Dissolved-solids loads increased from 1986 to 1988 at nine streamflow water-quality stations on the upper Colorado River and its tributaries between Lake J.B. Thomas and O.H. Ivie Reservoir. About 51 percent of the dissolved-solids load to E.V. Spence Reservoir resulted from saline-water outflow from Natural Dam Salt Lake on Beals Creek. The concen- tration of dissolved solids in streamflow generally decreased in the downstream direction as flows increased in all reaches of the river and its tributaries. The estimated disolved-solids concen- tration exceeded 1,000 milligrams per liter for water from about 233 of 386 wells and springs for which specific conductance was measured in 1986. The mean concentration for all wells was about 1,750 milligrams per liter. Mixing with brine associated with oil and gas producton is a major process affecting the salinity of streamflow and shallow-aquifer water. Dissolution of gypsum and pyrite contributed to salinity of water in shallow aquifers because of the presence of these minerals in most formations. Some salinity in streamflow and shallow-aquifer water was attributed to evapotranspiration in areas where water was close to land surface, in irrigated areas, and along streams. Dissolution of halite or mixing with deep-aquifer water was the most common cause of increased salinity in water samples from shallow aquifers as classified using salt-norm analysis. Mixing with water from soil-mineral dissolution was classified as the principal source of chloride in water samples from shallow aquifers with nitrate determinations. Trace species/chloride ratios indicated that mixing with water from deep aquifers in rocks of the Pennsylvanian System was the principal source of chloride in 24.4 percent of 45 shallow-aquifer samples lacking nitrate determinatoins.
Additional Publication Details
USGS Numbered Series
Characteristics of streams and aquifers and processes affecting the salinity of water in the upper Colorado River basin, Texas
Water-Resources Investigations Report
U.S. Geological Survey ;
USGS Earth Science Information Center, Open-File Reports Section [distributor],