Using Landsat thermal imagery with the Mapping Evapotranspiration at High Resolution and Internalized Calibration (METRIC) procedure, consumptive water use of irrigated and non-irrigated lands was estimated at 30-m resolution in the Klamath Basin, Oregon. Because ground surfaces with large ET rates are cooler than ground surfaces that have less ET, irrigated fields appear on images as being cooler than nonirrigated fields. Both the rate and spatial distribution of ET can be efficiently and accurately quantified independent of the crop development stages or the specific crop type. The analysis estimated evapotranspiration (ET) of irrigated and non-irrigated lands. By comparing ET of these two land uses, an estimate of the amount of consumptive water use for irrigated land can be made. Furthermore the method can detect differences in consumptive use of water by unirrigated crops that use shallow groundwater near streams, unirrigated crops that are a distance above the groundwater system, and irrigated crops. The information can be used by water resource managers to manage water rights in the Klamath basin.