Water Quality Deterioration in the Malwathu Oya Basin, Sri Lanka and the Need for Physics-based Modelling

Water quality in the Malwathu Oya basin, Sri Lanka, has been deteriorating due to pollution created by the anthropogenic activities such as agriculture, domestic and industrial waste disposal, urban and rural infrastructure development and deforestation. Further, the behaviour of excess nutrients applied to crops in the upstream as fertilizers and transferred to the waterways, remain unresolved. The lack of proper monitoring and scarcity of progressive water quality data is severely affecting the studies of systematic and quantitative assessment of water quality degradation issues as well as identification of preceding causes. This paper reviews several studies conducted on the water quality of the basin and recommends to establish a physics-based model which could incorporate detailed analyses of water resources management alternatives and the behaviour of the nutrients, as a remedial measure to address the data scarcity for basin-wide water quality management in major river basins in Sri Lanka.