Analysis of Evapotranspiration under Surface Energy Balance Algorithm in Selected Dams: a Case Study in Mai Dimu and Mai Nigus Earthen Dams

Abstract

For sustainable water resource management in semi-arid areas like Tigray, Ethiopia, it is crucial to estimate evapotranspiration (ET). This study evaluates the efficacy of the remote sensing-based Surface Energy Balance System (SEBS) model in estimating daily evapotranspiration (ET) for the central and northwest zones of Tigray, particularly the Mai Dimu (Shire) and Mai Nigus (Axum) earthen dams. We used the Satellite image as a MODIS product to get SEBS input parameters like land surface temperature, albedo, and vegetation indices by getting daily images from the MODIS satellite data, and additionally, the auxiliary data like DEM of the catchment to get actual evapotranspiration. The model outputs were rigorously validated against ground-based Piche Evapometer measurements, utilizing site-specific calibration that resulted in markedly enhanced outcomes at Mai Dimu and Mai Nigus (R² = 0.94, RMSE = 0.75 mm/day, and R² = 0.87, RMSE = 0.28 mm/day, respectively). Hence, the performance of the SEBS model is strongly supported by the statistical metric. The sensitivity analysis showed that SEBS-derived ET was most sensitive to changes in land surface temperature (LST), instantaneous downward solar radiation (DSSR), and surface pressure (SP). This study effectively demonstrated the utilization of the Surface Energy Balance System (SEBS) model to estimate daily evapotranspiration (ET) within the topographically intricate and agriculturally heterogeneous catchments of the Mai Dimu and Mai Nigus Earthen dams.