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

¹ Laboratory of Geoengineering and Environment, Research Group “Water Sciences and Environment Engineering”, Department of Geology, Faculty of Sciences, Moulay Ismail University, Zitoune, BP11201 Meknes, Morocco.
² Division of Soil and Water Management, Department of Earth and Environmental Sciences, Faculty of BioScience Engineering, Katholieke Universiteit Leuven, 3000 Leuven, Belgium.
³ Geo-Resource, Geo-Environment and Oasis Geological Heritage Research Group, Engineering Sciences and Techniques Laboratory, Geosciences Department, Faculty of Sciences and Techniques, Moulay Ismail University Presidency, Marjane 2, Meknes BP 298, Morocco.
⁴ National Institute for Scientific and Technological Research in Water, University Ibn Zohr - Agadir ·
⁵ Geography and Tourism Research Group, Department Earth and Environmental Science, KU Leuven, Celestijnenlaan 200E, 3001 Heverlee, Belgium.

^* Corresponding author: a.oumou@edu.umi.ac.ma; abdellah.oumou@kuleuven.be

Abstract

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.