Determination and control of diffuse pollutants arising from watersheds - A case study from Turkey

This study presents the estimated current diffuse pollution profile of Aras watershed located at the north-eastern part of the country representing an under-populated and less industrialized watershed. In the estimation of diffuse pollutants, such as those arising from agricultural land, livestock breeding, forests, meadows and pasture, dumpsite leachate, septic tank effluents and atmospheric deposition; the major factors to be determined are the areal data of each land-use activity as well as the urban and rural population values. The paper refers to the distribution of these major diffuse pollutants at each of the sharing provinces, at watershed scale; the major diffuse N contribution is manure with 33%, followed by rural run-off and run-off from meadows and pasture with the equal share of 22%. Excess fertilizers contribute 12% to diffuse N pollution whereas the share of septic tank effluents is 3%. Unlike N loads, diffuse P loads arise from excess commercial fertilizers by 40%, followed by manure with 30%. Rural run-off contributes with 18% and septic tank outflow with 5%. The future loads for 2028 and 2039 are also estimated, and 30-40% decrease is foreseen through the stepwise application of ecological agriculture and animal breeding. Another control measure proposed depends on the installation of sanitary landfills and constructing more sewer systems to both urban and rural sites. The basic aim of this study was to put forth a guideline for identification of diffuse sources of pollutants which will be followed in determining such loads in the developing countries.