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r 0011060 . 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 and the Minute 242 treaty obligations to Mexico. The two requirements, one estab- lished by the basin states and the other by a treaty with Mexico, are separate and distinct. 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 salinity of no more than TDS of 115 + 30 ppm over the annual average salinity of Colorado River waters which arrives at Imperial Dam. In order to maintain the differential TDS of 115 + 30 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 We1lton-Mohawk irri- gation return flows in order to maintain the established differential TDS under future river conditions. In additfon, the water recovered by the Yuma desalting complex and related Title I features are expected to replace a portion of the waters now used from storage for the ongoing bypass of Wellton-Mohawk flows. 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 predict- ing future river conditions and establishing operational parameters for the plant, a modular plant design was selected to provide additional flexibility to the system. , , 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 regard- ing 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 necessity, 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 operations, the long-term salinity reduction potential may be constrained by different operational scenarios. We may not select the applicable operational regime for salinity control through lack of knowledge of the overall effects. 2