Assessing Long Term LULC Dynamics and Their Influence on Water Availability in the Upper Kafue Basin, Zambia (1994-2024)

Land use and land cover (LULC) change is a major driver of hydrological variability in sub-Saharan Africa’s tropical river basins, yet its long-term impacts on water availability remain poorly understood. This study evaluated the influence of LULC change on water availability in Zambia’s Upper Kafue Basin from 1994 to 2024. Multi-temporal Landsat imagery was classified using Random Forest, Support Vector Machine, Decision Tree, K-Nearest Neighbours, and ensemble machine learning models. Hydro-climatic variables were derived from CHIRPS precipitation, MODIS evapotranspiration (ET), and FAO WaPOR datasets. Spatial LULC–ET relationships were analyzed via Geographically Weighted Regression (GWR), while hydro-climatic impacts were assessed using water balance indicators and the Budyko framework.Forest cover declined from 43.12% to 31.76%, while cropland expanded from 35.67% to 47.38%. Annual ET rose from 903 to 952.4 mm, whereas water availability dropped from 226 to ~55 mm (74.5%). Annual precipitation decreased slightly from 1,129 to 1,010 mm, and the evaporative index increased from 0.80 to 0.94, showing higher atmospheric water return. Budyko analysis yielded a mean aridity index of 1.63 and a catchment parameter ($\omega$) of 3.49, reflecting moderately water-limited conditions. Attribution analysis attributed 70.7% of the decline in water availability to reduced precipitation and 29.3% to increased ET. The GWR model showed low explanatory power (mean local $R^2 = 0.06$), suggesting influence from additional climatic and subsurface processes. Overall, results revealed progressive decoupling between precipitation and water availability, emphasizing the joint impact of climatic aridity and land surface dynamics on hydrological resilience.