Lake Hachiro is located in the west central part of Akita Prefecture and is a freshwater lake remaining by the reclamation of Hachiro Lagoon. It has an area of 47.3 km2, a total capacity of 132,600,000 m3, and catchment area is 894.3 km2 consisting of “regulating reservoirs”, “eastern area”, and “western area”.
In the past, before land reclamation, Hachiro Lagoon was once the second largest Lake in Japan, measuring 12 km east and west and 27 km north and south, with an area of 220.2 km2, and a vast brackish lake.
On the other hand, many reclamation plans were conceived for the purpose of developing agricultural land, for the reason the depth of the water was shallow, only 4 to 5 m at its deepest point. Then, the government initiated a national land reclamation project to solve the postwar food shortage in 1957, and the present Lake Hachiro was born in 1977.
Lake Hachiro flows from by more than 20 small and medium-sized rivers flowing into the lake from its eastern basin. The lake's water was desalinated by cutting off the Japan Sea at the tide gate installed in the Funakoshi Channel during the reclamation project. Today, the water is used for agricultural purposes by Oogata Village and other basin cities, where paddy rice and other crops are grown. In addition, the lake has a thriving fishing industry, with Wakasagi (Japanese pond smelt) and Shirauo (whitebait) as the main species of fish, providing many blessings to the people.
However, the lake gradually became eutrophic after the completion of the reclamation project. As a result, water pollution problems, such as the abnormal occurrence of blue-green algae, became more pronounced. Akita Prefecture established the Hachiroko Environment Policy Office in 2006 and has been promoting various water quality preservation measures.