Modeling approaches and strategies for data-scarce aquifers: example of the Dar es Salaam aquifer in Tanzania
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Date
2013
Journal Title
Journal ISSN
Volume Title
Publisher
Springer
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 watersupply
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
80–100mm/year.
Description
Journal article
Keywords
Africa, Coastal aquifers, Groundwater flow, Over-abstraction, Numerical modeling