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Groundwater exploitation and recharge rate estimation of a quaternary sand aquifer in Dar-es-Salaam area,Tanzania 总被引：1，自引：1，他引：0
Ibrahimu Chikira Mjemah Marc Van Camp Kristine Martens Kristine Walraevens 《Environmental Earth Sciences》2011,63(3):559-569
Dar-es-Salaam City gets water supply from surface water and groundwater. The groundwater is used to supplement surface water
supply and has increasingly become a major source of water supply in the city. The study area comprises three major parts:
the central coastal plain with quaternary fluvial–deltaic sediments, the deltaic Mio-Pliocene clay-bound sands and gravels
in the northwest and southeast and the Lower Miocene fluviatile sandstones of Pugu Hills in the west of the study area. The
main objective of this study was to quantify the integrated water balance. The major source of renewable groundwater in the
aquifer is rainfall. Hence, the average recharge of 256.2 mm/year (for the year 2006) to the aquifer was estimated using the
balance method of Thornthwaite and Mather, which is equal to 99.4 hm3/year for the whole alluvial aquifer. This value was balanced with total groundwater abstraction of 8.59 hm3/year, baseflow to rivers of 75.7 hm3/year and discharge into the sea (15.11 hm3/year). 相似文献
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Marc Van Camp Ibrahimu Chikira Mjemah Nawal Al Farrah Kristine Walraevens 《Hydrogeology Journal》2013,21(2):341-356
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. 相似文献
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Saltwater intrusion and nitrate pollution in the coastal aquifer of Dar es Salaam, Tanzania 总被引：6，自引：5，他引：1
Yohana Mtoni Ibrahimu Chikira Mjemah Charles Bakundukize Marc Van Camp Kristine Martens Kristine Walraevens 《Environmental Earth Sciences》2013,70(3):1091-1111
Dar es Salaam Quaternary coastal aquifer is a major source of water supply in Dar es Salaam City used for domestic, agricultural, and industrial uses. However, groundwater overdraft and contamination are the major problems affecting the aquifer system. This study aims to define the principal hydrogeochemical processes controlling groundwater quality in the coastal strip of Dar es Salaam and to investigate whether the threats of seawater intrusion and pollution are influencing groundwater quality. Major cations and anions analysed in 134 groundwater samples reveal that groundwater is mainly affected by four factors: dissolution of calcite and dolomite, weathering of silicate minerals, seawater intrusion due to aquifer overexploitation, and nitrate pollution mainly caused by the use of pit latrines and septic tanks. High enrichment of Na+ and Cl? near the coast gives an indication of seawater intrusion into the aquifer as also supported from the Na–Cl signature on the Piper diagram. The boreholes close to the coast have much higher Na/Cl molar ratios than the boreholes located further inland. The dissolution of calcite and dolomite in recharge areas results in Ca–HCO3 and Ca–Mg–HCO3 groundwater types. Further along flow paths, Ca2+ and Na+ ion exchange causes groundwater evolution to Na–HCO3 type. From the PHREEQC simulation model, it appears that groundwater is undersaturated to slightly oversaturated with respect to the calcite and dolomite minerals. The results of this study provide important information required for the protection of the aquifer system. 相似文献
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