Groundwater Vulnerability and Pollution Risk Assessment in the Case of Upper Awash River Basin

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Addis Ababa University


Water used for different purposes is harvested in the watershed system; largely in the river basin system. To maintain the requirement of these purposes, both quantity and quality of water for ecological, social and economical development could be manage appropriately through integrated water resource management. However, scarcity and poor water quality are the major challenges of the world due to climate change and water pollutions. These challenges trigger further ecological, economical and public health impacts. In Ethiopia, evidence shows that upper Awash River sub-basin is the most impacted river basin that is why protection of both groundwater and surface water resources come to an essential approach through investigation of hazards, vulnerability and consequences of the water sources. This research is designed to identify vulnerable and risk of ground water pollutions so as to indicate the requirements of protection of vulnerable aquifer considering seven important factors of groundwater vulnerability as well as land use management. To achieve these objectives, digitized data for parameters and secondary data from concerned sectors have been collected. These collected data and Shape files have been analyzed using ArcGIS 10.2 software and SPSS version 24. Sensitive analysis, model validation, vulnerability index and risk index have been produced. Accordingly, as the difference in percentage (6.48% - 16.77%) of theoretical weights and effective weights is not much more differ, theoretical weights are used for DRASTIC model analysis and also variation index due to removal of each parameter, the most sensitive parameters to groundwater pollution orderly are Impact of Vadose Zone, Depth of water, Aquifer media, Soil type, Topography, Net Recharge and Hydraulic conductivity. The validation confirmed that 72% of variation in index values is related with nitrate concentration and a unit increase of nitrate concentration increase vulnerability index by 2.26 times. Step by step analysis of each intrinsic parameter has been done. Upper Awash sub basin has 18% high and very high vulnerable area; 26% moderately vulnerable area and 57 % very low and low vulnerable areas whereas only 1% of the area is high risk of pollution; 31% of the area is moderate risk pollution; and 67% of the area is low risk for groundwater pollution. The output of this study will have greatest advantage for groundwater protection measures provide that the limitation of environmental variability and qualitative index methods. Researchers are recommended to support these findings with field observations and strong approaches for further potential risks of groundwater in those identified vulnerable areas.



Pollution, Upper Awash River Basin, Groundwater