Available from the U.S. Geological Survey, Branch of Information Services, Box 25286, Denver Federal Center, Denver, CO 80225, USGS Water-Resources Investigations Report 01-4204, 14 p., 5 figs.
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Selenium and salinity are water-quality issues in the Upper Colorado
River Basin. Certain water bodies in the lower Gunnison River Basin, including
the lower Gunnison River and the Uncompahgre River, exceed the State standard
for selenium of 5 micrograms per liter. Remediation methods to reduce
selenium and salt loading in the lower Gunnison River Basin were examined.
A demonstration project in Montrose Arroyo, located in the Uncompahgre
River Basin near Montrose, was done during 1998-2000 to determine the
effects on selenium and salt loads in Montrose Arroyo from replacing 8.5
miles of open-ditch irrigation laterals with 7.5 miles of pipe. The participants
in the project were the National Irrigation Water Quality Program, the
Colorado River Basin Salinity Control Program, the Uncompahgre Valley
Water Users Association, and the U.S. Geological Survey.
The placing of five laterals in pipe significantly decreased selenium
loads in Montrose Arroyo. The selenium load at the outflow monitoring
site was about 194 pounds per year less (28-percent decrease) in the period
after the laterals were placed in pipe. More than 90 percent of the decrease
in selenium load was attributed to a decrease in ground-water load.
Salt loads also decreased because of the lateral project, but by a smaller
percentage than the selenium loads. The salt load at the outflow site
on Montrose Arroyo was about 1,980 tons per year less in the post-project
period than in the pre-project period.
All of the effects of the demonstration project on selenium and salt loads probably were not measured by this study because some of the lateral leakage that was eliminated had not necessarily discharged to Montrose Arroyo upstream from the monitoring sites. A greater decrease in selenium loads relative to salt loads may have been partially the result of decreases in selenium concentrations in ground water in some areas.
Montrose Arroyo Demonstration Project
Monitoring Program and Method of Analysis
Effects of Project on Selenium and Salt Loads
Factors Affecting Selenium and Salt Loads
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