Multi-Temporal GIS-Based Analysis of Surface Water Susceptibility to Pollution in the Kala Oya Basin, Sri Lanka

Abstract

This research focused on identifying pollution-prone areas within the surface water bodies of the Kala Oya basin and developing a Surface Water Susceptibility Index (SWSI) to assess their vulnerability to contamination. The SWSI maps were developed using six main parameters: streams, soil type, ground slope, settlements, land use, and the road network. These factors were analyzed using Arc GIS 10.8 software and the real time data were obtained through sample surveys in 2019. To integrate these multiple parameters, the Multi-Criteria analysis (MCA) was conducted, using the weighted linear combination technique (WLC). This approach enabled a systematic categorization and aggregation of each criteria where its importance is ranked then integrated using expert opinion and review of related studies. The applicability of the SWSI model was further assessed using Inverse Distance Weighted (IDW) interpolated real time water quality data obtained for the Kala Oya basin. The research identified that the pollution risk was moderate in the basin area and it occupied 34.92 % of the total basin area with the lower and the upper basin having a relatively low pollution risk. From the map removal techniques, it was found out that sensitivity of surface water to pollution is more influenced by slope then by soils, road, LULC, and settlement and streams in order. This research calls for specific pollution controls geared towards the sensitive features already distinguished. These findings are evidence that support the measures of pollution control and also is a pointer to how best water quality could be managed for the best results fits most effectively the local water management and land use.