Statistical summary of the chemical quality of surface water in the Powder River coal basin, the Hanna coal field, and the Green River coal region, Wyoming

A summary of the chemical quality of surface water in the three principal coal-producing areas of Wyoming was intensified by the U.S. Geologic Survey during 1975-81, in response to interest spurred by a dramatic increase in surface mining of the areas. This statistical summary consists of descriptive statistics and regression analyses of data from 72 stations on streams in the Powder River coal basin, the Hanna coal field, and the Green River coal region of Wyoming. The mean dissolved-solids concentrations in streams ranged from 15 to 4,800 mg/L. Samples collected near mountainous areas or in the upstream reaches of perennial streams in the plains had the smallest concentrations of dissolved solids, and the predominant ions were calcium and bicarbonate. Samples from ephemeral, intermittent, and the downstream reaches of perennial streams in the plains contained relatively large dissolved-solids concentrations, and the predominant ions usually were sodium and sulfate. Regression models showed that the concentrations of dissolved solids, calcium, magnesium, sodium, alkalinity, sulfate, and chloride correlated well with specific-conductance values in many of the streams. (USGS)