Point and Diffuse Sources of Pollution and Surface Water Quality in Marmara Basin of Turkey

Abstract

Marmara Basin includes the areas in Turkey with the densest industrialization and population. Surface waters are threatened particularly by point sources originating from municipalities and industries, although most of them are discharged to the sea. Therefore quality of existing surface waters and the sources of pollution are of great interest. Watershed protection action plan has recently been prepared for the basin. A detailed study on calculation of pollution loads was one of the most important outputs of the project. For this purpose, pollution loads based on chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP) were calculated. Water quality classes of surface waters were determined based on Turkish regulations using the data obtained by State Hydraulic Works (DSI). The relationship between point and diffuse pollution sources and water quality was examined. According to the obtained data most of the creeks around Istanbul are polluted by point sources originating from the highly populated and industrialized city of Istanbul and its suburbs. On the other hand, the creeks which feed Iznik Lake and downstream of Gonen and Biga Creeks are polluted by diffuse sources as well as point sources. Results showed that point-source pollution due to untreated or treated domestic and industrial wastewaters is mainly responsible from pollution in rivers and lakes of the Marmara Basin. Besides in the less populated areas, diffuse-source pollution originating from agriculture and livestock breeding is responsible from deterioration of surface water quality.