THE MEASUREMENT AND USE OF PLAYA/SALINE LAKE EVAPOTRANSPIRATION TO CONSTRAIN BASIN RECHARGE

Ground water discharge, either as direct evaporation or as transpiration (ET) from vegetation utilizing ground water at saline lakes, has long been used under the assumption of steady state, to estimate ground water recharge in ground water systems such as the Great Salt Lake. Recent advances in ground based measurement of evapotranspiration using both micro-meteorological and flux chambers have allowed for both higher precision and higher spatial frequency sampling of fluxes over the complex terrain of a discharge region such as the Great Salt Lake. Additionally, the integration of remotely sensed data into high spatial and temporal resolution ET mapping has grown significantly. However, these advances have not eliminated all issues, particularly when latent heat fluxes are very small and surface heterogeneity is very large, both common features of saline lake environments. In this presentation, evapotranspiration measurements and upscaling using remote sensing data are presented from saline lake systems in both the western US and northern Chile. The use of short field campaigns to estimate seasonal ET is shown to be limited by highly variable surface conditions of some playa/lake systems. Combination models, in which ground based measures of ET are upscaled using remotely sensed data, are shown to have validity only in areas of high latent heat flux, with significantly less accuracy and reliability in areas of low evaporation such as found on salt flat environments.