Climate Change Impact Assessment on Water Resources: A Case Study of the Mulungushi River, Zambia

Abstract

Climate change is increasingly altering hydrological processes, posing serious threats to water resource sustainability, ecosystem health, and socio-economic development. This study assessed the impacts of climate change on the water resources of the Mulungushi River catchment in Central Province, Zambia, with the objective of evaluating long-term hydro-meteorological trends and predicting future river hydraulic conditions. Historical rainfall, temperature, evaporation, discharge, and water-level data covering the period 1993–2023 were analyzed using statistical trend analysis in Microsoft Excel and spatial analysis in QGIS. A hydraulic model of the Mulungushi River was developed in HEC-RAS using cross-sectional geometry, discharge records, and boundary conditions to simulate river flow characteristics under steady-flow conditions. The results revealed a persistent decline in regional rainfall, with an average trend of −3.0348 mm/year, indicating increasing climatic variability across the catchment. Analysis of observed stage records showed fluctuations in river water levels, while HEC-RAS simulations projected a reduction in average water levels from approximately 2.204 m to 1.602 m over the projected period. Hydraulic simulation further indicated subcritical flow conditions throughout the river reach, with maximum channel velocities below 1.27 m/s and Froude numbers less than one. The findings demonstrate that continued climatic variability is likely to reduce water availability and alter river hydraulics, with implications for irrigation, domestic water supply, and hydropower generation. The study provides a scientific basis for sustainable water resources management and climate adaptation planning within the Mulungushi River catchment and similar river basins in Zambia.