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Reconnaissance appraisals.-- Reconnaissance appraisals are proposed for those ground-water basins that have not been developed or investigated, to estimate or determine extent and properties of the aquifers and chemical quality of the water, to define sources of recharge, and to estimate storage capability and yield. Some such basins doubtless contain water of good quality and appreciable quantity. Other basins are known to, or may, contain brackish water that would be unusable unless diluted. To take full advantage of new developments in the technology of desalination, the brackish-water bodies would be delineated so far as is feasible. The reconnaissance appraisals must be based on extensive knowledge of the areal geology; readily available hydrologic information would be gathered also. They are proposed to be largely completed within ten years. Estimated cost, first year $100,000, second to fifth year $250,000 per year. Managed storage.-- In certain ground-water reservoirs, storage space can be evacuated by withdrawing water seasonally or during a succession of drought years, and then refilled from surplus streamflow either naturally or artificially. Under favorable circumstances, it should be practical to manage underground storage so that perennial water yield would be increased. Oversimplified, this is a principal method by which surface- and ground-water sources may be managed jointly. Determining potentials for such management would be an integral part of the potential-yield and reconnaissance appraisals described above. Major opportunities for managed underground storage appear to exist beneath the valley plain along the main stem of the Colorado River. In particular, a terminal-storage facility of this kind in the vicinity of Yuma, with manageable storage capacity of 500,000 to 1,000,000 acre-feet, may prove feasible and practical. Appraisal of the physical and hydrologic features related to this potential is one objective of the Lower Colorado River investigation currently under way. Surface-Water Sources Gaging-station network.-- Over most of the Pacific Southwest, the network of primary gaging stations on principal streams is reasonably adequate. Ultimately, however, a moderate number of roving, secondary stations will be useful to: (1) discriminate uncommitted supplies that may prove to be developable in the Little Colorado and Bill Williams river basins and elsewhere at scattered places; and (2) determine magnitude and frequency of ephemeral discharge into numerous desert basins, discharge which is a principal source of ground-water recharge. It is proposed that, in each year of an initial five-year period, 50 secondary stations be established; also that each year thereafter, 50 such stations be relocated to new sites. Cost, first year $50,000, second to fifth year $140,000 per year. 8Epson Perfection 4870 Photo, 400 dpi, 8 bit, 14,004,224 byte