The impact of agricultural pollutants in six drinking water reservoirs

Water is supplied in the Greater Istanbul Metropolitan Area from the surfac e water of six main reservoirs. The present land use in the catchment areas of the reservoirs indicates that the area devoted to agricultural activiti es and to forests and meadows varies between 73 and 97% and that only a min or percentage, 1-26%, is devoted to settlements and industries. In contrast to the land use profile, the current environmental evaluation of the catch ment areas reveals that point sources dominate over diffuse sources. Howeve r, this trend is expected to be reversed in the near future, making diffuse sources and control of fertilizers and pesticides the most significant iss ue. Pollutant loads regarding pesticides and fertilizers are calculated fro m unit loads based on area. These pollutants are observed to have a negativ e impact on water quality in terms of eutrophication and toxicity. In this paper, the status of fertilizers and pesticides are addressed and some prot ective measures for reducing the impact of agricultural pollutants in the r eservoirs are recommended. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.