, and charged with the responsibility for "Classification of the public lands and examination of the geological structure, mineral resources, and products of the national domain." In 1894, a small appropriation was obtained for the specific purpose of "gauging streams and determining the water supply of the United States." Subsequently, the role of the Geological Survey in water resources gradually expanded and the Survey now has the principal responsibility for appraising the source, quantity, quality, and movement of the Nation's water resources. In addition, it is the lead agency for coordinating the activities of all Federal agencies in the acquisition of water data on streams, lakes, reservoirs, estuaries, and ground waters. WATER RESOURCES DIVISION The mission of the Water Resources Division is to provide the hydro!ogic information and understanding needed for the optimum utilization and management of the Nation's water resources for the overall benefit of the people of the United States. This is accomplished, in large part, through cooperation with other Federal and non-Federal agencies, by: 1. Collecting, on a systematic basis, data needed for the continuing determination and evaluation of the quantity, quality, and use of the Nation's water resources. 2. Conducting analytical and interpretative water-resource appraisals describing the occurrence, availability, and physical, chemical, and biological characteristics of surface and ground water. ORGANIZATION This bibliography contains four lists of the publications. They are organized according to criteria that reflect the variable needs and information bases available to potential users of the bibliography.