Future Quantity and Quality of Colorado River Water

Depletions of the natural flow of Colorado River by future upstream developments will have little effect on the total salt burden but a pronounced effect on the unit concentration of salts in the water available for use in the Lower Basin and Mexico. By 1995 the supply available for such use will shrink from an average of 11,800,000 to 8,000,000 acre-ft per yr and the concentration of salts at Lake Havasu will progressively increase from 10.75 milligram equivalents per liter (mel)(655 ppm) to approximately 15.0 mel (926 ppm). Future trans-mountain diversion, irrigation projects, domestic and industrial developments, and reservoirs will each have certain effects on the final composition of the dissolved salts. It is probable that the reacting value (relative concentration of anions or cations measured in mel) of calcium will decrease from 40.5% to 38.6% and magnesium from 21.1% to 20.9% with a corresponding increase in sodium plus potassium from 38.4% to 40.5%. The reacting value of bicarbonate is expected to decrease from 23.4% to 18.4% with sulphate increasing from 56.4% to 60.1% and chloride plus nitrate increasing from 20.2% to 21.5%.