Evaluation of Recharge and Shallow Groundwater Dynamics in the Upper Awash Basin, Central Ethiopia

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Addis Ababa Universty


The increasing demand placed on groundwater has encouraged distinguishing of this resource, which would be the foundation of exploration, management, and conservation. In this study, quantitative analysis of groundwater resources of upper awash basin and shallow groundwater dynamics has been made. Therefore, the main objective of the present research study was evaluation of groundwater recharge using river discharge records and water balance techniques. Hence, for recharge evaluation using baseflow the most important rivers selected from the upper awash basin were Awash River at Bello, Awash River at Hombole, Mojo, Akaki, Berga, Holleta and Teji River catchments have been identified as the crucial area for assessing the recharge procedure. As a result, the annual recharge of the basin using baseflow separation is 130.5mm, which is 12.8% of annual rainfall recharged the aquifer. Baseflow index (contribution of groundwater to rivers) is highest during the dry season and lowest at the time of rainy season in contrast greater precipitation and smaller evapotranspiration rates during the summer months create greater baseflow in the basin. Consequently, baseflow of Akaki catchment which is upper basaltic aquifer and the Holleta catchment which is lower basaltic aquifer have high baseflow of 23% and 31% whereas, Teji River, Awash Hombole, Awash Melkakunture, Awash Bello and Hombole have 14%, 13%, 1% and18% correspondingly. Additionally, using the water balance technique, the annual recharge of the basin found to be 238.02mm, which is 23.4% of annual rainfall is percolated to the aquifer. However, groundwater recharge evaluated by water balance in the upper awash basin takes place in three months June to August. From the shallow aquifer system, in the upper awash basin, several parameters observed from groundwater table contour map like local groundwater flows, divergent and convergent zone, local groundwater divide. According to the shallow groundwater table contour map areas which groundwater converge are discharge zones and are located in north-eastern part, in Becho plain, Akaki well field and southern part of Adaa plain areas i.e. at this convergent zone, water comes from almost all direction of the study area; and areas which are divergent zones are located in the north-west and south-east part of the study area. Key words: Baseflow Separation, Ethiopia, Groundwater Well Inventory, Shallow Groundwater Dynamics, Upper Awash Basin, Water Balance



Baseflow Separation, Ethiopia, Groundwater Well Inventory, Shallow Groundwater Dynamics, Upper Awash Basin, Water Balance