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Analysis of Escherichia coli, total recoverable iron, and dissolved selenium concentrations and loads for 303(d) listed segments in the Grand Valley, Colorado, 1991-2018

March 2, 2020

The U.S. Geological Survey, in cooperation with Grand Valley Drainage District, Colorado Water Conservation Board, Colorado Department of Public Health and Environment, and Colorado River Water Conservation District, conducted a loading analysis for selected constituents and tributaries in the Grand Valley, Colorado, to support the development of total maximum daily loads (TMDL) at monitoring locations on U.S. Environmental Protection Agency 303(d) listed segments. The data tables include Escherichia coli, total recoverable iron, and dissolved selenium concentrations, streamflow data, and computed loads as well as dissolved selenium regression model diagnostics and results. Concentration and streamflow data were compiled from the Water Quality Portal with data from the U.S. Geological Survey, Colorado Department of Public Health and Environment, and Colorado Riverwatch. Tables include monitoring location identification information, data collection time frames, concentration data, as well as calculations of means, medians, select percentiles, and percent reduction in loads to meet state regulatory standards for computed loads during both irrigation and non-irrigation seasons.