An accounting system for estimating and distributing consumptive use of water by vegetation to water users was developed for the Colorado River to meet the requirements of a U.S. Supreme Court decree and used with data from calendar year 1984. The system is based on a water-budget method to estimate total consumptive use by vegetation which is apportioned to agricultural users by using percentages of total evapotranspiration by vegetation estimated from digital-image analysis of satellite data.