Tewodros M. Tena^1*, Alick Nguvulu², Dickson Mwelwa³, Phenny Mwaanga²

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¹ Department of Environmental Engineering, Copperbelt University, Kitwe, Zambia.
² Department of Geomatics Engineering, Copperbelt University, Kitwe, Zambia.
³ Business and Information Technology Department, Cavendish University, Lusaka, Zambia.
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Abstract: Located in the semi-arid zone of Zambia, the Mutama-Bweengwa, Kasaka and Magoye sub-catchments have witnessed a high demand for water due to increase in population and socio-economic activities putting more pressure on water resources. This study assesses the hydrological components and ascertains the available water resources and unmet demand in the sub-catchments using the Water Evaluation And Planning (WEAP) Model and hydrometeorological data collected between 1951 and 2018. The model was calibrated and validated on 1971-1981 and 2008-2018 data respectively. The results reveal that the sub-catchments have transitioned from positive to negative water balance with -164.295 Mm³/year for Mutama-Bweengwa, -19.021 Mm³/year for Kasaka and -86.368 Mm³/year for Magoye. Evaporation was 1815.259 Mm³/year for Mutama-Bweengwa, 1162.655 Mm³/year for Kasaka and 1505.664 Mm³/year for Magoye. The demand for water has been increasing over time for various purposes such as irrigation, domestic, urban/rural water supply and livestock. The overall water storage in the sub-catchments showed a negative water balance for the year 2018. The observed and simulated peak streamflow were 8.16 m³/s and 7.7 m³/s occurring during the month of January and February respectively. The WEAP model performance achieved R² of 0.98 during calibration and 0.95 for validation, and an NSE of 0.83 for calibration and 0.85 during validation. The values of objective functions show that the hydrology of the Mutama-Bweengwa, Kasaka and Magoye sub-catchments as predicted by the WEAP model provides satisfactory confidence for prediction of future streamflow and hence projection based on future scenarios.

Keywords: Water Availability, Water Use, WEAP Model, River Catchment, Streamflow, Semi-Arid Catchment Hydrology

Cite this paper: Tena, T. , Nguvulu, A. , Mwelwa, D. and Mwaanga, P. (2021) Assessing Water Availability and Unmet Water Demand Using the WEAP Model in the Semi-Arid Bweengwa, Kasaka and Magoye Sub-Catchments of Southern Zambia. Journal of Environmental Protection, 12, 280-295. doi: 10.4236/jep.2021.124018.

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