Skip to main content
U.S. flag

An official website of the United States government

Substantial declines in salinity observed across the Upper Colorado River Basin during the 20th century, 1929 to 2019

April 19, 2021

Salinity in the Colorado River Basin causes an estimated $300 to $400 million per year in economic damages in the U.S. To inform and improve salinity‐control efforts, this study quantifies long‐term trends in salinity (dissolved solids) across the Upper Colorado River Basin (UCRB), including time periods prior to the construction of large dams and preceding the implementation of salinity‐control projects. Weighted Regressions on Time, Discharge, and Season was used with datasets of dissolved‐solids and specific‐conductance measurements, collected as early as 1929, to evaluate long‐term trends in dissolved‐solids loads and concentrations in streams from 1929 to 2019 (n=14). Results indicate that large, widespread, and sustained downward trends in dissolved‐solids concentrations and loads occurred over the last 50 to 90 years. For 12 of the 14 stream sites with significant downward change, median declines of ‐38% (range of ‐14 to ‐57%) and ‐40% (range of ‐9 to ‐65%) were observed for flow‐normalized concentration and load, respectively. Steepest rates of decline occurred from 1980 to 2000, coincident with the initiation of salinity‐control efforts in the 1980s. However, there was a consistent slowing or reversing of downward trends after 2000 even though salinity‐control efforts continued. Significant decreases in salinity occurred as early as the 1940s at some streams, indicating that, in addition to salinity‐control projects, changes in land cover, land use, and/or climate substantially affect salinity transport in the UCRB. Observed dissolved‐solids trends are likely the result of changes to watershed‐related processes, not due to changes in the streamflow regime.

Publication Year 2021
Title Substantial declines in salinity observed across the Upper Colorado River Basin during the 20th century, 1929 to 2019
DOI 10.1029/2020WR028581
Authors Christine Rumsey, Olivia L. Miller, Robert Hirsch, Thomas M. Marston, David Susong
Publication Type Article
Publication Subtype Journal Article
Series Title Water Resources Research
Index ID 70220266
Record Source USGS Publications Warehouse
USGS Organization Utah Water Science Center
Was this page helpful?