Arizona Water Resource Volume 11 Number 4

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2 Arizona Water Resource May - June 2003 Desalination... continued from page 1 landlocked Arizona will not be desalinating seawater. The value of inland brackish water as a water supply is being increasingly rec- ognized. It is a resource that previously had been overlooked since other higher- quality, more potable water supplies were available. With supplies of such waters now more limited brackish water is attracting attention as a potential drinking water source. It is Arizona's involvement in the poli- tics of salinity at the international level that distinguishes the state's situation. In this are- na, Arizona's involvement with salinity and salinity control predates the current interest. Through its participation in the Colorado River Basin Salinity Control Forum Arizona has been active in desalination strategies since 1975. The seven basin states created the fo- rum in response to the political crisis arising when Mexico objected to the salinity levels of the Colorado River as its waters entered the country. The forum's intent was to reduce salinity and recommend water qual- ity standards for various points along the Colorado River. The issue was water qual- ity, and the goal was to reduce the amount of salt entering the river from the upper basin states. Strategies included encouraging on -farm irrigation efficiencies to control salinity and taking measure to prevent saline groundwater from entering the river. Recently Arizona's interest in the Colo- rado River salinity issue has acquired a new focus due to its concern about ensuring the state's supply of Colorado River water. Un- like other areas of the country where new desalination plants are being proposed, at issue in Arizona is the operation of a plant that was constructed over ten years ago. The state is urging the U.S. Bureau of Reclama- tion to put the Yuma desalination plant on line. To Arizona, desalination in this situa- tion is a water supply issue. The plant was constructed to reclaim drainage water from the Wellton- Mohawk Irrigation District, to ensure that water de- livered to Mexico is suitable for beneficial use. Per treaty obligation, the United States is to ensure delivery of 1,500,000 acre -feet of water each year. Drainage from the ir- ritation district averages more than 100,000 acre -feet per year which, because of its high salinity, was unsuitable for delivery to Mexico. In what was to be a temporary solution to the problem, drainage water was bypassed around the Mexican diversion at Morelos Dam, with the 100,000 acre -feet not figuring into the Mexican Colorado River allocation. That the wastewater was being by- passed was not a critical issue at one time since there were abundant flows on the Colorado River during most of the 1990s, and the Lower Basin States were not using their full 7.5 million acre -feet allocation. Operation of the plant therefore, which was completed in 1992, was not critical. Times have changed, however, with water supplies back to normal and lower basin states' water demands in excess of compact apportion- ments. Meanwhile the upper basin demands continue to grow. Arizona argues that the bypassed water is in a sense a lost opportunity, its flows not credited as part of Mexico's entitlement. It says that delivery of water in excess of trea- ty requirements will result in an increased frequency of water supply shortages in the United States. Arizona water users stand to be hurt the most since the Central Arizona Project is junior to all other water users in the Lower Basin. The federal government is balking at starting up the plant, offering instead to retire Arizona and California farmland to free up additional water supplies. Arizona doubts this a workable strategy and is urg- ing the operation of the plant. This is a very controversial issue since the bypassed water has environmental value in maintaining the Cienga de Santa Clara in Mexico. If the plant were operating, the reduced wastewa- ter then flowing to the cenga would greatly increase in salinity, posing a threat to the wetlands. While desalination of Colorado River water is debated officials in central Arizona are pondering their salinity concerns and the possible role of desalination. The area is plagued by a salt loading problem, with the diversion and use of surface water resulting in an accumulation of salts. Phoenix area water officials have organized the Central Arizona Salinity Study to investigate the worsening problem. Steve Rossi, the principal water re- sources planner for the City of Phoenix, says phase one of the study has been an Continued on page 12