They also serve as an important natural purification system to protect the lake from water pollution and entrophieation which are currently reaching a serious state. Since 1995 the Environment Agency has commenced setting up a Waterfowl and Wetland Center in Biwa-ko. Sakata was formed in the hollow of a dune. The lake water is supplied from underground water of the dune. Many waterfowls such as Bewick's Swan, Whooper Swans, Bean Goose, White-fronted Goose and wild ducks visit there for wintering.
Marshes surrounding the lakeside provide a confortable environment for waterfowls.
In addition, the food condition is very suitable for waterfowls, because the location is about 2km inside the Japan Sea and near vast rice paddies area. In FY 1996, the Environment Agency will start to construct the Waterfowls and Wetland Center in Sakata as a base for the scientific research and conservation education.