2003 - Laserfiche WebLink

Home Browse Search

e SUMMARY The Quality of Water Progress Report for the Colorado River Basin is prepared and updated every 2 years to summarize the status of water quality in the Colorado River Basin. Although several water quality parameters are reviewed, salinity is by far the most serious and is allotted a major portion of this report. The report summarizes the pastt present, and future projected salinities at various stations in the basin; discusses the causes of salinity; summarizes the development of the water supply of the basin and its impact on salinity; reviews the salinity control program; and summarizes special studies related to water quality in the basin. e Extremely high flows in the Colorado River, two to three times nor- mal, have reduced salinity to its lowest level in 30 years. All of the main stem reservoirs were flushed by these high flows and now have in storage water with unusually low salinities. According to the latest salinity projections, the numeric criteria at Imperial Dam will be satis- fied until 1993 by the salinity control units already in operation. Development in the basin, which reduces the flow of the river and its ability to dilute salinity, is projected to increase water depletions from 9.6 million acre-feet per year in 1983 to 12.8 million acre-feet per year by 20l0. To maintain the numeric salinity criteria of 879 milligrams per liter (mg/L) at Imperial Dam, a l.S-million-ton salt load reduction will be necessary to compensate for the development of this water. Nutrient loading to the main stem reservoirs is becoming a problem as development and its associated pollution increase. Increases in phosphorus and nitrogen compounds which are essential to the growth of algae, the base of the food chain in reservoirs, are causing some por- tions of the reservoirs to become eutrophic (overly productive). Eutrophication of reservoirs can impair municipalt industrial, and recreational uses by causing taste and odor problems, creating toxins, and reducing the dissolved oxygen available for fish. While nutrients in some reservoirs are causing them to become eutrophic, reservoirs further downstream are becoming nutrient poor due to the trapping of nutrients in the upstream reservoirs. This has the effect of reduc- ing the productivity of the fisheries by limiting their food supply. Studies are described which help define and resolve some of these problems in the Colorado River Basin. e