In order to maintain the continuity of wetland ecosystems, an 'ecological flow' is maintained in the river ecosystems downstream of the dams. Maintaining this minimum required flow is essential in accordance with legislation, environmental conditions and current international trends in environmental management of reservoirs.

At the Marathon dam, the necessary actions have already been undertaken in order to increase the residual flow downstream of the dam to 25 l/sec. according to the recent TEPEM (Technical Environmental Study) implemented by EYDAP.

The river ecosystem downstream of the Mornos dam is in good condition, due to the continuous flow of surface water in the riverbed. EYDAP has completed the systematic monitoring of the ecological and chemical status of the river ecosystem by implementing a three-year program of hydromorphological, physicochemical, biological and chemical measurements, in accordance with the specifications of the Water Framework Directive 2000/60/EU and the Water Management Plan YD04, which was required by the Technical and Environmental Study (TEPEM) of the Mornos Dam prepared by EYDAP SA. The above monitoring showed that the river ecosystem downstream of the Mornos dam is in good ecological and chemical condition.

In Evinos River, the newest reservoir, an "ecological flow" of 1 m3/sec is planned. Consequently, the riparian ecosystems downstream of the dam retain their profile and significant biodiversity.