General Directorate Of State Hydraulic Works


The Geographical Structure of the Region

 The most interesting feature of the 14 th Regional Directorate of the State Hydraulic Work is that its mission area is on both Asia and Europe. The İstanbul Bosphorus that separates the Asia continent and Europe continent also separates the project area into two parts.

At the west side (Europe), the most significant geographic structures are Haliç which is a natural harbor, Büyükçekmece and Küçükçekmece Lakes and small drainage fields.

At the east side ( Asia), the topographic structure changes according to the hill and mountain formations. The mountain formations in the region increases to 2378 meters with Köroğlu Mountain at the east and 1031 meters with Istıranca Mountains at the west.

The Mission Area and Districts Covered

14 th Regional Directorate of State Hydraulic Works (DSİ 14 th) is mainly established for supplying water to İstanbul. On the other hand, since Gebze, a distinct of Kocaeli, is in the water distribution system of İstanbul, it is also in the mission area of Dsi 14 th.

The mission area of the DSİ 14 th, which is reestablished by the decree of “Council of Ministers” dated 12.06.1993 with reference no 93/4539 and dated 20.12.1993 with reference no 93/5207, is expanded by including the cities Bolu, Sakarya, Kocaeli, Tekirdağ and Kırklareli only on the studies of the Greater İstanbul Water Supply Project. Thus, the mission area of the DSİ 14 th covers 6 cities and 37,974 km 2 area in the current position.

Climate in the Region


Marmara and West Blacksea climates are effective in the region. In these temperate climates, summer is hot and with few rain, winter is temperate and rainy. Topographic structure, the lakes and dams in the region effects the climate. Because the mountains on the seaside do not let the rain clouds to move in, the seaside is more rainy when compared to the inner areas of the region. The amount of rain in the region is between 500mm-1000mm per year. Average amount of rain is 781mm per year. 85% of the total amount of rain falls down between September and May.

Average temperatures in the region are between 6,3 ° C-13 ° C. The temperatures rarely falls down below 0 ° C. Average temperature in January is 5,4 ° C and 23,4 ° C in August. Yearly average temperature is 14 ° C in İstanbul.

The effective wind blows from north and northeast side but the direction of the wind may change according to the weather conditions and seasons during the year. In winter northeast, in summer west-southwest, in summer north-northwest and in fall southwest-northwest are the effective wind directions in İstanbul.

Population and the Surface Area of the Cities


Surface Area(km2)








































Melen System is developed for covering the long term water demand of İstanbul. By supplying 268 million m 3 water at the first stage and 1,180 billion m 3 water at the third stage the water demand of the city until the year 2040, will be met .

At the Stage I. of the project, water taken by the regulator constructed on the Melen River, will be transferred to Melen Header Tank from Melen Pump Station by a steel rising main that is 1,75 km. long. The water in the Melen Header tank will be transferred to Alaçalı Dam Resevoir by the steel pipeline ( 129,6 km long) and Şile-Alaçalı Tunnel ( 3,8 km long). The process will continue by transferring the water from the Alaçalı Dam to the Cumhuriyet Water Treatment Plant by Alaçalı-Ömerli-Hamidiye Tunnel ( 8,00 km long) and steel pipeline ( 8,9 km long) and by gravity main. If it is needed, the excess water in the Melen System will be transferred to Ömerli Dam by the connection structure between Hamidiye Tunnel and Ömerli Dam by gravity main. The capacity of Cumhuriyet Water Treatment Plant will be 720 000 m 3/day. One of the main objectives of the project is refining the raw water in order to serve for the public usage by the help of modern technology, The quality of the water will met the standards of the European Union.

Water refined in Cumhuriyet Water Treatment Plant will be pumped to Cumhuriyet Header Tank from Cumhuriyet Pump Station by the rising main that is 3,9 km long. This water will be transferred to Kağıthane Water Distribution Center, located in the European side, by steel pipelines and tunnels and by gravity main.

The Bosphorus Tunnel will be constructed at 5,551 meters long and it will be 135 meters under the sea surface.

At the first stage of the project 157 meters long-steel pipes will be used. Total length of the tunnels in the system is 25 kilometers.

At the second stage of the project Melen Dam will be constructed, the units will be added to pump stations and water treatment works and the second pipeline will be laid down.

At the third stage of the project units will be added to pump stations and water treatment works and the third pipe line will be laid down.

Total investment cost of the Project Stage I is estimated as 1,181 billion US dollars and 900 million US dollars is received from Japan in two portions. The interest rates of the loan is 3% for the first portion of the loan and 2,5% for the second portion of the loan. Loan does not cover the resettlement and expropriation expenses. As the result of the tendering, it is determined that the tender prices of all construction and manufacturing work will be 530 million US dollars. According to the Liquidation Written Decree published in the Official Gazette dated 18.08.2001, CP4 and CP7 are liquidated.

The engineering and consulting services of the Melen System is tendered to a consortium formed by eight consulting firms in 26.06.1995. According to the contract, consulting firm have to finish its all obligations in 72 months starting from April 18 th 1996. The deadline for consulting services is May 31 st 2004. The eight consulting firms are as follows:

Nippon Koei Co., Ltd. of Japan as the leading company (NK)

Sir Alexander Gibb & Partners Limited of United Kingdom (GIBB)

Mott McDonald Limited of United Kingdom (MML)

SETAN Engineering Company, Ltd. of Türkiye

SU-YAPI Engineering and Consulting Inc. Of Türkiye

TEMELSU International Engineering Services Inc. of Türkiye

DAPTA Engineers and Consultants Ltd. of Türkiye

SİAL Geoscience Investigation and Consulting Ltd. Co. Of Türkiye

Melen Project is formed of 11 work units. 7 of them are construction works, 3 of them are manufacturing works and one of them is energy works. Alaçalı Dam and Tunnel Works (CP4), Bosphorus Tunnels (CP7) and Energy Supply Works (CP11) are in tendering stage in the current position. Tendering studies are made by Department of Water Supply and Sewerage.


 Yeşilçay System is planned to cover the water demand of the city by transferring the minimum movements in Göksu and Çanak Creeks in Ağva-Şile. The aim of the system is not to face any lack of water problem until the Melen Project is completed.

At the first stage, water collected by İsaköy and Sungurlu Regulators, will be transferred to Surge Tank by steel rising main and then will be transferred to Emirli Yavuz Selim Water Treatment Plant. With this system 145 million m 3 water will be added to İstanbul Water System and water demand of 1,5 million people will be met. After İsaköy and Sungurlu Dams are built, the amount of water that can be distributed to the city will be 335 hm 3/year.

The construction of the pipeline between Darlık Tunnel- Water Treatment Plant is completed and the water taken from Darlık Dam-Lake reaches to the Water Treatment Plant by passing from 3000mm. diameter steel and prestressed concrete cylinder (PCC) pipeline and Kömürlük Tunnel and Ömerli Aqueduct. The water refined here will be ready for the usage.

The total cost of Yeşilçay System is 271 million US dollars and 145 million dollars of this amount is received from Kuwait Fund for Economic Development (KFAED). The interest rate of the loan is 4,5% and the date of maturity is 20 years.(no payment will be made in first 7 years)



Adress: Libadiye Cad . K.Çamlıca -ÜSKÜDAR 34 996 / İSTANBUL-TURKEY
Phone: 90 216 325 63 20 Pbx Fax: 90 216 325 63 41




General Directorate Of State Hydraulic Works