VALIDATION OF A HYBRID EVAPOTRANSPIRATION MODEL USING SATELLITE IMAGERY AND PRECIPITATION-FLOW DATA

Abstract

To quantify the water balance in watersheds, it is necessary to know the components of the hydrologic cycle, especially evapotranspiration (ET). Many studies have been conducted using a single-source model such as SEBAL to estimate the actual ET (ETa) from satellite imagery; however, other models have been developed and continuously improved, such as the Two Source Energy Balance (TSEB). This study evaluated ETa estimation performed by a hybrid TSEB ET model programmed in the Spatial Evapotranspiration Modeling Interface (SETMI) using satellite imagery. The evaluation was conducted over two full hydrological years, developing a new methodology to convert hourly ETa data to monthly and annual data. The results of applying the TSEB/SETMI model to Landsat 8 imagery were validated to a water balance calculation from field measurements in three representative watersheds in Corumbataí, SP, Brazil. Thus, it was concluded that the adjustment applied to monthly and annual ET data produced results statistically correlated to those obtained through a simplified annual water balance, confirming that the developed methodology can be used to estimate monthly and annual ET from Landsat 8 imagery and the hybrid ET model.