Browsing by Author "Kebede, Tesema"

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    Characterizing the Groundwater Potential of Wabi Shebelle River Basin
    (Addis Ababa University, 2015-10) Kebede, Tesema; Mohammed, Mebruk(PhD)
    Water is one of the limiting factors for development in the Wabi Shebelle basin area. The overall quantity of water available in the basin is very insufficient. In addition, the difficult access of water resources in the basin severely restricts their utilization. With an area of some 191146 km2, the WSRB basin mainly comprises the south eastern highlands of the Arsi Bale. The basin is endowed with abundant groundwater resources that require proper management if they are to be wisely utilized in a sustainable manner. With the Wabi Shebelle River as the major resource, the WSRB is the most undeveloped. The groundwater potential in the basin is seldom estimated. The objective of this study is to investigate the regional groundwater characteristics and to assess the groundwater resource potential of Wabi Shebelle river basin. To achieve this objective, a three dimensional groundwater model (TAGSAC) that uses finite element method were applied. Ground water models provide a scientific and predictive tool for determining appropriate solutions to water allocation, surface water – ground water interaction, landscape management or impact of new development scenarios. The model can also be used to simulate possible future changes to hydraulic-head or groundwater-flow rates as a result of future changes in stresses on the aquifer system. The numerical model was calibrated by trial-and-error methods where by hydrogeological parameters like hydraulic conductivity and the recharge amount are adjusted. The relatively small span of physically possible values of head was not considered sufficient to justify the effort required to implement inverse calibration methods. Calibration results provided the estimate on the regional distribution of hydraulic conductivity values, which range from 8.64 x 10-8 m/s to 7.7 x 10-4 m/s over 36 zones resulting in a greater reliability of the spatial and temporal evolution of state variables for simulations. Best model performance achieved, resulted in a mean absolute error of 8.77 m and a root mean square error of 15.30 m (R2 = 0.9992). From this work the estimated replenish able groundwater potential of the study area is about (8700 MCM). Results show that groundwater head have an immediate effect on hydraulic conductivity of the aquifer. And the amount of recharge also has its own effect on the model simulation. Keywords: Numerical Groundwater Flow Models; Finite Element Method, Wabi Shebelle River Basin, Wabi Shebelle River, TAGSAC, Ethiopia