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Accueil du site → Master → Pays Bas → 2009 → Assessment of groundwater development potential in the Daka catchment in the Northern Region, Ghana

UNESCO-IHE Institute for Water Education, Delft (2009)

Assessment of groundwater development potential in the Daka catchment in the Northern Region, Ghana

Bruce, C.

Titre : Assessment of groundwater development potential in the Daka catchment in the Northern Region, Ghana

Auteur : Bruce, C.

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2009

The upsurge of guinea worm disease due to the lack of safe drinking water supply hasnecessitated this research to evaluate groundwater potential and quality for designing suitablegroundwater development scenarios for Daka catchment, which is about 7,820 km2 in theNorthern Region of Ghana.Analysis of collected borehole data indicates that the aquifer system can be characterised by ashallow regolith aquifer underlain by a fractured aquifer. Current groundwater abstractionstake place in the regolith aquifer. Groundwater recharge was estimated from hydrographseparation of daily river discharge. The estimated annual average groundwater recharge was44mm, accounting only for 3.9% of average annual rainfall. Groundwater discharge assumesin the form of springs and seepage to local streams. Analysis of water samples indicated thatgroundwater quality is generally good for water supply.A steady-state groundwater flow model was constructed for the Daka catchment. The modelconsists of two model layers representing two aquifers. The model boundaries coincide withthe catchment boundaries (water divides) represented by no-flow boundaries. The model gridis 1000x1000 m2, evenly spaced across the model area. Hydrological stresses include rechargefrom precipitation, abstraction and drainage to rivers. Hydraulic conductivities were estimatedfrom distribution of rock formations and limited pumping test data. The model waspreliminarily calibrated against measured groundwater levels and river base flow, by alteringassigned hydraulic conductivity, drain hydraulic conductance and recharge. The simulatedgroundwater distribution mimics the topography in the catchment.The model was used to assess groundwater development potentials. Two scenarios wereanalysed. One scenario is to provide safe drinking water supply based on current waterdemand. Another is to supply drinking water for the projected water demand in 2020. Sincethe specific capacity of the aquifers is low, pumping wells with low pumping capacity andlong distance between the wells were designed. The model was used to simulate the effects ofabstraction on groundwater levels and river base flow. The results show that the abstractionrate is very small compared to groundwater recharge ; the drawdown caused by increasingabstraction is limited ; the effect on river base flow is also small. Although the regolith aquiferis not very productive, it can provide sufficient safe drinking water supply for ruralcommunities

Sujets  : groundwater analysis aquifers hydrography Ghana


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