In 1982-84, a water resources appraisal of Owens Valley was made by using available hydrologic information. Results of the appraisal provided an overview of water resources in Owens Valley; a better understanding of the groundwater system; and a framework for additional studies. Owens Valley is in east-central California and is the major source of water supply for the city of Los Angeles, located 233 mi to the south. Since 1913, with the completion of the first aqueduct, surface water has been diverted from the Owens River to Los Angeles. In 1970, a second Aqueduct was completed. Groundwater pumping was increased to supplement the water needed for the increasing population in Los Angeles. Most of the outflow of water from Owens Valley is from exports via the aqueduct system and by evapotranspiration loss; principal sources of water are runoff, inflow from Pleasant Valley Reservoir, and precipitation. Streamflow from the Sierra Nevada is a source of tremendous quantities of water to the valley. Pumping from more than 90 pump-equipped wells averaged about 98,000 acre-ft/yr from 1971 to 1983, but it was generally < 10,000 acre-ft/yr from 1932 to 1970, except during dry years. Groundwater pumping is primarily from deep wells adjacent to the volcanic rocks near Big Pine. Wells completed in the volcanic rocks yield large quantities of groundwater. Water level fluctuations in deep wells indicate a direct correlation with groundwater pumpage. Fluctuations in shallow wells are affected not only by pumping, but also by evapotranspiration and precipitation. The cause-and-effect relation of water level fluctuations in deep and shallow wells is not well understood and is partly the subject of a 5-yr study currently being conducted by Inyo County, the city of Los Angeles, and the U.S. Geological Survey, which emphasizes: (1) vegetation, (2) plant survivability, and (3) groundwater. It is hoped that this study will better define the quantity and availability of groundwater in the valley, as well as determine the effects of groundwater withdrawals on native vegetation. (Lantz-PTT)