Impacts of Landuse/Landcover change on groundwater recharge potential of the Lusaka Aquifer system using Fuzzy-AHP

Abstract

Landcover transformations exert pressure on aquifer systems by disrupting natural recharge, yet the extent of these impacts remain poorly understood. This study investigated impacts of land use and land cover (LULC) change on groundwater recharge potential zones (GRPZ) on the Lusaka Aquifer System. Geospatial techniques were combined with multi-criteria decision analysis to delineate GRPZs for the years 1990–2022 with seven thematic layers. Results indicated that built-up areas expanded significantly from 70.13 km² to 652.60 km² (830.49 %) while forest and cropland declined by 593.81 ${\text{km}}^2$ (67.10 %) and 258.65 ${\text{km}}^2$ (33.54 %) respectively. The transition matrix showed that built-up areas had a gain of 25.26 % of the total study area, largely sourced from cropland (10.37 %), forest (8.13 %), and vegetation (5.55 %). Forest cover underwent notable transformations with a loss of 25.75 %. Cropland exhibited the highest degree of persistence, with 11.19 % remaining unchanged. The areal coverage of GRPZ showed that low and moderate recharge zones increased by 134.21 km² (27.17 %) and 39.14 km² (3.13 %) respectively. In contrast, high and very high zones declined by 164.90 km² (33.33 %) and 8.47 km² (74.48 %). Analysis of built-up area expansion on GRPZs revealed notable encroachments on low, moderate and high recharge zones by 127.28 km², 332.02 km² and 106.65 km² respectively. This study highlights the ongoing shifts in recharge potential areas driven by urbanization, indicating a continued trend that increases the risk of reduced aquifer recharge and long-term groundwater depletion. The spatial overlap between built-up expansion and recharge potential zones indicates a disconnect between LULC change and groundwater management.