Catchment Protection of Gin Ganga (River) as part of Water Safety Plan (WSP) in Greater Galle Water Supply Scheme (GGWSS)

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.