Ömerli Barajı

Ömerli Dam is a reservoir built on the Riva Stream in the interior of Istanbul's Asian side to supply drinking water. According to the records of the State Hydraulic Works (DSİ), construction began in 1968 and ended in 1972; İSKİ, the city's water utility, says the dam went into service in 1972. According to İSKİ, its yearly capacity of 220 million cubic metres makes it Istanbul's largest water source. Almost the whole of the Asian side takes its water from this dam, and the water is treated at the Ömerli Drinking Water Treatment Plants before reaching the city. Through the supply lines between Salacak and Sarayburnu, up to 370 thousand cubic metres a day can also be sent to the European side. The body of the dam is an earth fill, and DSİ records give its height above the stream bed as 53 metres; Wikipedia gives the figure as 52 metres. At normal water level the lake covers about 23 square kilometres and holds around 386 million cubic metres of water. The catchment that feeds the dam is a large area of 621 square kilometres. The Riva Stream rises near the village of Tepecik in Gebze, Kocaeli, and after the dam it flows through forested valleys to reach the Black Sea at Riva in Beykoz. The lake takes its name from Ömerli on its shore; Ömerli is now a neighbourhood of Çekmeköy whose edge runs straight down to the reservoir. Ömerli was a village attached to Beykoz between 1928 and 1989, became a small town in 1996 and, when its municipality was abolished in 2009, turned into one of Çekmeköy's neighbourhoods. The district of Çekmeköy itself was created in the same year by merging the municipalities of Ömerli, Alemdağ and Taşdelen. Below the dam the Riva Stream passes settlements such as Koçullu, Ömerli, Sırapınar and Hüseyinli, and most of this second stretch is covered with forest. The right way to visit Ömerli is to enjoy it as a lake view from the roads along the shore and from the areas where access is allowed. Because this is a drinking water reservoir, the dam body, the intake structures and the treatment plants are not public sightseeing areas. The draft protection plan for the Ömerli reservoir basin published by the Ministry of Agriculture and Forestry bans throwing any kind of waste into the lake. According to the same draft, net fishing and fish farming are not allowed on the lake, and boats running on fuel are not permitted either. Water sports such as rowing and sailing can only be organised by public bodies or sports clubs with permission from the administration. Even these activities are not allowed closer than 300 metres to the drinking water intake. So do not go into the water, do not light fires on the shore and always take your rubbish back with you. Together with its catchment, the lake sits in the middle of a wide forested area, and wooded slopes run down to the water on its shores. The draft protection plan shows that the basin extends into the districts of Ataşehir, Çekmeköy, Kartal, Maltepe, Pendik, Sancaktepe, Sultanbeyli, Şile and Tuzla. Protecting the forests in the basin and not letting them shrink is one of the plan's core principles. The calm, wide surface of the lake reflects the colours of the sky at sunrise and sunset; these two hours are the most rewarding for photographs. While looking from the shore, notice how the forest cover on the opposite slopes changes colour with the season. The story of the dam is an important link in Istanbul's modern water history. According to İSKİ, the first dam on the Asian side was built on the Elmalı Stream in 1893 by the Üsküdar-Kadıköy Water Company; Ömerli came into service about eighty years later on a far larger scale. Today other sources support Ömerli, such as the Darlık Dam in Şile and the regulators of the Yeşilçay project. The Darlık Dam, which came into service in 1989, has a yearly capacity of 97 million cubic metres, and its water is treated at the plants in Emirli. The draft protection plan defines the lake's maximum water level as 62 metres above sea level and measures the protection zones from this line. The lake is far from the city centre and has no direct rail link; if you are coming by public transport, check current bus routes with İETT. Those coming by car can use the village and neighbourhood roads along the shore, but drive slowly on the forest roads and park only where it is allowed. Bring water, a windbreaker and comfortable shoes; there is not shade everywhere on the shore. Combining the dam with nearby Polonezköy or Aydos Castle on the same day is a good plan for getting to know the eastern part of the Asian side.