Ground-water quality along the Mojave River near Barstow, California, 1974-79

The quality of ground water in the alluvium along the usually dry Mojave River near Barstow, Calif., has been monitored since 1974. Degradation has occurred as a result of wastewater discharge and irrigation return. Characteristics of the degraded ground water include concentrations of dissolved solids exceeding 1,000 milligrams per liter, odor threshold numbers exceeding 5, dissolved organic carbon exceeding 2.0 milligrams per liter, chloride exceeding 250 milligrams per liter, phenols exceeding 1 microgram per liter, and methylene blue active substances exceeding 0.20 milligram per liter. Large flows in the river during the winters of 1977-78 and 1978-79 recharged the aquifer with water from storm runoff. The ground-water-quality monitoring data showed that few changes in the concentration and distribution of chemical constituents occurred between 1974 and 1977, but between 1977 and 1979 there were overall decreases in most constituents and in odor. The monitoring data also showed that between 1977 and 1979 the degraded ground water spread and moved downgradient, whereas prior to 1977 it had been generally confined to an area between Barstow and the U.S. Marine Corps Supply Center. (USGS)