Utilizing Remote Sensing to Quantify Evapotranspiration: A Case Study of the Saiss Basin (Morocco)

In areas highly affected by drought in a changing climate, evapotranspiration (ET) becomes a significant parameter affecting soils and vegetation. ET estimation on a large scale remains a problem in understanding the hydrologic system; it is complicated over heterogeneous land use and land cover. However, the availability of remote sensing imagery and local weather data has made ET mapping possible through the application of models. In this study, the METRIC model was applied using Landsat satellite imagery and climatic data. This involves resolving the surface energy balance equation by calculating net radiation, soil heat flux, and sensible heat flux. Two satellite images were used at a resolution of 15m: one for January as a wet season and another for July as a dry period. ET ranges between 2 and 12 mm/day. Higher values are estimated during the dry period, and lower values are attributed to the wet period. Furthermore, water bodies and vegetation are characterized by significant ET compared to bare soils and urbanized areas. The comparison of METRIC ET and reference ET showed a strong correlation with an R², RMSE, and MAE of 0.68, 1.0, and 0.78, respectively. This study can assist managers in their water and agricultural adaptation strategies against climate change.