Groundwater Recharge Estimation Using Wetspass Model in Upper Bilate Catchment: South Weastern Escarpment of Main Ethiopian Rift
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Date
2015-06-06
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Addis Ababa University
Abstract
The study area, upper Bilate Catchment, is strongly dependent on groundwater like other rural catchments in the country. The main objective of this thesis is to quantify the amount of groundwater recharge in upper Bilate catchment. Recharge was estimated using physically based distributed recharge model called Wetspass. As input to the model precipitation, potential evapotranspiration, temperature and wind speed were estimated using data collected from meteorological stations located within and nearby the basin, The physical environmental data including land use, soil type, and groundwater depth are evaluated from field observation and existing maps. Slope and topography were generated from SRTM data. .
The mean annual recharge of the catchment using the model was found to be 9.4 % of the precipitation, whereas the direct runoff was found to be 20 % of the precipitation. The study area is characterized by lower groundwater recharge relative to surface runoff due to the effect of impermeable soils, morphology of land and land use/land cover of the study area. The western and northern parts of the area are identified as recharging zone and the central and southern part is discharge zone. The resulted groundwater recharge zoning map was validated using base flow separation method and also compared with previous groundwater recharge works of the study area. Finally, it is concluded that the groundwater recharge estimation using Wetspass model is reasonable and useful for quantification of annual groundwater recharge with special and seasonal variation and also capable in the identification of groundwater recharge Zones.
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Upper Bilate River, Groundwater Recharge, Wetspass Model Runoff and Evapotranspiration