EYDAP uses raw water mainly from surface water resources (Marathonas, Yliki, Mornos, Evinos). From these reservoirs, only Yliki is natural, while others have been created by the construction of dams in the appropriate places in the respective Evinos river bed, Mornos river bed and Haradros (Marathon Dam). Into water sources used by EYDAP are also included and underground water resources which are exploited by 100 boreholes with total annual pumping capacity 70-125 million m3 of water per year.

Based on current operating conditions, EYDAP water resources can be divided into:

  • Main water source (Evinos, Mornos Lake)
  • Auxiliary water source (Yliki, Marathonas)
  • Backup water source (underground water resources)


Marathon Reservoir
Marathon Reservoir was created by the construction of a concrete dam at the intersection of the Charadros and Varnava Torrents. The reservoir operates as a backup source for the water supply system of the greater Attica region and as a primary regulating reservoir. Marathon Reservoir supplies water from the reservoirs of Mornos and Yliki, via Yliki Aqueduct and Mornos-Yliki Connecting Aqueduct.

Yliki Reservoir
The natural lake of Yliki is located at the Prefecture of Boeotia. It was joined in water supply system of Athens in order to meet the great needs of water consumption due to the population increase in Attica Region.
Yliki lake is situated on a lower altitude compared to Athens. For that reason, the lake water intake structures depend on the operation of various pump units of significant power capacity (both submerged and on - land). Its central pumping station is one of the largest in Europe. As Marathon Reservoir, Yliki Reservoir works as an auxiliary water source for emergencies

Mornos Reservoir
The construction of Mornos Dam (126 meters high) began in 1969. The repletion of the reservoir began in 1979 and all works were completed by 1981. The dam is located on the Mornos River and is one of the largest earthen dams in Europe.

Evinos Reservoir
The Evinos project was built in the River Evinos, near Agios Dimitrios at the Perfecture of Aetoloacarnania (Mountainous Nafpaktia), and included the construction of a dam and a reservoir as well as the construction of Evinos-Mornos Tunnel. The design and implementation of the project aimed at the strengthening of Mornos Reservoir from the neighbouring Evinos River.
The project on the Evinos began in 1992 with the construction of an earthen dam which was completed in 2001.

Evinos - Mornos Tunnel
Through the Evinos – Mornos Tunnel, the Evinos Reservoir waters are transported and channelled the Mornos reservoir to boost water reserves. The operation of the Tunnel is under pressure to provide 27 m3 of water per second. The Evinos-Mornos tunnel has a total length of 29,4 m and inner diameter of 3.5 m. The construction of the tunnel started in 1992 and completed in 2 years, which represents a great success.

Besides the 4 Reservoirs mentioned above, there are more than a hundred boreholes located in the prefectures of Attica and Boeotia that have backup role in water supply system. These boreholes can provide 800,000 m3 of water on a daily basis while their reinforcing role in water supply system is estimated at 70-125 million m3 of water per year. The boreholes are an auxiliary source of raw water and are to be used in the event of emergency. The total wattage of boreholes operation amounts to 25,000 HP.