Groundwater Recharge Quantification Using Atmospheric Chloride Mass Balance Approach for Gilgel Abay Catchment, Upper Blue Nile Basin, Ethiopia

Groundwater recharge quantification is a significant topic for water resource management in a given hydrological system. The aim of this study was to quantify the groundwater recharge rate and identify the desirable assumptions for the existing environment. In the catchment area of the study, the point recharge can be estimated using the chloride mass balance method under the condition that runoff is negligible and the impacts of runoff are taken into consideration yields an acceptable result of 287.6 and 217 mm per year, respectively. According to the estimated results, 17.27 percent of the annual rainfall quantity contributes as a recharge under negligible runoff conditions and 13.03 percent under significant runoff conditions. The direct runoff was 483 mm per year and the catchment runoff coefficient of 0.29 a unit less parameter was determined through the hydrograph analysis with the aid of areal precipitation. Aerial depths of precipitation were determined in this study using three methods: arithmetic, thiessen, and isohyetal. The results of their harmonic mean areal depth of precipitation were 1665 millimeters per year, which was used for groundwater recharge calculations. Therefore, the estimation of recharge is vital for the effective utilization of groundwater resources.

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