The passage of the Taylor Grazing Act in 1934 marked the end of an era in the land policies in the United States in that disposal of the public lands by homesteading was terminated except under rigidly prescribed procedures, and the remaining public lands covering about 175 million acres in the western conterminous states were brought under regulatory authority for grazing use. In 1934 the lands were mostly in a severe state of deterioration as a result of overgrazing and drought. In addition to reducing numbers of livestock using the lands, successive programs of conservation practices were established of which the Soil and Moisture Conservation Program of the Department of the Interior is of particular interest here. The services of the Geological Survey, in an investigational and advisory capacity were enlisted in this program. The work of the Geological Survey has consisted of the collection of hydrologic data, investigations of range-water supplies to facilitate management and provide information for design of structures and land-treatment measures. Appraisal of the effects of treatment practices has also been an important activity. Conservation on the public domain involves mainly growing vegetation for forage and reducing erosion. The two elements are intimately related--accomplishment in one is usually reflected by an improvement in the other. Erosion is a serious problem on most of the public domain, but particularly in the Colorado River and Rio Grande basins where, despite low annual water yields, the public domain and similar lands on the Indian reservations contribute the major part of the sediment measured at the downstream gaging stations. In parts of the Missouri River basin also, erosion is obviously very active but the sediment yield contributed by the public domain cannot be as readily isolated. The reasons for the erosion are generally evident--the erodibility of the rock and soils and the sparsity of vegetation as a result of low precipitation, unfavorable soils, or past land use. How much is due to the land use is still controversial, resulting in many questions relative to planning corrective measures. The problem facing the early administrators of the Taylor Grazing Act to bring about proper use and conservation of the public domain was a difficult one because of the lack of records on actual grazing use in animal-unit months of the qualified allottees and the lack of data on treatment practices in an arid area. Reduction of grazing was imperative in some localities, but generally, it could not be brought about as rapidly as it should have been. Numbers of animal units in the grazing districts were reduced from about 3.6 million in 1941 to about 3.2 million in 1964, whereas the areas included in districts was increased about 3 percent. Reductions are still being made in certain areas where deterioration is evident. One of the earliest activities connected with management of the range was the development of water supplies to facilitate the distribution of grazing. The investigations needed for such development formed a large part of the early work in the Soil and Moisture program of the Geological Survey and has continued to be a major activity to the present time. Most of the work has involved investigations of sites for wells but has included also the investigation of proposed spring developments and collection of hydrologic data for use in reservoir design. Well-site investigations have been of two general types: (1) the investigation of a site selected by the land administration agency, and (2) an areal investigation covering entire grazing districts or units thereof. In each type of investigation, a study is made of the geology and the recharge conditions. Reports are prepared giving estimates of the depth of drilling required, the depth to water, the yield, and the quality of the water, together with other information on drilling conditions and developing. Springs are a significant so