The Legii Lake and Valley area has been a protected nature reserve for the conservation of wetland bird species since 1966, established in order to preserve one of the last remaining natural wetlands in the Fizes Basin. Nevertheless, hydro-technical constructions in the area resulted in the gradual shrinking of the lake. In present days, the entire area is covered by reed. GIS techniques were used in order to estimate the area and depth of the lake after ecological restoration of the wetland. The calculations were based on a DEM (Digital Elevation Model), obtained using contours extracted from the topographical maps (1:25000 scale). Historical maps of the area were also used in order to determine the evolution of the river system and slopes to evaluate the consequences of human intervention in the area. The result was a complex model that allows multiple scenario evaluation. The model was used to predict the changes in the ecosystem and how suitable the area would became for protected bird species.