Overexploitation of water supplies remains the most serious constraint on its sustainability, and many authorities are confronting serious problems in its management because of growing competition for the ever-dwindling natural resource. The study aims to assess the supply and demand for water in the Walatsi sub-catchment from 2022 to 2030. Data from key informants, experiment, direct observations, and GIS analyses were utilized and analyzed through QGIS software and Microsoft Excel, and a decision support system - WEAP model was adopted for scenario analysis and simulations. Using WEAP’s built-in supply and demand database, available water supply, present and future water demand, and water balance were determined, and a correlation between simulated water balance and demand was established to interpret water balance results further. Results from the study indicated an annual supply between 31.63 and 31.65 Million cubic meters (Mm3) and a monthly supply ranging from 0.48 to 6.80 Mm3. An annual increase in water demand by 27.59% from 6.45 Mm3 in 2022 was observed, which further revealed a declining annual water balance by ？7.07% from 25.18 Mm3 in 2022 and an increasing annual monthly water deficit in February from ？0.02 to ？0.15 Mm3. The ？0.999 coefficient explained the unmet demand gap from 0.24% to 1.85%. Variations in monthly supply annually are due to the bimodal dry and rainy seasons, and annual supply is due to regular and leap years. The positive trend in demand is likely to put pressure on available water supplies. An increasing deficit indicates pressure on water sources and exploitation of the reserve. This study, therefore, indicates a water scarcity sub-catchment.
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