Groundwater movement beneath watershed divide is one component of the hydrological\ncycle that is typically ignored due to difficulty in analysis. Numerical groundwater\nmodels, like TAGSAC, have been used extensively for predicting aquifer responses\nto external stresses. In this paper TAGSAC code was developed to identify the\ninter-basin groundwater transfer (IBGWT) between upper Awash River basin (UARB)\nand upper rift valley lakes basin (URVLB) of Ethiopia. For the identification three\nsteady state groundwater models (for UARB, URVLB and for the two combined basins)\nwere first created and calibrated for the 926 inventoried wells. The first two\nmodels are conceptualized by considering the watershed divide between the two basins\nas no-flow. The third model avoids the surface water divide which justifies\nIBGWT. The calibration of these three models was made by changing the recharge\nand hydrogeologic parameters of the basins. The goodness of fit indicators (GoFIs)\nobtained was better for the combined model than the model that describes the\nURVLB. Furthermore, the hydraulic head distribution obtained from the combined\nmodel clearly indicates that there is a groundwater flow that doesn�t respect the surface\nwater divide. The most obvious effect of IBGWT observed in these two basins is\nthat it diminishes surface water discharge from URVLB, and enhances discharge in\nthe UARB. Moreover, the result of this study indicates potential for internal and\ncross contamination of the two adjacent groundwater.
Loading....