The Joliet-Fromberg coal tract in Carbon County, Montana, contains subbituminous to bituminous coal suitable for underground mining. A reconnaissance study of the area was conducted to identify water resources of the coal tract and to determine general effects that underground mining could have on the water resources. Surface-water resources consist of Elbow Creek, a small perennial stream that drains most of the area, plus irrigation water diverted into the basin from Rock Creek and the Clarks Fork Yellowstone River. Groundwater resources consist of sandstone aquifers in several formations of Late Cretaceous age and alluvial aquifers of Pleistocene and Holocene age. Chemical analyses were made of water in Elbow Creek and water from seven wells in the area. Water from Elbow Creek is suitable for use by all livestock, based on the concentration of dissolved solids. Water from most sampled wells had dissolved-solids concentrations larger than the maximum (500 milligrams/L) recommended by the U.S. Environmental Protection Agency for public water supply. Effects of underground mining on water resources would be minimal. The Bridger coal bed in the Upper Cretaceous Eagle Sandstone has no significant hydraulic connection with Elbow Creek in most of the area and the Bridger coal bed does not appear to be a significant aquifer. Mining and dewatering of the coal could temporarily lower water levels in aquifers overlying the coal if mining causes subsidence and fracturing of rocks above the mine workings. (USGS)