The U.S. Geological Survey (USGS), in cooperation with the Grand Valley Drainage District and the Colorado Water Conservation Board, conducted a loading analysis for selected constituents and tributaries to the Colorado River in the Grand Valley, western Colorado, using data from 1991 to 2018, to characterize concentrations, stream loading, and load reductions for Escherichia coli, total recoverable iron, and dissolved selenium for stream segments on the State of Colorado 303(d) list of impaired waters. Escherichia coli, total recoverable iron, and dissolved selenium concentrations and streamflow data were compiled from the Water Quality Portal (WQP). The data tables include information on sites, data collection time periods, concentrations, computed loads, and regression model diagnostics. Dissolved selenium annual loads, percentage load reductions required to meet State regulatory standards, mean daily loads computed for irrigation and nonirrigation seasons, and regression model diagnostics and results are presented for sites where sufficient data were available.
First posted February 2020
Revised August 2020, version 2.0