SPATIAL AND TEMPORAL ANALYSIS OF EVAPOTRANSPIRATION USING SEBAL MODEL IN THE DATA SCARCE MOJO CATCHMENT, ETHIOPIA

Abstract

Evapotranspiration is essential to the hydrological and energy cycles, as well as to the estimation of irrigation needs and water supplies. For improved water resource planning and management, accurate ET estimation is crucial to the measurement of the water balance at the basin, river basin, and regional scales. Remotely sensed data are good alternatives that support the collection of climate data. The objective of this study was to estimate Spatial and temporal analysis of evapotranspiration using surface energy balance algorithm for the land (SEBAL) model in the data scarce Mojo catchment. This study used the SEBAL model to assess satellite evapotranspiration from October to March 2022. For this analysis, net radiation, soil heat flow, sensible heat flux, latent heat flux, surface emissivity, surface temperature, surface radiance, surface reflectance, surface albedo, NDVI, and LAI are calculated. The sensible heat flux is calculated by determining the hot and cold pixels under consideration via the atmospheric stability conditions. Finally, evapotranspiration maps are plotted. Consequently, GRASS GIS software and SEBAL Python were used to determine the daily, monthly, and seasonal evapotranspiration in the research area. The findings demonstrated a good degree of agreement between the evapotranspiration values provided by SEBAL and the FAO Penman-Monteith method, with the latter reporting the lowest error (RMSE = 1.14) and the highest correlation (R2 = 0.96). The estimated ET values for the months of March through October, In March and November, the highest and lowest calculated AET values were 6.43 and 4.2 mm/d, respectively. ET values were computed for emperical methods using REF-ET software. In order to compare the results obtained from the SEBAL approach, the Standard Penman-Monteith value for the weather station was utilized as a reference. The results indicate that, given the SEBAL algorithm's acceptable performance in estimating actual evapotranspiration using Landsat 8 satellite images, it could be a very practical method and play a crucial role in understanding water resource management on various earthly surfaces, which is necessary to achieve sustainable development of water resources in the basin. It is also advised that the SEBAL algorithm be applied in the upper Awash basin's remaining catchment