NVESTIGATION OF OPTIMUM POLLUTION MANAGEMENT STRATEGY IN WANKA RIVER BASED ON WATER QUALITY MODELING

Abstract

i Abstract Despite the high socio-economic importance of Wanka River for the local communities, the increased anthropogenic (domestic and agricultural) pollution released in to the River has created a non-conducive environment for the aquatic life and ecology. This has necessitated efficient water resources management of the watershed. This study was conducted with a prime aim of conducting water quality modeling using QUAL2Kw in the Wanka River to investigation the optimum pollution management strategy based on the evaluation of three hypothetical scenarios which is necessary for decision makers to safeguard Wanka River and its end users. The study was conducted on 9.24 km River reach which divided into 10 segments. Four monitoring stations were selected based on basic criteria. Water quality data were collected for two months (February and April). Calibration is done for April where the model fitness value is 0.90 and validation is done for February which have a model fitness value of 0.91. It is observed from the model result that except for some parameters there is quite good agreement against the field data. The existing condition of the river is taken as the base scenario and it is compared with first, second and third scenarios where pollution modification was done and Biochemical oxygen demand (BOD) is reduced by 3.44%, 0.39%, and 99.69% respectively. The dissolved oxygen (DO) is also increased by 9.66% for the third scenario. The third scenario is selected since it is effective in raising DO levels and the model shows a good response when compared with other scenarios maintaining the targeted water quality criteria (minimum DO at or above 4mg/L and Chlorophyll-a of 0.02mg/L). The model result shows that Wanka River water quality is good on the upstream of the town and degraded as it flows downstream. It can be concluded that pollution management and control strategy could be a possible approach for better river water quality management, pollution reduction, aquatic life protection and secure sustainable development in Wanka River as this study identified reach 7, 6.62 km downstream of the head water station to address River water quality issues effectively which has never been done previously.