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. . 0022S0 Special emphasis is placed on two of the current-program items: the bydrolog:l.creg1men of the lower Colorado River basin and the arid- zone research. ~ese two, include in'lestigations of the intensive, particularbed type needed as the basis for future water-me.lie.gement decisions. Work on the regimen of the lower Colorado River basin (fig. 2, area I) began in 1960; it is scheduled to continue at least through 1965. Included are the drainage area of the main-stem river belOW Davis Il8m and the IJDperial Valley (Salton Sea); excluded are the tributary valleys of the Bill Williams and Gila rivers. Particular attention is being paid to (1) the balance mong precipitation, evaporation lIJld consumptive use, and runoff; (2) storage, movement, and chemical character of ground water, including international aspects I (3) extent and properties of the ground-water aquifers, and their relation to the river; and (4) water budget of the Salton Sea, including accurate measurements of inflow and independent measurements of evapora- tion. ~e consumptive-use studies include evapotranspirometer tanks near Yuma, Arizona, operated in cooperation with the Bureau of Rec18lllll.- tion. Reports on certain ear~ phases of the work are in preparation. A general purpose of the work is to define alternative water-management steps that are possible and to' appraise the potential effects of each such step. The arid-zone research concerns (1) water consumption by phreatopbytes, chief~ saltcedar, as measured in evapotranspirometer tanks at Buckeye, Arizona (in collaboration between the Geological Survey and the Bureau of Reclamation), (2) potential for water salvage by eradicating riparian vegetation in the Gila River valley above San Carlos Reservoir; (3) hydrologic e:f'fects of replacing juniper and piI\YOll pine with grasses in the Carrizo and Corduroy Creek basins near SI1owlow, Arizona; (4) soil-moisture chemistry and energy relationships in an area of riparian vegetation; (5) theory and measurement of evapotranspiration; (6) mass transfer of moisture in the atmosphere, measured by airborne equipment; and (7) thunderstorm patterns and rain- fall in relation to runoff on the arid plains of southern Arizona, in part measured by radar. Digital-punch recording equipment and an unique electric-analog 'computer are used as appropriate. 6