A long‐term management plan for a watershed in a world metropolis – Istanbul

Ömerli reservoir is the major reservoir of Istanbul in terms of water supply potential. However, rapid population increase, unplanned and illegal housing, irrelevant industries and motorways passing through the protection zones of the catchment area, together with insufficient infrastructure, cause the water quality of the reservoir to tend towards the eutrophic stage from the mesotrophic stage parallel to the land use profile. In order to achieve a long‐term water supply from the reservoir and to arrive at sanitary solutions, new land use plans should be developed. Therefore, the key idea of this paper is to develop a convenient protection strategy to keep the reservoir from further deterioration, in light of the guidelines of a new land use plan, and to allow the watershed to be used in accordance with the tendencies of society in a controlled manner, so as to maintain the sustainability of the reservoir for drinking water supply and to assure continuing control by implementing economic sanctions.