It is situated along the mighty Koshi River in southeastern Nepal north of the Koshi Barrage. Koshi is one of three major rivers of Nepal and the reserve is located in an area as it descends to the Terai from the hills. It is 10km wide and 17km long and stretches along both sides of the river. It does not have such wildlife as rhinos or tigers but is best known for water buffaloes- Babulus Arnee (called Arna in Nepali). It is actually supposed to be the best place in Nepal for watching migratory birds which migrate across the main Himalayan range. There are supposed to be 300 species in the area. Wildlife in the area includes spotted deer, wild boar and bison. There are also crocodiles (both mugger and gharial) and dolphins in the river. It is spread in the areaof 175 sq.km.