Today, Attica is supplied mainly by the Mornos and Evinos reservoirs or, alternatively, by the Yliki reservoir. The Marathon reservoir is connected to the above main reservoirs through conjunctive aqueducts and is used both as a reservoir for the overhaul of the external water supply system of Attica and as a project ensuring the uninterrupted distribution of water, due to its proximity to the city of Athens. The construction of the Marathon reservoir is such that ensures sustainable water supply in line with the current reservoir sustainability practices with the purpose of preserving the aquatic ecosystems downstream the Dam.