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I I I I I I I I I I I I I I I J I I I storage of providing additional releases, in lieu of using WHIDD drainage return flow, to meet the 1944 Treaty with Hexico during an indeterminate interim period. At the time of authorization, it was intended that the water savings resulting from the canal lining would be available as a replacement water supply while the Desalting Plant was under construction. Further, the 1914 Act recognized that the conserved water ultimately belonged to water users in California and would only be available to the United States as long as water demand in the Lower Basin was less than the 1.5 million af apportioned for annual use during nomal water supply years. The 1914 Act, therefore, provided that the interim period would end when California's requested water supplies were unable to be satisfied because use in the Lower Basin had reached its maximum annual apportionment. Since water utilization by the Central Arizona Project has not developed as projected and reservoir storage conditions are such that the reservoir system is likely to refill in the near-term, the United States continues to be able to meet California water requests. It appears, therefore, that the interim period will continue for the next few years and possibly longer. The PRPU was constructed to manage and conserve ground water for the United States and for meeting part of the annual water delivery requirement for Hexico. Under the terms of the 1944 Treaty, approximately 140,000 af of Hexico's 1.5 million acre-foot entitlement can be delivered at the Southerly International Boundary with Hexico. Currently, approximately 100,000 af of this amount comes from wasteways (drainage flows) in the Yuma Valley of Arizona, and 40,000 af comes from the PRPU. Because flows from the wasteways have been greater than anticipated, only 21 of the 35 wells authorized by the 1914 Act have been installed and are under operation. If flows from the wasteways decline, additional wells will have to be installed. Due to the unexpected time required for construction, flows of the bypassed WHIDD irrigation drainage expanded the Santa Clara Slough (Slough) from a relatively small area to several thousand acres of aquatic and wetland environment. Two of the United States Federally endangered species, the Yuma Clapper Rail bird and the Desert Pupfish, occur in the marsh. There is concern that when the Desalting Plant begins operation, the resulting combination of reduced flows plus increased salinity will adversely impact the Slough and its associated species. In cooperation with the United States Fish and Wildlife Service, Reclamation asked the United States Section of the International Boundary and Water Commission to approach the country of Hexico to see if studies could be conducted to determine what impacts, if any, might be expected as a result of Desalting Plant operation. As a result, the United States and Hexico have initiated a coordinated effort to collect baseline environmental data on the Slough. ALTERNATIVES Five basic alternatives for operation of the Desalting Plant were evaluated for the interim period. The five basic alternatives include: (A) Shutdown the Desalting Plant and, after the interim period, use releases from storage to meet the 1944 Treaty deliveries; (B) 00 not operate the Desalting Plant and, after the interim period, activate the Desalting Plant; (C) Operate the Desalting Plant at partial capacity during the interim period; (0) 00 Not Hi