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, 002555 . . _,I , (t( /) ';;;',0 !7<. '--' , /~,n, ( r~ ~J+. ~1~~~~ ~"'.e tQ(O 0 1,9 ~ "~k9 . ~f),; 52 ',I'jl!! <<-., , ~. " ..." .>~ UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY SUMMARY OF ACTIVITIES IN THE PACIFIC SOUTHWEST JANUARY-JUNE 1962 This report highlights investigations and research Survey in land classification, geology, water, and Pacific Southwest from January through June 1962. Survey's continuing operations are not covered. ,,' by the Geological. topography in the Many of the '.-,;:;-/ Water-Resources Investigations Special studies,- First steps have been taken toward a water-budget analysis to determine the change in evapotranspiration that may be effected by removing native phreatophytes and substituting a useful plant species such as Bermuda grass. The study area is the 16-mile reach of Gila River flood plain on the San Carlos Indian Reservation, between the highway bridge on U. S. Route 70 and a point about 2 miles upstream from the confluence with the San Carlos River. In this reach, phreatophytes cover some 5,000 acres. The reach will be divided into three segments; for each of these segments the water budget will discriminate precipitation on the flood plain, inflow and outflow of surface water and ground water, and change in ground-water and soil-water storage. The project schedule is to complete instru- mentation by early 1963, complete pre-calibration in 1966. replace the native plants by suitable species in 1967, and evaluate evapo- transpiration by the replacing species from 1968 to 1970. Evapotran- spiration by the individual plant species will be evaluated from 10- acre plots. Two such plots--for cottonwood and for mesquite--have been selected on the flood plain of the San Carlos River. In the field of soil-and-moisture conservation, the broad-scale in- vestigation of the Winnemucca Grazing District (Humboldt and Pershing Counties, Nevada) was completed and the technical report covering the study is in final review status. A report on water-supply ex- ploration in the Pyramid Grazing District, Nevada, is essentially completed. Field phases of water-supply conditions in the Carson City Grazing District are nearing completion. The latter two districts cover about 41,500 square miles in the northwest part of the State. The Survey continued the intensive water-resource studies in the reach of the Humboldt River near Winnemucca,Nevada, as a segment of the inter-agency Humboldt River Research Project, Evapotranspiration studies were accelerated during the period through completion of planting in the plastic membrane tanks for determining consumptive use of variou~ phreatophytes. Several reports on the project findings were released to the open file, including the preliminary results of the hydro-geologic investigations in the study area.