Simulation of Coastal Salinity Susceptibility in Bentota,Sri Lanka

Seawater intrusion is increasing in Bentota area, Sri Lanka while diminishing the land productivity and yielding poor food production and making several socio economic issues for the community in the area. Key innovation of this study is to model coastal salinity susceptibility in Bentota area based on the future scenario of climate change to mitigate land degradation. The temporal and spatial distributions of five parameters of soil (moisture, EC, pH, chloride, nitrate) and eleven parameters of ground water and surface water (pH, EC, TDS, DO, chloride, nitrate, sulfate, calcium, magnesium, sodium and SAR) were monitored considering the sample data collected from July 2016 to June 2017 and analyzed applying Arc GIS software. Water quality was assessed in terms of index based on the standards of World Health Organization. Soil parameters were reclassified in to respective salinity classes based on acceptable standards.

Spatial distribution of soil salinity, ground and surface water quality were integrated using multi-criteria evaluation approach to determine level of coastal salinity. Results of this analysis vigorously indicate that highly salinized, moderately salinized and slightly salinized land extent with respect to the total land extent were 3.4%, 39.6% and 57% respectively; whereas entire area is facing the threats of seawater intrusion and coastal salinity effects by year 2025. This salinity susceptibility model will facilitate for the spatial planning of future land use of this area by providing guidance to local authority in the process of allocating salinized lands for development activities.