Sedimentary characteristics and status of water quality in Polwatta river and Weligama bay in Sri Lanka

The Weligama Bay is a one of the rocky shorelines in the coastline of Sri Lanka and Polwatta River is the major river which enters to south part of the Bay. The study objectives were to find out the sedimentary characteristic, and water quality status in Polwatta River and Weligama bay. Results indicated that, mean water temperature, pH, NO3- -N, PO4-3, and NH4- -N, in Polwatta River and Weligama Bay are 28.20 C ± 1.8, 6.7 ± 0.3, 0.11 ± 0.04 mg/l, 0.73 ± 0.1 mg/l, 0.46 ± 0.1 mg/l and 28.5 ± 1.00 C, 7.57 ± 0.1, 0.51 ± 0.04 mg/l, 0.40 ± 0.1mg/l and 0.20 ± 0.1 mg/l in respectively. The, mean suspended sediment concentrations were recorded in Polwatta River was 241.1 ± 150 mg/l. However, mean gravel, sand and silt percentages in the Weligama Bay are 1.42 ± 1.4, 96.33 ± 0.5 and 2.25 ± 0.3 in respectively. The study of current patterns shows the direction is west to east of the Bay and surface current is 12 cm/s. Results reveal that, nutrients in the Polwatta River and Weligama Bay are within the acceptable limits published by Sri Lanka Standard Institute and draft CEA ambient water quality standard. Also, high concentration of suspended sediment load coming through the Polwatta River during south-west monsoon period and part of that remain in the estuary and other discharge to the Bay. Also, due to currents sediment traverse to southern part of the coast in Weligama. DOI: http://dx.doi.org/10.4038/jepsl.v2i1.5745 Journal of Environmental Professionals Sri Lanka Vol.2(1) 2013 38-5