Lake Abashiri, located in the Okhotsk region, is a brackish water lake crowded with people who enjoy canoeing and yachting in summer. In winter, it is a tourist spot where people can enjoy ice fishing.
When the tide of the Sea of Okhotsk is high, sea water flows back into Lake Abashiri, causing high salinity water to stay on the bottom of the lake, forming an anoxic layer. This caused a water bloom in 1987, and a large amount of water algal in 1989, which led to a study on how to improve the water environment of Lake Abashiri, and people in the basin have been working together to promote countermeasures.
To prevent the saltwater boundary layer from rising due to the backflow of seawater, the Abashiri River Omagariseki has been operated only during the winter since January 2014.
It is a rare sight to see the gate rise up to hold back the seawater during the backflow.

◎Omagariseki: saltwater boundary layer control

Prior to the operation of the Omagariseki, a weekly survey is conducted to determine the location of the saltwater boundary layer in the icy Lake Abashiri, even in the harsh winter environment.

◎Lake Abashiri Water Quality Survey/span>