Browsing by Author "Musnad, Muna Mohmmed"

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    A decision support system for groundwater management of Arusha aquifer, Tanzania.
    (University of Dar es Salaam, 1998) Musnad, Muna Mohmmed
    Water supply robustness and sustainability for Arusha District is the aim of this study. The temporal effect on the aquifer water table corresponding to the current and future demands should be addressed in order to avoid the aquifer depletion. The main objective of this study was to develop a decision support system (DSS) that can address the impacts of demand increase and rainfall shortage on the aquifer. This will ease the decision- maker's task to determine the sustainable extraction volume from this aquifer system. The visual MODFLOW, a three dimensional finite-difference ground water flow model, was used to simulate unsteady flow in Arusha District unconfined aquifer in central northern region in Tanzania. IDRISI a GIS software was used for preparing inputs and analyzing outputs of MODFLOW. A rectangular region (16* 17,6 Km2) was selected for modelling. Several simplifying assumptions were made about boundary conditions and aquifer properties. Some of springs were represented as rectangular drain a few small rivers and evapotraspiration were neglected. The model was calibrated first using a set of observed dynamic water level, aquifer stress parameters and different values of lateral hydraulic conductivity until the best fitting was occurred. The specific storage, total and effective porosity of the aquifer were assumed constant, the atmospheric recharge rate and hydraulic conductance drains were inserted to the model as inputs. Then the values of inputs were used for verification of the model. It was found that the RMSE in calibration (0.805m) and verification processes (0.956) provided acceptable difference between the estimated and observed dynamic water level corresponding to the available record length. The model was then used to predict the dynamic water table levels during 20 years and different scenarios of recharge and pumping rate were applied. It was found that the optimal operating policy, which will satisfy the future demand and guarantee consistent aquifer stress, should comprise of two scenarios no. l and 2 through adjusting the pumping rate by adding the expected increase in the demand to the current pumping rate. Several recommendations were given relating to the way in which this and similar aquifers should be modeled and in management in future.