Surface water-quality characteristics in the upper North Fork Gunnison River basin, Colorado

Analyses of water quality data collected during 1982 and 1983 in the upper North Fork Gunnison River basin indicate that dissolved-solids concentrations are relatively small, with a mean value near 97 milligrams per liter. Most major dissolved constituents also had small measured concentrations throughout the study area. Trace-element concentrations generally were small; however, total-iron concentration generally was large in the area with a mean concentration of about 8,250 micrograms per liter. The cause of this larger iron concentration probably is related to the local geology. Paonia Reservoir, located on Muddy Creek, greatly reduced suspended-sediment and trace-element concentrations. The reservoir had only a slight effect on major dissolved-constituent concentrations. Analyses of alkalinity, sulfate, and dissolved-solids concentrations indicated that little, if any, changes in water quality occur as a result of coal mining; however, more data are needed to make more definite conclusions. Sulfate concentrations increased slightly downstream through the mined area; however, with the small concentrations measured and limited quantity of data, the source of the increased sulfate could not be determined. (USGS)