This report about the water resources of the Curlew Valley drain- age basin, Utah and Idaho, was prepared by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Wildlife Resources. The primary purpose of the study on which this re- port is based was to determine whether or not the flow of Locomotive Springs--a source of water for a State Waterfowl Management Area--has been or will be diminished as a result of ground-water withdrawals elsewhere in Curlew Valley. To this end, it was necessary to make a quantitative appraisal of the water resources of the Curlew Valley drainage basin, with emphasis on ground water, and to evaluate the effects of both present and planned water-supply developments on the hydrologic regimen.