| Lake Inawashiro 猪苗代湖 | |
| Location: | Fukushima Prefecture |
| Coords: | 37.4747°N 140.0936°W |
| Type: | tectonic lake |
| Outflow: | Nippashi River |
| Basin Countries: | Japan |
| Area: | 103.3km2 |
| Depth: | 51.5m (169feet) |
| Max-Depth: | 94.6m (310.4feet) |
| Volume: | 5.4km3 |
| Shore: | 49km (30miles) |
| Elevation: | 514m (1,686feet) |
| Islands: | Okinajima |
| Pushpin Map: | Japan |
| Pushpin Map Alt: | Location of Lake Inawashiro in Japan. |
is the fourth-largest lake in Japan,[1] located in central Fukushima Prefecture, south of Mount Bandai. It is also known as the . The lake is located within the borders of Bandai-Asahi National Park. It is a surface area of 104sqkm, circumference of 63km (39miles), depth of 94m (308feet) and is located at an altitude of 514m (1,686feet).[2] In winter swans migrate to the beaches of the lake and stay there until spring.
Lake Inawashiro was formed some 30–40,000 years ago when a tectonic depression was dammed by a major eruption and pyroclastic flow from Mount Bandai. The water is acidic with a pH value of approximately 5.0, and has a high degree of transparency. The water level was considerably less during the Jōmon period as numerous artifacts and ceramic fragments have been found offshore.
The lake water is an important source for irrigation in the Aizu region of western Fukushima Prefecture. An irrigation canal was completed during the Edo period and another, the Asaka Canal, in 1882. A third canal completed in 1915 supplies the city of Kōriyama with drinking and industrial water. The water also supplies a number of hydroelectric power plants. The lake is also an important tourist and leisure attraction in Fukushima Prefecture.