Water quality of the North Platte River, east-central Wyoming

This report is a statistical summary of 40 different constituents and physical characteristics that describe the water quality of the North Platter River between Alcova Dam and Orin, Wyoming, a distance of 143 river miles. Data from seven stations are summarized for 1970-79. Water entering the North Platte River upstream from Casper generally is more mineralized and degraded than the water in the North Platte River or in the tributaries entering the river downstream from Casper. The average dissolved solids concentration was about 320 mg/L at the upper sampling station and about 430 mg/L just downstream from Casper. This increase is typical of many other constituents. The mean fecal-coliform concentration at the upper station was about 8 colonies/ml and about 4,000 colonies/100 ml at the station downstream from Casper. Concentrations of some constituents periodically were greater than maximum recommended for drinking water supplies. About 24% of the dissolved solids concentrations were more than 500 mg/L. Some selenium concentrations exceeded the limit of 10 micrograms/L mandated for public water supplies. Large concentrations of copper, zinc, and ammonia indicate that these constituents might be a problem for sensitive aquatic life. (USGS)