Koshi Tappu lies between the coordinates of 26° 56′ -26° 40′ and 85° 56′-87° 04′  in the floodplains of the Koshi river. It covers an area of 348 sq.km, including the buffer zone of 173 sq.km. It was designated as a Wildlife Reserve in 1976 and is under the jurisdiction of the Department of National Parks and Wildlife Conservation.

Some characteristic features:

• It is the first Ramsar site of Nepal, designated in 1987.
• The Koshi Tappu Wildlife Reserve safeguards the pristine riparian wetlands, cattail fields, mudflats, grasslands, forests, marshes and swamps, lakes and ponds, and excavated ponds. Some of the flagship species found in the reserve are the globally threatened wild water buffalo called ‘arna’ in Nepal (Bubalus bubalis arnee), the Gangetic dolphin (Platanista gangetica) and endemic fish species (Barilius jalkapoorei and Pseudeutropius murius). Other globally threatened fauna include nilgai, smooth-coated otter, and red-crowned roof turtle.
• Koshi Tappu is also one of the Important Bird Areas (IBAs) of Nepal. It is a haven for birds such as swamp francolin (Francolinus gularis), Baer’s pochard (Aythya baeri), pallas’s fish eagle (Haliaeetus leucoryphus), greater spotted eagle (Aquila clanga), lesser adjutant (Leptoptilos javanicus) and spot-billed pelican (Pelecanus philippensis).
• There are about 215 settlements in the vicinity of the wetland. The inhabitants depend on the wetland for irrigation, livestock grazing, fisheries, and food production, and obtain construction materials from the forests.
• Major threats are feral cattle grazing, flooding and siltation, wildlife depredation, and illicit trade.