INTRODUCTION COLORADO RIVER BASIN -

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1 32 Controlling Salinity in the Colorado River Basin, The Arid West AI R. Jonez Chief, Colorado River Water Quality Office Bureau of Reclamation U.S. Department of the Interior Denver, Colorado INTRODUCTION The Colorado River is the lifeline for more than 17 million people in seven arid States and Mexico. The river, while nearly pure at its origins in the snowcapped Rocky Mountains, carries about 8 million megagrams (9 million tons) of mineral salts annually past Hoover Dam. The salt pollution damages irrigated crops, causes accelerated plumbing replacement and appliance wear, and causes annual damages of over $120 million. Projections are that without any controls, annual damages of over $238 million will occur by about The Department 0 f the Interior, the Department of Agriculture, and the Environmental Protection Agency are working with the Colorado River Basin Salinity Control Forum members, State governments, and the public to reduce salt contamination. COLORADO RIVER BASIN - SETTING One of the most arid regions of the West is nourished by the majestic Colorado River. High in the Rocky Mountains, the Colorado begins its journey to Mexico and the Gulf of California, a distance of 2250 kilometers (1400 miles). The river travels through seven States where some of America 1 s most magnificent natural features are found. Along its path are found Rainbow Bridge, which is as high as the United States Capitol Building, and the Grand Canyon, almost a mile deep, exposing millions of years of geologic history. The Colorado is a river of life, providing recreation for thousands, water for cities and industries, and water 337

2 for irrigation of over 405,000 hec tares (1 mi Ilion ac res). More than $1 billion of crops are grown year round in some parts of the basin. The mighty Colorado has been harnessed to provide a dependable water supply, flood control, and power generation in the basin. Hoover Dam and Glen Canyon Dam's reservoirs store four times the annual virgin yield of the river. The longtime average historic virgin flow of the Colorado River at Lee Ferry is about 18.5 x 109 m3 (15.0 million acre-feet) per year. [Lee Ferry, the boundary between the Upper and Lower Basins, is in northern Arizona approximately 1.61 kilometers (1 mile) downstream from the Paria River or 27 kilometers (17 miles) below the Glen Canyon Dam.] Average annual precipitation across the basin varies from as low as 0.05 meter (2 inches) in the desert areas to as much as 1 meter (40 inches) in high mountain catchments. PROBLEM The Colorado's most insidious problem is "increasing salinity." By the time the Colorado reaches Hoover Dam, it is carrying more than 8 million megagrams (9 million tons) of salt annually. Salt Sources About half of the present salt pollution comes from natural sources, including mineral springs and geysers. As the water passes through ancient marine deposits and saline soils, salts are continually washed into streams. Added to that is the concentrating effect of man's use - use of water for irrigation or municipal and industrial use, and reservoir evaporation. (See Figure 1.) \ 47% Natural Sources ----l '-\i-- 37% Irrigation /~ I 12% Reservoir Evaporation I \ J 3% exports 7' 1% M&I The Colorado River, at its headwaters in the mountains of Colorado, has a salinity concentration of only about 50 mg/l. The salinity concentrations progressively increase downstream as a result of the consumptive use of water and salt contributions. In 1982, the salinity concentrations averaged 825 mg/l at Imperial Dam, the last major diversion point on the Co lorado River in the Uni ted States. Wi thout control measures, the concentration is projected to increase, possibly reaching a level of 1089 mg/l at Imperial Dam by the year Physical and Economic Impacts Average annual economic losses of $120 million from increasing salinity in the Lower Basin of the Colorado are impressive. Salt pollution affects more than 10 million people and hectares (1 million acres) of irrigated farmland in the United States. About 70 percent of the economic losses are associated with municipal and industrial use and occur when salinity concentration levels are above 500 mg/l. The losses are primarily from increased water treatment costs, accelerated plumbing replacement and appliance wear, and increased soap and detergent needs. The unpalatable taste, causes some water users to purchase bottled water or home water softners. The Environmental Protection Agency recommends drinking water supplies contain less than 500 mg/l of total dissolved solids, and yet many communities have no choice. For irrigators, the higher concentrations cause decreased crop yields, altered cropping patterns, higher leaching and drainage requi rements, and higher management costs. Economic losses to agriculture (either through lower yields or higher production/management costs) usually begin when salinity levels of applied irrigation water reach 700 to 850 mg/l, depending upon soil conditions and type of crop grown. It is estimated that average annual damages in January 1983 dollars to lower Basin water users are at least $540,000 for each rise of 1 mg/l in salinity concentrations at Imperial Dam (over the range of future projected salinity levels). SALINITY CONTROL ACTIVITIES Title I and Title II Relationships Figure 1. Sources of salinity concentrations in the Colorado River Basin. 338 Public Law , the Colorado River Basin Salinity Control Act, was passed in June Under Title I, 339

3 programs downstream from Imperial Dam, the Secretary was authorized to (1) construct a major desalting plant and appurtenant works (intake pumping plant system, etc.) to treat the Wellton-Mohawk drainage waters, (2) extend the Wellton-Mohawk drain by 85 kilometers (53 miles) to the Gulf of California, (3) line or construct a new Coachella Canal in California, (4) reduce Wellton-Mohawk irrigable acreage from the hectares ( acres) authorized in the Gi la Reauthorization Ac t to hec tares ( acres), improve Wellton-Mohawk irrigation efficiency so as to reduce the quantity of "return flow" drainage water to the river, and (5) construct a regulatory and protective well field along the international border. Title II relates to activities above Imperial Dam, about which this paper is directed. The status of these activities is discussed later. Before further examining the Colorado River Water Quality Improvement Program (CRWQIP), a review is needed of the relationship of salinity control and related program objectives of Public Law to the total dissolved solids (TDS) numeric criteria standards and the Mexican salinity agreement (Minute 242). In formulating plans and management objectives for salinity control and/or augmentation programs in the basin, it is important to differentiate between the TDS numeric criteria for the three stations in the lower basin (Hoover, Parker, and Imperial Dams) and the Minute 242 treaty obligations to Mexico. The two requirements, one established by the Basin States in response to a request by EPA [1] and the other by a treaty with Mexico, are separate and distinct [2]. Specifically, there are no dilution requirements or upper basin salt load reductions necessary to meet our treaty obligations with Mexico. The salt load reduction objectives for Title II programs only apply in meeting the established TDS numeric criteria in the lower basin in the United States. Increases or decreases in TDS at Imperial Dam will be passed on to Mexico without any infringement on treaty obligations so long as the water delivered to Mexico has an annual average salini ty of no more than TDS of ppm over the annual average salinity of Colorado River waters which arrive at Imperial Dam. In order to maintain the di fferential TDS of ppm between Imperial Dam and deliveries to Mexico, the Title I programs, specifically the Yuma desalting complex and related features, are being constructed. The Yuma desalting complex is designed to remove salt loads from Wellton-Mohawk irrigation return flows in order to maintain the established differential TDS under future river conditions. In addition, Wellton-Mohawk return flows currently bypassed to the Santa Clara Slough would be recovered by the Yuma desalting complex. This would reduce the requirement for waters that otherwise are re leased from storage to meet the Minute 242 requirement. It should be noted, however, that there is a common interface between Title I and Title II programs at Imperial Dam. Thus, if the TDS at Imperial Dam is reduced below projected TDS conditions, while maintaining scheduled deliveries to Mexico, the Yuma Desalting Plant may have to operate at higher capacities to maintain the differential salinity to Mexico. Conversely, if surplus water is passed by Imperial Dam, then it is possible that the Yuma Desalting Plant will not have to operate at design capacity to maintain the differential salinity to Mexico. Fortunately, in recognizing the difficulties in predicting future river conditions and establishing operational parameters for the plant, a modular plant design was selected to provide additional flexibility to the system. Research and Projections Figure 2 shows the historical salinity levels at Imperial Dam from 1940 to 1982 and the Colorado River Simulation System (CRSS) projection through the year 2010 without salinity control [3]. While historical trends vary and the historical trace reflects impacts of filling Lakes Mead and Powell, it should be noted that the salinity level trend is again rising. Figure " ; " ".., ---- H.storlcitl PrOjected , W"hu"l W~I'" Q""llly Impro'lilme"t Program Recorded salinity levels at Imperial Dam with CRSS projections through the year

4 In recent years, the Colorado River storage reservoirs have evolved from a filling mode to a full system operating mode. An operational study of the major reservoirs in the basin could take advantage of new information regarding chemical mixing and precipitation phenomena. Ongoing research studies of Lakes Powell and Mead are expected to provide a better understanding of salinity mechanisms in reservoirs. However, the scope of any operational reservoir studies must, of necessi ty, extend into other operational criteria considerations. The operating criteria to meet ongoing irrigation and power generation requirements, as well as flood control, recreation, and fish and wildlife need to be evaluated. The broader scope of such an operational study could provide a more complete picture of the tradeoffs that are inevitably involved in satisfying operational demands. In view of the potential tradeoffs and sensitive nature of existing reservoir operation~, the longterm salinity reduction potential may be constrained by different operational scenarios. Without these oferational studies, the applicable operational regime for salinity control may not be selected through lack of knowledge of the overall effects. Reservoir Studies A study is currently underway to evaluate the impact that the two major reservoirs, Lakes Powell and Mead, have on salinity in the river system. The study is being conducted under a professional services contract and is scheduled for completion in November The contractors are applying a two-dimensional thermal hydrodynamic chemical equilibrium model to Lakes Powell and Mead. The objective of this study will be to track the ion constituent makeup through the reservoir, quantifying any predicted calcite precipitation or gypsum dissolution and evaporation concentration. A generalized prediction technique could then be developed for use in the CRSS for applying a corrective factor to the TDS load in Lakes Mead and Powell. This study would address a longstanding concern that the CRSS model does not reflect any changes in TDS that the reservoirs may impose on the system. The CRSS is a comprehensive mathematical computer model of the Colorado River, simulating both water quality and quantity in the operations of the river. It was developed so it could be adapted to other basins as well. Solute Trend Study The Colorado River Water Quality Office is presently funding a I-year in-house study to investigate trends in the loadings of individual ions in the Co lorado River and its tributaries. This is an attempt to isolate a cause for the apparent change in the relationship of historic data comparing flow to TDS in the post-1965 period. If a physical basis for change can be identified, then the monthly flowsalt coefficients used to develop the "virgin" salt data base from the "virgin" flow data base can be modified, thus providing more confidence in future projections. The study is scheduled for completion in September 1983 and is considered to be a preliminary step in evaluating the need for future constituent ion work in the basin. PROGRESS OF ONGOING ACTIVITIES Alternative ways of solving the salinity problem depend partly upon the way the salt enters the river [4]. More than a third of the salt enters the river from irrigation sources. A map of the units under study is shown in figure 3. Irrigation Source Control Irrigation source control would reduce salt loading by improving irrigation practices that currently leach salts from marine shales and other saline deposits. Reclamation is currently evaluating irrigation controls in Grand Valley, Lower Gunnison Basin, and McElmo Creek Units in Colorado; the Uinta Basin Unit in Utah; and the Palo Verde Irrigation District Unit in California. Improvement of distribution systems and irrigation practices in a11 of these areas appears viable and could reduce the river's salt load by about megagrams (1.0 million tons) per year. Controls in the irrigation areas, particularly Grand Valley, which was authorized in Title II, are moving ahead. In the Grand Valley Stage One area, about 11 kilometers (7 mi les) of the Government Highline Canal have been lined, and construction of, the related closed pipe lateral system is nearly complete. By reducing the leakage from canals and laterals and by improving onfarm efficiencies, the total uni twill reduce the salt load by about megagrams ( tons) annually, with the overall effect of reducing salinity concentrations at Imperial Dam by 31 mg/l. The Department of Agriculture's main thrust in the salinity program is the upgrading of onfarm irrigation

5 CALF UTAH WYOMING "-'-~""'8asm1.lr"ll1 COLO NEW MEX would remove salt from localized areas such as mineral springs, abandoned oil wells, and geysers. The Paradox Valley, Glenwood-Dotsero Springs, and Meeker Dome Units in Colorado and the Las Vegas Wash Unit in Nevada are point sources of salinity currently under investigation. Three wells in the Meeker Dome area have been plugged and ground-water levels are declining, indicating that the to megagrams ( to tons) salt loading per year from that source have been s igni ficant ly reduced. Feasiblity studies are moving forward on the Glenwood-Dotsero Springs Unit. The Las Vegas Wash Unit, authorized for construction under Title II, is being reformulated because of changing ground-water conditions, and it appears that a cost-effective control strategy involving bypassing wastewater around saline soils may be viable. Other unit studies have been concluded because of poor cost-effectiveness or limited salinity control opportunity. A viable control plan is available for the Paradox Valley Unit which also was authorized for construction under Title II. The unit is designed to remove megagrams ( tons) of salt per year by pumping the saline ground-water or brine from shallow wells along the Dolores River, thus preventing it from becoming a part of the riverflow. Reclamation anticipates disposal of the brine through deep well injection. Diffuse Source Control.Title II Salinity Controt Units o Initial Units Authorized for Construction Figure 3. Units of the Colorado River Water Quality Improvement Program. systems and irrigation management - bringing irrigated farming up to a level of current technology; for example, the use of laser land leveling. Point Source Control Another class of salt loading to the river involves identified point sources of salinity. Point source control 344 The third class of control opportunities involves diffuse sources of salt. Diffuse source control measures include watershed management, land treatment, and the collection and disposal of irrigation return flows. Utah's Dirty Devil and Price-San Rafael Rivers Units and Wyoming's Big Sandy River Unit are identified diffuse sources now under study. Investigations of these units include examinat ion 0 f irrigation improvements, vegetat ion and watershed management, and select ive withdrawal and disposal of poor quality streamflows. Preliminary indications are that the Chevron Chemical Company may be able to use a part of the Big Sandy water for a fertilizer plant. The State of Wyoming provided $300,000 and approved the expenditure of another $818,000 to move the study toward completion. Other Alternatives Necessary Under the Colorado River Basin Salinity Control Program, our policy is to prioritize construction so that the most 345

6 cost-effective measures will be implemented to meet program goals. For evaluation purposes, the incremental costeffect iveness of a potential salinity control measure is compared against the cost-effectiveness of other possible control measures to determine whether the specific measure should be implemented. Assuming that all agricultural source units and the Paradox Valley Unit are successfully implemented, we will still need to reduce the river's salt load by more than a million megagrams (1.2 million tons) per year if we are to meet the standards. Diffuse and point source control units currently under study annually produce about 740 x 106 m3 ( acre-feet) of brackish and saline water. The necessary disposal of about half of that looks technically achievable, although expensive. For example, desalting costs would involve capital investment of around $4 billion to meet the established standards with annual operating costs of about $400 million, mostly for energy. Alternatively, evaporation ponds for water disposal would have a cost of about $8 billion with low operation and maintenance costs but would require dedication of about hectares of land ( acres) of land for that purpose. To avoid the structural scenario of energy-intensive desalination plants or vast areas of evaporation ponds, alternative beneficial use concepts must be explored. Reclamation has investigated possible beneficial uses of that water. In a September 1981 Special Report entitled Saline Water Use and Disposal Opportunities [5], Reclamation identified both local use for industrial purposes and longdistance coal transport pipelines as salinity control strategies that appear more cost-effective and environmentally acceptable than the other "structural" measures. The AQUATRAIN project evolved as one beneficial way to use saline water. A discuss ion of AQUATRAIN wi 11 be handled at this Symposium by Mike Clinton, Chief, Saline Water Transport and Use Office. MAJOR ISSUES AND CONCERNS Most of the delays and changes in saline project concept or scope can be related to the complexities and unknowns in the saline ground-water systems found in all source areas. Assessment of the program uncertainties have resulted in reduced salinity impacts and higher cost per unit reduction. In view of the continuing issues involving water rights for evaporation pond disposal and exportation and the technical problems of disposal ponds (costs, need for liners, 346 acceptable leakage), using the collected saline waters for industrial purposes is the only future strategy that satisfies these concerns. However, this strategy increases our dependence on energy deve lopment and the water use plan of private industry. In order to minimize risk, staging or incremental implementation of project features is being used on several units. Staging allows additional time to monitor actual results and minimize investment if certain features are not proved effective. However, by staging portions of projects, the tradeoffs for minimizing risks involve higher final costs, project completion stretchout, and potential project scaledown due to funding constraints and reductions or loss of local water users' support. Recent experience in monitoring the effects of seepage control and collection wells indicates that conclusive evidence, is highly subject to masking by normal events, and several years monitoring may be necessary. SUMMARY We have developed and continue to perfect the state-ofthe-art knowledge in salinity control efforts; therefore, progress is probably commensurate with our ability to utilize current technology. Controlling salinity in the Colorado River Basin has challenged and cont inues to challenge state-of-the-art technology. With new deve lopments and new ideas that we will have explored here this week, we can continue to work together towards controlling the salinity in the Colorado River Basin in the arid West. REFERENCES 1. Public Law , June 24, USC Minute No. 242 of the International Boundary and Water Commission, United States and Mexico, dated August 30, 1973, concluded pursuant to the Treaty of February 3, 1944, between the United States of America and Mexico (TS994). 3. Bureau of Reclamation, Quality of Water, Colorado River Basin, Progress Report No. 11, January Bureau of Reclamation, Status Report, Colorado River Water Quality Improvement Program, January 1983, Denver, Colorado. 5. Bureau of Reclamation, Special Report, Saline Water Use and Disposal Opportunities, September 1981, Denver, Colorado. 347