MONITORING DAILY ACTUAL EVAPOTRANSPIRATION AND SURFACE WATER STATUS OVER AN AGRICULTURAL AREA IN WESTERN ALGERIA USING REMOTE SENSING DATA

Abstract

The quantification of evapotranspiration from agricultural areas is important for agriculture water management, especially in arid and semiarid regions where water deficiency is becoming a major constraint in economic welfare and sustainable development. Remote sensing based energy balance models are presently most suited for estimating evapotranspiration at both field and regional scales.

In this study, METRIC (Mapping Evapotranspiration at high Resolution with Internalized Calibration), a remote sensing of spatializing, has been applied for the estimation of actual evapotranspiration in the Ghriss plain, a semiarid region in Algeria with heterogeneous surface conditions. Eight images acquired by the Lansat-7 satellite on 2002 were used. The METRIC model followed an energy balance approach, where evapotranspiration is estimated as the residual when the net radiation, sensible heat flux and soil heat flux are known. Different moisture indicators derived from the evapotranspiration were then calculated: evaporative fraction, Priestley-Taylor parameter and surface resistance to evaporation. These calculated indicators facilitate the quantitative diagnosis of moisture stress status in pixel basis. The obtained results concern the validation of the used model for spatial distribution analysis of evapotranspiration and moisture indicators. The evaluation of evapotranspiration and surface energy fluxes are accurate enough for the spatial variations of evapotranspiration rather satisfactory than sophisticated models without having to introduce an important number of parameters in input with difficult accessibility in routine. In conclusion, the results suggest that METRIC can be considered as an operational approach to predict actual evapotranspiration from agricultural areas having limited amount of ground information.