An estimate of watershed efficiency for a Colorado alpine basin

A two year project was conducted during 1973 and 1974 in a 3 sq km alpine basin located tweny miles west of Boulder in the city's watershed. The spring snow survey taken at peak accumulation indicated that 67 cm of snow water equivalent was held on the basin. subsequent ablation measurements revealed that slopes with a southern aspect contributed most per unit area to stream discharge. Stream stage was recorded at two locations within the basin from May until the end of september. Annual discharge from the basin was estimated to be 2.15 * 10(6)m(3), enough to fulfull the treated water requirement of boulder City for approximately two months. A water budget for the basin was established in terms of generated discharge, precipitation, and evapotranspiration. From the water budget, watershed efficiency (output expressed as a percentage of input) was estimated to be in excess of 90%. This estimage is in agreement with that other workers have found for watershed efficiencies in the Rocky Mountain alpine zone. Partially as a result of the high watershed efficiencies found in alpine areas, it has been suggested that these areas might be used to increase water supply to populated areas of the Western United States.