Water Quality Modelling of Gin River Downstream

Abstract

This study was aimed to evaluate the water quality of Gin River downstream by using QUAL2k modelling software. Calibrated and validated QUAL2k model was used to predict key water quality parameters; Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Nitrate (TN) and Total phosphate (TP), between Lankagam and Wackwella (83 Km) along the downstream of Gin River. Predicted water quality along the river downstream were compared with the available WQ standard (centra! environment authority, WHO). Calibrated model showed that Lankagama to Batuwangala had a good WQ for drinking with a simple treatment while that for Batuwangala to Keppetiyagoda had average WQ and Keppetiyagoda to Wakwella had minimum WQ. It was also noticed that for washing and bathing, Lankagama to Thawalama except Neluwa has a good WQ while Thawalama to Wakwella had average WQ. As a further improvement of the research, user-friendly software was developed separately which can visualize the model results clearly in any location between the upstream (Lankagama) and downstream (Wakwella). In spite of some limitations, it is recommended to use calibrated QUAL2k model for water future resources management in Gin River downstream.