Spatial & temporal impacts of climate and LULC on water quality in the Kelani river basin

Abstract

The Kelani River, a major freshwater resource in Sri Lanka, has experienced significant water quality degradation over the past two decades due to land use and land cover (LULC) changes and climate variability. This study investigates the spatial and temporal impacts of these factors on key water quality parameters from 2003 to 2023 across the upstream, midstream, and downstream segments of the river. Using remote sensing, GIS (ArcGIS Pro), and statistical analysis in Python, the study evaluates relationships between LULC categories and water quality parameters, as well as between climate factors and water quality parameters such as pH, dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), nitrate, phosphate, turbidity, electrical conductivity (EC), and temperature. Findings reveal a substantial increase in developed land, particularly downstream, alongside a decline in vegetation, which contributes to elevated organic pollution and reduced oxygen levels. Strong positive correlations (r=0.86) were observed between rainfall and turbidity, as well as temperature and BOD (r=0.61), highlighting the influence of seasonal climate variability on water quality of midstream and downstream. These results underscore the need for integrated watershed management that accounts for both spatial and temporal variations in land use and climate, to safeguard the Kelani River’s water quality and support sustainable resource planning.