| Summary: |
Agriculture is among the main land-use types in the Istanbul catchment areas occupying almost 40% of the total surface area of the city. This study aimed to determine the agricultural land-cover changes in 7 main watersheds of Istanbul between 1987 and 2007 in order to evaluate the risk of agricultural pollution in water resources. Two Landsat images from 1987 and 2007 were classified using the maximum likelihood supervised classification method and utilizing ERDAS IMAGINE 9.1. The study revealed that agricultural areas have declined in all watersheds between 2.4-77.8% from 1987 to 2007. Around 8,000 hectares of agricultural land was lost in the entire study area between 1987-2007, corresponding to 9.2% of the total agricultural land. The study also revealed that agricultural activities constitute a significant risk for water quality, especially in the Büyükçekmece and Sazlıdere watersheds where agriculture accounted for 66.9% and 40.3%, respectively, of land-use within the watersheds in 2007. In the other 5 watersheds of Istanbul, agricultural areas occupy between 2-12.3% and do not constitute a great risk. Overall, the study revealed that agricultural areas account for around 24% of the total surface area in the 7 major watersheds of Istanbul today. Although point sources still dominate over non-point sources in the pollution of the watersheds of the city, non-point sources, especially agricultural activities, are expected to become more significant after the point sources of pollution have been controlled in Istanbul. Therefore, agricultural activities should be accorded more importance in or-der to have a sustainable and effective plan for the protection of water resources from point and non-point sources of pollution in Istanbul. |