Projecting turbidity levels in future river flow: a mathematical modeling approach

Climate and land use change impacts on river flow were evaluated in this study with emphasis placed on turbidity. Turbidity levels for the year 2020 were projected for Gin River, one of the prime sources of drinking water in Southern Sri Lanka. Future land use in the Gin catchment was predicted using a GIS based statistical regression approach. Regional Climate Modelling system generated the future rainfall for the SRES A2 and SRES A1B emission scenarios. Streamflow simulations were carried out using a distributed hydrologic model, and turbidity values were determined using rating curve based relationship developed between river discharge and TSS (Total Suspended Solid) concentration followed by Turbidity-TSS linear regression correlation.

Increased turbidity levels are clearly evident under the SRES A2 scenario, following more pronounced increased stream flows. Projected 75th percentile monthly turbidity values in year 2020 are expected to increase during May to November compared to the baseline, and in certain months, about 100%increase is noted. 60% of the time, year 2020 turbidity levels have indicated exceedance of the water quality standards set for the potable water as well the inland waters of Sri Lanka, which would lead to exert extra challenge on future drinking water production in Southern region of Sri Lanka.

ENGINEER, Vol. 48, No.01, pp. 61-70, 2015