is a reservoir area in the city of Agano, Niigata, Japan. The reservoir was created in 1639 during the Edo period of Japanese history. It is noted for its abundant and diverse bird life, and is an important overwintering grounds for Whooper swans and Tundra swans. The area received protection from the Japanese government as a wildlife refuge in 2005. On October 30, 2008, it was registered as a Ramsar site. Birds Whooper swan (October–March) Tundra swan (October–March) Northern pintail (October–March) Common pochard (October–March) Eastern spot-billed duck (all seasons) Plants Land Nelumbo nucifera white (July–August) Iris blue-purple (May) Aquatic Trapa natans var. japonica Phragmites Manchurian wild rice References Reservoirs in Japan Ramsar sites in Japan Tourist attractions in Niigata Prefecture Landforms of Niigata Prefecture Agano, Niigata