping costs. In 1999 the Secretary of the Interior published regulations defining the procedure for the lower basin states to engage in interstate offstream storage agreements (see 43 CFR 414.3). These regulations

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability general public information, education and training programs, incentive programs, direct assistance, and regulatory measures. The City of Tucson began delivering reclaimed water in the mid-1980s; a large percentage of parks, golf courses, and other public spaces today are irrigated with reclaimed water. Beyond the 1980s, domestic household usage rose to about 170 gallons per capita per day (gpcd) and has since been relatively stable. Xeriscaping is mandated by building code. Tucson maintains data for analysis (e.g. gpcd water consumption in single-family and multi-family dwellings) and water use trends are studied. Tucson’s programs have been complemented by state legislation. For example, the Arizona Department of Water Resources code established standards for the reduction of per capita water use. Tucson’s water plan since 1990 has included periodic assessment of the effectiveness of programs, development of ways to continue promoting the five-part conservation strategy, and infrastructure improvements that capture lost water (e.g., replacement water pipelines to reduce water losses through leaks). Today Tucson is looking to a new conservation plan to guide water uses over the next two decades (more information on Tucson Water is available at http://www.ci.tucson.az.us/water/). set the groundwork for a subsequent interstate water banking agreement (a storage and interstate release agreement, or SIRA) among the AWBA, the Colorado River Commission of Nevada, and the SNWA. A 2004 amendment to an existing agreement with AWBA allows the Nevada water agencies access to 1.25 million acre-feet of water in the Arizona Water Bank. Banked water is stored in the form of “credits.” For Nevada to recover its storage credits, Arizona will use banked water and forego the credited amount of Colorado River water to Nevada. The Nevada agencies will then divert water from Lake Mead (Davenport, 2005; SNWA, 2006). In 2004 the Metropolitan Water District of Southern California entered into a similar, but smaller scale, water banking agreement with the SNWA and the Colorado River Commission of Nevada (Davenport, 2005) that establishes terms and conditions for offstream storage of Colorado River water in Southern California and provides storage credits for SNWA (DOI and USBR, 2006). In the future, these and other innovative types of interstate groundwater storage and banking initiatives are likely to be im-

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability plemented elsewhere in the Colorado River basin where there are willing parties, where requisite geologic and other physical conditions exist, and where necessary institutional changes can be made. A related concept being explored in the basin involves the creation of water reserves, which is not to be confused with the concept of reserved rights that can exist under the doctrine of prior appropriation (Box 4-4 discusses aspects of a recent water reserve proposal in the State of New Mexico). The concept of water reserves generally entails the storage of water, either by excess flows in wet periods or via water rights sales, leases, or transfers, to be used at a later date for a specific purpose(s). It is a variant on the water banking concept in that it is not necessarily fully market-based and may be designed to benefit public and nonmarket values (e.g., instream flows). Box 4-4 New Mexico’s Strategic Water Reserve A proposal to create a strategic river reserve in the State of New Mexico was offered in 2003. The proposal was drafted by Think New Mexico, a research institute that sought to raise awareness regarding the state’s fully allocated and overallocated rivers, the high cost of prior water litigation in the state and with neighboring states, water needs for agriculture and environmental purposes (e.g. endangered species in the middle portion of the Rio Grande), and increasing demands that population growth was placing on the state’s five major rivers. Think New Mexico recommended that the legislature enact and fund a strategic river reserve. The concept was endorsed in the legislature and was promoted through editorials and community-based support. The New Mexico governor called for the reserve in his 2005 state-of-the-state address. A strategic water reserve bill was enacted in the first session of the 47th legislature in 2005 and funded in the 2006 second session in the amount of $4.8 million. The fund is administered by the New Mexico Interstate Stream Commission, which will purchase or lease water rights that become available and redeploy them for public purposes including agriculture, endangered species, and assurance that the state meets its obligations for interstate water transfers, especially downstream in the Rio Grande and Pecos rivers to Texas. SOURCE: Think New Mexico (2003); NM Statute 72-14-3.3 et seq.

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability COMMENTARY There has been a wide range of engineering and political efforts designed to overcome the water supply limitations imposed by the aridity westward of the 100th meridian. There are technological means available to extend water supplies in the Colorado River basin and elsewhere, but all these options have limits. Although limited opportunities exist to construct additional reservoirs or to implement interbasin water transfers into the Colorado River basin, these have diminished from a previous era. Changing economics and demographic conditions may increase the viability of such traditional projects at some point in the future, but immediate prospects for major new water supply reservoirs or interbasin transfers are limited. Consequently, new water project prototypes that emphasize conservation, landscaping, new technologies, and other measures are being promoted across the West. Desalination certainly represents an alternative for augmenting water supplies in some circumstances but it can be expensive and may not always be feasible. Disposal of brine water can be problematic, for example, and in many instances desalination is a realistic option only for coastal cities. Cloud seeding may offer marginal opportunities for increasing supply—especially in the upper basin states—but it does not appear to offer a reliable long-term means for increasing precipitation and water supplies. Groundwater banking and offstream water reserve programs have proven useful in many instances and are being used in more areas and instances but they are limited by geologic conditions. Agricultural-urban water transfers are also likely to be effected more often in the future. As noted in Chapter 2, such transfers represent lucrative opportunities for both buyers and sellers and often entail third-party effects, all of which are important to consider when negotiating water leasing and transfer arrangements. Given the projections of both increasing regional population and increasing regional temperatures, along with tree-ring-based reconstructions that demonstrate the recurrence of severe drought conditions across the Colorado River region, urban water conservation will become only more important. Future augmentation of urban water supplies can, and will, be achieved through a variety of water conservation, pricing, and other measures. Water consumption and conservation practices are strongly related to water prices, incentives, and regulations. If water prices markedly increase, people and businesses

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Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability will use less water; however, water prices have always been tied closely to political decisions and this is not likely to change in the near future. Incentives can help reduce per capita water use, as can tighter regulations and fines for excessive water use. There have been many studies and reports regarding what might be accomplished through nonstructural measures designed to conserve water (e.g., Gleick et al., 2005). Clearly, there are gains to be realized through aggressive water conservation measures. There is no formal basin-wide strategy or program designed to promote urban water conservation across all cities. There are, however, programs such as the California Urban Water Conservation Council that supports statewide urban water use programs, and other, similar efforts could lead to further water use efficiencies. But broadly speaking, none of the technological or strategic options for either increasing or conserving and extending water supplies examined in this chapter directly confronts the relationships between urban population growth, water demands, and limited water supplies in this arid region. Technological and conservation options for augmenting or extending water supplies—although useful and necessary—in the long run will not constitute a panacea for coping with the reality that water supplies in the Colorado River basin are limited and that demand is inexorably rising. Proper water management under normal climate and hydrologic conditions poses many challenges, and under drought conditions, such challenges are greatly magnified. This is an especially important concern given regional warming trends and long-term climate studies indicating that long-term droughts recur periodically across the Colorado River basin. Chapter 5 lists some important issues in adjusting to drought and identifies and discusses some of the key organizations and programs focused on improving drought preparedness in the Colorado River region.