Istanbul has administrative, social and economic, drinking water problems. The forest areas of Istanbul are more important to drinking water than any other of the forest's activities, because most of the drinking water dams are located in forest areas. This study is aimed at determining the differences between past and present forestry applications concerning drinking water production in Istanbul for a 600 year period. The level of future drinking water problems in Istanbul was also estimated. Using descriptive analysis method similarities and differences between past and present forestry applications in producing drinking water were identified. Furthermore, the trend of Istanbul's water demand and supply for the 2010 and 2030 term was also predicted with a scenario. This study indicates that Istanbul city has historically experienced drinking water and forest resources shortages. In the past administrators were very keen to conserve forest areas and drinking water resources for the city. Various regulations to protect and improve the utilization of water resources have been created throughout the history of Istanbul. These measures today are not as effective as they once were which causes exploitation and destruction of water resources.