The Lake Tazawa (田 沢 湖jap, Tazawa -ko ) is a caldera lake in Akita prefecture in northern Japan. He is with 423.4 meters is the deepest lake in Japan. Because of its depth, it never freezes even in hard winters.
In the past boasted of its clear water lake that could compete with the Lake Mashu in Hokkaidō. However, the water was polluted by the construction of a dam for a hydroelectric power plant in 1940 and the effluents from a thermal source. This led to the disappearance of Kunimasu (Oncorhynchus nerka kawamurae ), a Fischtaxon, which was believed that it was endemic in Lake Tazawa. 2010, however, a population in Saiko Lake near the Fuji was rediscovered.
The former municipality Tazawako ( a district of Senboku since 2005) is named after the lake. JR East maintains a Tazawako - line and once there was an express train from Morioka to Akita Tazawa, until it was replaced by the Akita Shinkansen in 1997.