Modeling approaches and strategies for data-scarce aquifers: example of the Dar es Salaam aquifer in Tanzania |
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| Authors: | Marc Van Camp Ibrahimu Chikira Mjemah Nawal Al Farrah Kristine Walraevens |
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| Institution: | 1. Laboratory for Applied Geology and Hydrogeology, Department of Geology and Soil Science, Ghent University, Krijgslaan 281 (S8), 9000, Ghent, Belgium
2. Department of Physical Sciences, Sokoine University of Agriculture (SUA), P.O. Box 3038, Morogoro, Tanzania
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| Abstract: | Management of groundwater resources can be improved by using groundwater models to perform risk analyses and to improve development strategies, but a lack of extensive basic data often limits the implementation of sophisticated models. Dar es Salaam in Tanzania is an example of a city where increasing groundwater use in a Pleistocene aquifer is causing groundwater-related problems such as saline intrusion along the coastline, lowering of water-table levels, and contamination of pumping wells. The lack of a water-level monitoring network introduces a problem for basic data collection and model calibration and validation. As a replacement, local water-supply wells were used for measuring groundwater depth, and well-top heights were estimated from a regional digital elevation model to recalculate water depths to hydraulic heads. These were used to draw a regional piezometric map. Hydraulic parameters were estimated from short-time pumping tests in the local wells, but variation in hydraulic conductivity was attributed to uncertainty in well characteristics (information often unavailable) and not to aquifer heterogeneity. A MODFLOW model was calibrated with a homogeneous hydraulic conductivity field and a sensitivity analysis between the conductivity and aquifer recharge showed that average annual recharge will likely be in the range 80–100 mm/year. |
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