A set of four adjoining 7.5-minute quadrangle sheets that together depict the upper Mongaup River Basin in Sullivan County , N.Y., at 1:24,000 scale show the location, well yield, depth, water use, ownership, and date of ownership of wells, test holes , and springs. Most wells that tap stratified-drift deposits have high yields (50 to 300 gal/min) and are used for public supply. Bedrock wells have smaller yields and are generally used for domestic supply. The data were compiled from a previous U.S. Geological Survey, countywide, groundwater resources report and from unpublished data. (USGS)