Behavior and Loading of Suspended Sediment and Nutrients from River Basins in the Hilly Catena Under Intensive Agriculture Cropping: A Case Study in Upper Kotmale Basin in Sri Lanka

Suspended matter and nutrient are major factors for water pollution studies and this study is focused on behavior and loading of suspended sediment and nutrient in Upper Kotmale Basin (UKB). Nanu Oya, Dambagasthalawa Oya and Agra Oya are three major streams fed by Kotmale Oya proper in UKB. Eight sampling locations were selected considering all major rivers and eight months samples were collected on monthly basis. Data analysis is used cluster analysis and descriptive statistic was used for analysis of nutrient and suspended sediment loading in streams. Results reveal that, highest nutrient loads bring by Nanu Oya and calculated mean daily nutrient loads namely; ammonia-N, nitrite-N, nitrate-N, and dissolve phosphate were found to be in Agra Oya; 33.6 kg/day, 2.3 kg/day, 383.1 kg/day and 48.2 kg/day, Nanu Oya; 64.1 kg/day, 9.1 kg/day, 1459.1 kg/day & 530.4 kg/day and Dabagasthalawa Oya; 19.5 kg/day, 1.7 kg/day, 310.6 kg/day & 109.6 kg/day respectively. Also, the calculated highest suspended sediment (SS) load were found to be in Agra Oya; 4839 kg/day, Nanu Oya; 22083 kg/day and Dambagasthalawa Oya; 5843 kg/day respectively. Therefore, Nanu Oya contribute highest SS and nutrient load to Kotmale Oya proper, because of landuse change. This scenario is vulnerable to deterioration of the water quality and aquatic environment in downstream and Kotmale Oya proper. DOI: http://dx.doi.org/10.4038/jepsl.v2i2.6327 Journal of Environmental Professionals Sri Lanka, Vol. 2 No. 2 2013, 13-31