Water-quality data collected during 1973-77 for hydrologic studies in the northern Powder River Basin of southeastern Montana provide a data base for shallow ground water. The 665 water samples collected were analyzed for major cations and anions. Of the samples, 516 were from wells and 149 were from springs. About 10 percent of the samples were also analyzed for trace constituents and radiochemistry. The majority of analyses were performed by the Montana Bureau of Mines and Geology laboratory

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... n Butte, Montana. The remaining analyses, including all trace constituent and radiochemical analyses, were performed by the USGS National Water Quality Laboratory in Denver, Colorado. 47C 108°107°4 6C 45C 106°~~105°~ MONTANA V^-LL ocation of study area POWDER RIVER J ^o >