Evapotranspiration measurements of native vegetation, Owens Valley, California, June 1986. Water resources investigation

Evaportranspiration (ET) is a major component of a hydrologic budget, but one of the least understood. Measurements of ET at the land surface are usually point measurements because of local effects caused by the immediate surroundings. These point measurements can be made by using the Bowen-ratio or eddy-correlation methods. It is useful to know how far these measurements can be extrapolated over a large area, such as a basin. Remote sensing of reflected and emitted radiation offer methods to estimate ET spatially and temporally. Measurements were made at three study sites in Owens Valley, California, in June 1986, to compare the results of ground-based Bowen-ratio and eddy-correlation systems with airborne radiometric methods and satellite Thematic-Mapper data. The results of the comparison indicate that all the methods used gave approximate values of ET at each of the study sites. The daily ET derived from all methods was similar, indicating that each adequately described water loss from each of the sites.