Lake Inbanuma is a natural fresh water lake located in the northwestern part of Chiba Pref. The total surface area of the lake is 11.5 square kilometers, spanning the cities of Yachiyo, Sakura and Narita and the village of Inba. It is the largest lake in the prefecture. About 1,000 years ago, it was connected with Lake Teganuma and Lake Kasumigaura and formed a vast wetland. Due to the deposition of mud and sand inflowing from the upstream, Lake Inbanuma itself is presently divided into two parts; the west lake and the north lake, which are connected by a canal.
In the Edo period (1603-1868), when the course of the Tone River was moved to the east, the water influx into Lake Inbanuma increased in volume and floods occurred frequently. Several repair works including the Tenmei Repair Work by Tanuma Okitsugu and the Inbanuma Waterway Works by Torii Tadateru were given but resulted in failure. The fight with water continued till the eras after the Meiji period. In 1965, the Development Work of Lake Inbanuma was completed and no flood has occurred since then. Now Lake Inbanuma is an important water source, which supplies water for agriculture and industry to the surrounding areas as well as drinking water to the cities of Chiba, Funabashi and Narashino.