Application of Water Quality Simulation for Water Safety Plan at Mahaweli River Basin, Kandy

Abstract

Water Safety Plan (WSP) is an effective risk assessment framework to elaborate possible risks for water supply systems. However, risk quantification of “severity” and “likelihood” of specific incidents is challenging especially for the risks at water sources. Water quality simulation is an essential tool for predicting the risks and applying effective countermeasures, while data availability and usability for practitioners remains as obstacles for implementation. The objective of this study is to develop appropriate simulation methodology for the risks at water source of all the water supply systems in Sri Lanka. In this report, we focused on the Mahaweli river basin in Kandy. Reviewing the existing WSP at Greater Kandy WTP, the contamination of intake water by the leachate from neighbouring solid waste damping site was considered as a significant risk. We developed dynamic hydraulic model and water quality model which can configure input and output data on Microsoft Excel interface. As a result of the simulation, it was implied that the contaminant from the leachate can flow back to the intake of the WTP due to density flow. Re-risk assessment for possible countermeasures showed the structure modification and leachate treatment are effective to mitigate the risk for water quality hazards.