Coalbed methane development in the Powder River Basin has been increasing in recent years, and with it the discharge of co-produced sodium bicarbonate water. Coproduced water is disposed of via evaporation or infiltration reservoirs, Imation spreading, livestock watering, and direct discharge into draws and rivers. The objective of this study was to determine if trend analyses could identify or quantify significant changes in Little Powder River sodium concentration and sodium adsorption ratio, and which might be coincident with coalbed methane co-produced water reaching the main channel of the River. Various parametric and nonparametric statistical analyses were conducted on a time series of existing U. S. Geological Survey data for the Little Powder River above Dry Creek near Weston, Wyoming (USGS site 06324970). Based on the varied results from this study, it is difficult to conclude whether or not coalbed methane co-produced water is reaching the Little Powder River and thereby altering the chemistry of the water.