The studies of the ecological flow regimes for various streams downstream of the dams of Vilar, Caldeirão, Açude de Trinta Fronhas and Raiva aimed at determining the minimum water flow possible in order to conserve and maintain the natural aquatic ecosystems, the production of species with special interest, the aesthetic aspects of the landscape and other aspects of scientific or cultural interest.

The study comprised the surveys necessary to identify the hydroelectric harnessing energy and ecological characteristics of the downstream sections, namely the water regime of the basins and ecosystems, the reliability and limitations of the applied methods, the dimensioning of infrastructures and water needs inherent to the harnessing objectives.

In determining the ecological flow regimes various methods are applied and the results obtained compared, in order to define the most suitable ecological flow regime.