Application of LANDSAT Data for Field-Scale Comparisons and Basin-Scale Estimates of Evapotranspiration in the Wood River Valley, Upper Klamath Basin, Oregon.

30 meter resolution LANDSAT data were used to evaluate the effects of irrigation management decisions in the Wood River Valley, Upper Klamath Basin, Oregon. The Klamath Basin is well known as an over-allocated system that strains to provide adequate water for agriculture, recreational, and wildlife needs. In an effort to provide increased stream flows after the water shutoff to irrigators in 2001 and disastrous fish kills in 2002, a program was established with cooperative ranchers to withhold irrigation from their cattle pastures in the Wood River Valley, just above Upper Klamath Lake. From 2003 to 2006, ground-based measurements over one irrigated and one unirrigated pasture site were used to monitor the difference in evapotranspiration using the Bowen ratio energy balance method. These data sets represent point measurements of the response to irrigation, but do not allow for the spatial integration of effects of irrigated versus unirrigated lands. The SEBAL and later METRIC algorithms were developed to evaluate evapotranspiration on a field- or basin-wide scale using LANDSAT data. Four LANDSAT scenes of the Wood River basin during the 2004 growing season were evaluated using re-derived and updated METRIC algorithms. The Bowen ratio station micrometeorological data were utilized in the METRIC algorithms. Comparisons of METRIC algorithm output with ground-based data for all components of the energy balance, including net radiation, soil heat flux, sensible heat flux and evapotranspiration, were made for the four scenes. The excellent net radiation estimates, along with less accurate estimates of the other components, is demonstrated. The ability to integrate the effects of withholding irrigation on evapotranspiration and the water balance on irrigated and unirrigated lands within the basin is demonstrated. The results exhibit application of the METRIC algorithms to partition water balance components at the watershed scale.