Assessing land-use/land-cover influence on surface water quality using a weighted inverse distance function in Bangweulu sub-catchment area, Zambia

Water quality is crucial for human health and aquatic ecosystems, and understanding the relationship between land use/land cover (LULC) and water quality is essential as urban and industrial growth expands. This study aimed to investigate the influence of LULC on specific water quality parameters, establish the Water Quality Index (WQI) for 34 sampling points, and assess the impact of LULC on the WQI. The study used parametric weighted distance function where the weighted inverse distance function (WIDF) was used in determining the contamination effective contribution area (Aec) for each LULC type of a particular location using Landsat 2020 classified image and 30 m DEM. The results showed a wide range of WQI values, with several significant correlations between LULC and water quality. Turbidity, total dissolved solids (TDS), iron (Fe²+), and electrical conductivity (EC) showed strong correlations with LULC (R² > 0.7). Turbidity and Fe²⁺ were more correlated with built-up and forested areas (p-Value <0.05), respectively. Whereas, TDS and EC were more correlated with cropland (p-Value <0.05). The feacal coliform showed a weak correlation with LULC (R² = 0.258), but had a significant correlation with built-up areas (p-Value <0.05). The WQI had a reasonable correlation with LULC (R² = 0.649). Understanding these relationships could improve decision-making on land use planning and water quality management, predict river water quality, and shape sustainable LULC policies. This information could also help identify hotspots of potential water quality degradation and pinpoint areas for targeted interventions and restoration efforts.