Spatial Analysis of Base Flow and Stream Flow from the Abbay River Basin after Watershed Management Interventions

Recently, increasing concern in Africa has been registered on the potential impacts on base flow and stream flow due to the implementation of watershed management interventions. This research incorporates spatially monthly geographical hydrological data sets into a developed spreadsheet water balance model to estimate the changes in surface runoff, base flow and stream flow as a result of implementing watershed management interventions in the Abbay River Basin during the period (2010-2018). The model was implemented at sub-catchment level. Considering Year 2005 as a datum for watershed management intervention, results of the modeling and spatial analysis indicated that watershed management interventions relatively reduced surface runoff, increased deep infiltration to groundwater and accordingly increased base flow to the stream. Among the key results in the Abbay Basin that change from Year 2010 to Year 2018 was reduction of surface runoff from the Abbay Basin in the amount of 1,753 million m3/yr. As a result, an increase in annual base flow in the amount of 23 million m3/yr was estimated, leaving a reduction in annual mean flow of the Abbay River in the amount of 1,731 million m3/yr of the Abbay River at El-Diem site. It is expected that the flow of the Abbay River will continue to decrease due to the continuous implementation of the watershed management interventions and agriculture expansion in the Abbay Basin.