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.
Highlights
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
The values of objective functions show that the hydrology of the Mutama-Bweengwa, Kasaka and Magoye sub-catchments as predicted by the Water Evaluation And Planning (WEAP) model provides satisfactory confidence for prediction of future streamflow and projection based on future scenarios
Manual calibration and validation were achieved under the historical mode of the model setup where observed discharge from the hydrometric station (Magoye River at Chimbumbumbu) and simulated discharge were statistically evaluated through the Nash-Sutcliffe Efficiency (NSE), and coefficient of determination (R2) according to Equation (2) [25]
Summary
Water is an important resource that drives economies and social well-being of human societies. Several studies have applied the WEAP Model to represent current water conditions at catchment level [10] [11], to explore a wide range of demand and supply options for balancing environment and development [12], to determine relations between reservoir storage, in streamflow, and water supply yield [13], to investigate and assess scenarios of future water resource development under different demands [14] [15] [16] and under irrigation and climate change scenarios [17], and to model the response of small multi-purpose reservoirs to hydrology for improved rural livelihoods [18]. The study recommends sustainable catchment protection and river restoration strategies based on the findings
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