Evaluation of water quality in the upper and lower catchments of the Kelani River Basin, Sri Lanka

Kelani River is the principal consumable water source for 80% of the population in the Colombo district and an important eco-system complex for the freshwater fish biota of Sri Lanka. However, it is the most polluted river in the country. The present study was conducted to determine the water quality parameters and pollution of the upper and lower catchments of the river and select the most suitable parameters for predicting the pollution of each catchment. Thirteen locations of each catch-ment were selected for the study, and 14 water quality parameters were recorded by standard techniques. Measurements were compared with the standard values permissible for drinking purposes and aquatic life and subjected to principal com-ponent analysis. The study revealed that the most polluted catchment of the Kelani River was the lower catchment, and the chemical oxygen demand (COD) and water pH were selected as the most suitable parameters to predict the pollution levels of the lower catchment. The nitrate concentration and COD were selected as the most suitable water quality parameters to predict the pollution of the upper catchment. The present study indicates an accelerating trend in water pollution of the Kelani River when compared with studies conducted two decades ago.