A seasonal freshwater marsh formed from seasonal freshwater rivers and small permanent lakes, forming part of the Black Volta basin. This is a biodiversity rich area supporting several fish and bird species already decreasing in the Inner Niger Delta, such as the African bonytongue Heterotis niloticus, Senegal bichir Polypterus senegalus and freshwater rat-tail Gymnarchus niloticus. 20,978 individuals of 32 bird species were identified in 2009 with over 2% of the West African breeding population of the African pygmy-goose Nettapus auritus and purple heron Ardea purpurea, and 22,000 bird individuals in 2011. The site also supports IUCN Red-Listed hippopotamus Hippopotamus amphibius and African elephant Loxodonta africana. The rice fields are a good source of food and a spawning ground and nursery for fishes of the Sourou basin. It ensures general hydrological balance of the basin, flood control and groundwater recharge. The main human activities include rice farming, fishing, and wood harvesting.