(308) The Mesa County Colorado Irrigation Audit Program

Abstract

Seven and one-half square miles, or 4864 acres, of the Grand Valley in Western Colorado consists of high water-using landscapes. Overirrigation of Grand Valley soils flushes 580,000 tons of salt into the Colorado River each year. These salts negatively impact plant and animal health throughout the Colorado River basin. Proper watering of lawns can significantly reduce this problem. Correcting problems with a sprinkler irrigation system can reduce water use by an average of 40%. If water use on all 4864 acres was reduced by 40%, a savings of 11,187 acre feet, or over 3.6 billion gallons, of water would result. The annual historical evapotranspiration (ET) rate for the Grand Valley of Western is ≈61 inches; the ET rate during the irrigation season (April through October) is ≈49 inches. Since a typical sprinkler system is ≈70% efficient, in order to apply 49 inches of water to the soil, ≈70 inches of water is required. Irrigation system problems such as improperly spaced heads, sunken heads and heads not adjusted are typically responsible for 40% more water being applied than necessary. In Western Colorado, this equates to an over-application of 28 inches (2.3 acre feet) of water being applied each year. The 2005 Western Colorado irrigation audit problem covering 18.7 acres of turf. Assuming the problems noted were all corrected, a water savings of 43 acre feet, or 14,013,797 gallons, of water resulted. The 2006 audit program will continue this educational and water-saving effort. A grant from the Department of the Interior-Bureau of Reclamation will help fund the 2006 Irrigation Audit project.