About İSKİ


Statistics on Istanbul

Population Served : 15 million 519 thousand
Total Area of Service : 5 thousand 461 km2
Number of Subscribers :
6.6 million
Length of Water Network : 19 thousand 577 km
Length of Transmission Lines : 2 thousand 847 km
Yield of Water Resources : 1 billion 653 million m³/year
Average daily water supply : 3 million m³/day
Number of Potable Water Treatment Plants : 21
Capacity of Potable Water Treatment Plants : 4 million 352 thousand 220 m³/day
Number of Water Storage Tanks : 152
Volume of Water Storage Tanks : 1 million 567 thousand 080 m³
Total length of sewers : 16 thousand 515 km
Length of Collector Lines : 1197 km
Length of Tunnels : 201 km
Number of Wastewater Treatment Plants : 88
Capacity of Wastewater Treatment Plants : 5 million 811 thousand 990 m³/day

Administrative Structure

Founded in 1981 with the launch of İSKİ Law no. 2560, İSKİ is a public utility of Istanbul Metropolitan Municipality with an independent budget. The managerial board of the administration where the Mayor of Istanbul is the Board Chairman is the Metropolitan Municipality Council. The General Director of İSKİ is elected upon the proposal of the Metropolitan Municipality Mayor and approved by the Minister of Interior Affairs. The General Director of İSKİ also acts as the Vice Chair of the Management Board which also includes 4 members including a senior Deputy General Director. Two inspectors elected by the İSKİ General Board (Municipal Assembly) conduct inspection services.
The administration includes 5 Deputy General Director Offices, Department of Inspection Committee, Legal Advisor’s Office, Internal Auditing Unit, 19 Departments and 96 Directorates. A total of 6,626 staff includes 3,958 workers and 2,668 officers with a majority of technical background.
A great majority of the income of the administration is from the water sales. Most of the investments are conducted through this income from water sales.
To receive İSKİ’s services, water and wastewater subscription is required through a contract with İSKİ. Water consumption is identified and measured via mechanical or card meters. Contracts are classified according to the consumer groups of households, offices, administrations, industrial locations, village settlements and offices as well as municipal buildings. İSKİ currently has 4 million 901 thousand 405 subscribers. 

Water Management
98 % of water resources in İstanbul are surface water resources. Water from rainfall is collected in dams and natural lakes, then transferred to treatment plants via weirs. There are 17 surface water resources in İstanbul, including 1 natural lake, 8 dams and 7 weirs. Furthermore, there are 145 potable water wells with an annual capacity of 37 million 320 thousand m3 feeding the regions of Silivri and Çatalca.
The annual yield of potable water resources is 1 billion 353 million m3.
Water catchment basins reach up to 6.157 km2 together with the Melen basin.
60% of water resources are on the Asian side with 40% of population, while 40% of the water is on the European side with 60% of the population.
Water collected in the resources is delivered to potable water treatment plants via transmission lines of 3m in diameter. Reaching a total length of 2.390 km, 823 km of the transmission lines is steel, 598 iron ductile, 20 km polyethylene and the rest (in tunnel, channel and galleries) is made of other materials. The transmission lines can resist a maximum pressure of 40 atü.
The rough geography and distance of water resources to the city in İstanbul brings about a large energy requirement. In every stage between the water resource and house taps, pumping systems were installed to enable pressure supply. Pumps of various capacities in 115 pumping stations all around İstanbul provide water to all corners of the city. The installed capacity of all potable water pumping stations is 308.805 kVA and the annual energy consumption is on average 757 million 805 thousand 995 kWh.
Raw water in the potable water resources reach to the water treatment plants via transmission lines for the required treatment processes. There are 13 potable water treatment plants in İstanbul. Ozoning system is adopted in these plans that have a total capacity of 4 million 287 thousand 600 m3/day to enable provision of water with potable standards.
There are 114 water storage tanks of various sizes in different parts of İstanbul. Constructed to provide water consumption balance, to save energy, to minimize water cuts occurring due to breakdowns and energy cuts, the total capacity of these tanks is 1 million 488 thousand 580 m3.
Upon treatment, the water is supplied to the people in İstanbul via the transmission lines, potable water network in the distribution system. The potable water network is made of ductile iron pipes. The length of this pipe type selected due to its resistant, leak-proof and long-lasting aspects is 18 thousand 496 km.

Laboratory services
The quality of water treated at potable water treatment plants is analyzed at the laboratories in the same plants. Starting from the entry of raw water into the plant through the whole treatment process, the analyses conducted provide continuous monitoring of the quality of water supplied to the potable water distribution system. Over 80 parameters, including chemical, bacteriological and aesthetic ones, are monitored in the process. Furthermore, an average of 150-200 samples are taken from points where the water meets the residents of Istanbul in regions fed by each distribution system and analyzed in the labs. The results of these analyses are accessible monthly over the web page of İSKİ.

The whole potable water system of İstanbul is managed via the central command system called SCADA. All data on occupancy rate of water resources, rainfall, pressure values in potable water lines, water value in storage tanks are transferred instantly to the center, which can directly address to the system.
Wastewater Management
The used water that becomes wastewater is collected via a wastewater network of 14,990 km in length. Concrete pipes are the main material of the wastewater network lines. Wastewater is transferred to collector and tunnels through the network. The length of the collectors with a diameter of 2,20 m is 971 km. The collector lines are made up of concrete pipes resisting to corrosion and with high durability. In locations where open dig is not possible due to traffic density, ground conditions, regional geographical aspects, wastewater lines are dug via tunnel methods. A total of 147 km tunnels exist with a diameter of 3 m. Almost all of the coasts in İstanbul have been laid with wastewater collectors and tunnels. Robot technologies are used for the repair and maintenance works of the lines. Any blockage in the wastewater lines can be identified and cleaned by the camera robots and the breakdowns are fixed with no-dig coating, enabling longer pipe use.
Wastewater collected through collectors and tunnels is delivered to wastewater treatment plants. There are 67 wastewater treatment plants with different capacities planned in line with the requirements of the basin it serves within İstanbul. Considering the dynamic structure of the Bosphorus, the Bosphorus coasts were installed with primarily pre-treatment plants while biological and advance biological treatment processes were selected for locations along Marmara Sea. The total capacity of the wastewater treatment plants 5 million 585 thousand 465 m3/day.

Part of the outlet water from advance biological wastewater treatment plants is used for the irrigation of recreational areas and industrial water upon the final disinfection process. A significant amount of the energy required for the process of treatment plants is obtained via wastewater as well.