Potential water supply of a small reservoir and alluvial aquifer system in southern Zimbabwe


Hamer, W. de and Love, D. and Owen, R. and Booij, M.J. and Hoekstra, A.Y. (2007) Potential water supply of a small reservoir and alluvial aquifer system in southern Zimbabwe. In: 8th WATERNET/WARFSA/GWP-SA Symposium, 31 October-2 November 2007, Lusaka, Zambia, 31 October-2 November 2007, Lusaka, Zambia.

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Abstract:Groundwater use by accessing alluvial aquifers of non‐perennial rivers can be an important additional
water resource in the semi‐arid region of southern Zimbabwe. The research objective of the study was to
calculate the potential water supply for the upper‐Mnyabezi catchment under current conditions and
after implementation of two storage capacity measures. These measures are heightening the spillway of
the ‘Mnyabezi 27’ dam and constructing a sand storage dam in the alluvial aquifer of the Mnyabezi River.
The upper‐Mnyabezi catchment covers approximately 22 km2 and is a tributary of the Thuli River in
southern Zimbabwe. Three coupled models are used to simulate the hydrological processes in the
Mnyabezi catchment. The first is a rainfall‐runoff model, based on the SCS‐method. The second is a
spreadsheet‐based model of the water balance of the reservoir. The third is the finite difference
groundwater model MODFLOW used to simulate the water balance of the alluvial aquifer. The potential
water supply in the Mnyabezi catchment under current conditions ranges from 2,107 m3 (5.7 months) in
a dry year to 3,162 m3 (8.7 months) in a wet year. The maximum period of water supply after
implementation of the storage capacity measures in a dry year is 2,776 m3 (8.4 months) and in a wet
year the amount is 3,617 m3 (10.8 months). The sand storage dam can only be used as an additional
water resource, because the storage capacity of the alluvial aquifer is small. However, when an
ephemeral river is underlain by a larger alluvial aquifer, a sand storage dam is a promising way of water
supply for smallholder farmers in southern Zimbabwe
Item Type:Conference or Workshop Item
Engineering Technology (CTW)
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Link to this item:http://purl.utwente.nl/publications/61710
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