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.