Groundwater Recharge Estimation Using Distributed Model (Wetspass): The Case of Afa-Selga Watershed, Abay Basin
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Date
2024-07
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Addis Ababa University
Abstract
Understanding the spatial variability of groundwater recharge is crucial for managing and evaluating groundwater resources. In the Afa-Selga watershed Population growth necessitates increased groundwater resources, while water scarcity hinders sustainable development, especially for domestic and agricultural use. Historical rainfall, temperature and wind speed data is crucial for climate studies, water resource processes, and hydrological modeling. Four absolute homogeneity tests were used to investigate the homogeneity of annual rainfall data sets in five meteorological stations in the Afa-Selga watershed, revealing usefulness at a 95% significance level. By preparing inputs in the form of digital maps using remote sensing, GIS tools and processing of meteorological and hydrological observations, that were designed for estimation of the annual and seasonal groundwater recharge, surface runoff, and evapotranspiration amount in the Afa-Selga watershed using WetSpass modeling method, the model spatial and temporal characteristics allow spatially distributed quantification of water balance components. The primary objective of utilizing The WetSpass model was used to estimate annual and seasonal groundwater recharge, evapotranspiration, and surface runoff in the Afa-Selga watershed. Longterm hydro-meteorological and watershed bio-physical data were used for model input. The longterm average annual rainfall of 1246.6 mm was divided into 117.41 mm (9.42%) recharge which is equivalent to 68,039,095 m3 /yr. (579.5 km2), 948.9 mm (80.5%) evapotranspiration, and 125.87 mm (10.08%) surface runoff The hydrological water balance components for the Afa-Selga watershed are accurately simulated by the model. The model performed well, as shown by good statistical values for the correlation coefficient (R2 = 0.89) and Nash-Sutcliffe (NSE =0.84).
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Afa-Selga watershed, Groundwater recharge, water balance, WetSpass model