Abstract:
Gin Ganga (River) is the main raw water source to Greater Galle water Supply Scheme (GGWSS). Managing
drinking water quality from catchment to consumer is the main objective of the Water Safety Plan (WSP) of GGWSS.
There are three Water Treatment Plants (WTP) purifying and delivering 80,000m³ of treated water per day to
approximately 450,000 people through 15 distributions centers. The Gin River has a total length of 113km and a
catchment area of about 932 km² Catchment of the Gin River includes Galle, Matara, Ratnapura and Kalutara
administrative districts. The Gin River originates from the Gongala mountains in Deniyaya and flows to the Indian
Ocean at Gintota in Galle. Gin River annually discharges about 1268 million m³ of water to the sea. Rainfall pattern in
the catchment is bimodal, falling between May and September and again between November and February. Rapid
changing of land use pattern and high rate of application of agrochemicals and fertilizers has significantly affected the
raw water quality. A quantitative and continuous assessment of water quality along Gin River is necessary to identify the
trends and to develop sustainable remedial actions. Content of heavy metals in raw water is also an important parameter
to be tested due to lack of previous data. The WSP Team is already established and the Greater Galle WSS WSP has
been completed. The External Stakeholder Team consists of relevant stakeholders; the Galle District Secretary, relevant
Divisional Secretaries, Health Authorities, Irrigation Officials, Agriculture Officials, Central Environmental Authority
etc. The initiatives and the encouragement of the External Stakeholder Team to implement the catchment protection
program for Gin River is commendable as the group has already carried out a Sanitary Survey and pollution source
identification exercise along the Gin River. The objective of this paper is to present the Water Quality Modeling System
prepared for Gin River and its effectiveness in protecting the catchment to effectively implement the Greater Galle WSS
Water Safety Plan.
