Groundwater Modelling of Motloutse Alluvial Aquifer, Eastern Botswana
- 1 Botswana Geoscience, Lobatse, Botswana
- 2 Geology Department, University of Botswana, Gaborone, Botswana
- 3 Geology Department, University of Botswana, Gaborone, Botswana
- 4 Geology Department, University of Botswana, Gaborone, Botswana
- 5 Geology Department, University of Botswana, Gaborone, Botswana
- 6 Department of Environmental Sciences, Centre of Excellence: Adaptation and Resilience, University of South Africa, Johannesburg, South Africa
Abstract
The potential groundwater reserve in alluvial aquifers and sandy river beds has not been well studied, and yet their benefit in meeting rural water supply demands cannot be underestimated. A three-dimensional steady-state finite difference numerical groundwater flow model was used to assess the groundwater resource potential on a one-kilometre river stretch scale along the Motloutse River catchment in eastern Botswana. The model area is a single-layer unconfined aquifer system. A uniform grid was laid over this phreatic aquifer, and an overall size of 50 columns x 54 rows was developed. The model yielded calibrated K values of 145 m/day and 11 m/day for the riverbed and riverbank sediments, respectively, and calibrated recharge and evaporation of 172 mm/yr and 120 mm/yr, respectively. A sustainable groundwater yield of 120 m 3 /day with the potential to irrigate an area of 2.4 hectares was determined. The result also shows that the Motloutse alluvial aquifer yields a safe yield of 29,400 m 3 for a kilometre of river stretch.
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