The lake and marsh of Réghaïa are found at the estuary of the Réghaïa wadi (river), the mouth of which has been blocked by a sand ridge. 600 metres inland, an artificial barrier keeps water permanently in the marshes, sustaining its reeds and rushes. The marsh is the last vestige of the old Mitidja alluvial plain and is the only wetland near Algiers to survive the drainage works of the colonial era. It faces the Mediterranean, and includes a small island called Agueli or Bounettah which lies a kilometre offshore, and the surrounding waters. It is important for migratory birds arriving from the Mediterranean Sea and from the Sahara Desert. In spite of its declining size, the lake maintains a wealth and diversity of rare nesting birds as well as wintering migrants. It shelters more than 203 waterbird species, including the ferruginous duck Aythya nyroca, the marbled teal Marmaronetta angustirostris and the white-headed duck Oxyura leucocephala. The immediate surroundings consist of fallow fields and maquis featuring wild olive and mastic shrubs as well as a few eucalyptus groves. The lake provides irrigation for 1,200 hectares of arable land, and the beaches attract many visitors during summer. The Centre Cynégétique de Réghaïa organizes World Wetlands Day exhibitions.