Mapping Spatial Distribution of Water Quality Parameters Using GIS in Groundwater of the Kelani River Basin, Sri Lanka

Abstract

The demand for water in Sri Lanka is gradually increasing with accelerated development, mainly for human consumption, agriculture, recreational and industrial requirement. This necessity is exerting considerable weight on the available ground water resources. Kelani river basin is the third largest watershed of the country and considered as the main water source for the greater Colombo which is the main commercial and capital city of the country. The present study focused on application of GIS for graph spatial distribution maps referring for important water quality parameters of the ground water in the Kelani river basin. Total 72 ground water sampling locations were selected for the study and some physic-chemical and microbiological parameters were recorded using standard methods. Most of the wells sampled for the study are being used for drinking purposes. It was found that well water in the later part of the transitional zone of the river basin has acidic nature (4.24-6.14). 90% of sampling locations showed high COD and BOD values were detected in meandering zone compare to transitional and head region of the river basin. 70% of the ground water sampling locations were contaminated with total coliform bacteria where 45% of sampling locations were contaminated with feacal coliform. Conductivity, TDS and hardness values of water were showed increasing trend from the head region through the transition to meandering region. Nitrate, Nitrite and phosphate concentrations were remained acceptable level for Sri Lankan standards for drinking water (SLS). GIS spatial distribution maps give better visual image to understand the spatial distribution pattern to overlook better conclusion. The results of the study showed increasing trend of the pollution load towards the meandering part of the river basin suggesting proper management strategic plan is needed to protect groundwater resources of the Kelani river basin.