Büyükçekmece Watershed is used as drinking water re- sources, located (41006’89’’N, 28055’65’’E) approx- imately 30 km to the southwest of Istanbul (Figure 1). The lake’s bar was reinforced in 1988 by a dam. The area of the lake is 28.47 km2 and lies in a 620 km2 watershed. Büyükçekmece Lake is 7 km long and 2 km wide. The maximum depth is 8.6m following deepening works car- ried out by the Ministry of Environment and Forestry of Turkey. The largest stream feeding the lake is Karasu Stream, which is connected with other streams. Others are Hamza Stream, Ahlat Stream, Tahtaköprü Stream and Beylikçayı Stream.