Lake Utonai

About Lake Utonai

A shallow freshwater lake, averaging about 0.6 m deep, on the lower Bibi River east of Tomakomai City. It was once an inlet of the sea, cut off about 3,000 years ago as sandspits and dunes formed at its mouth. It is one of Japan's major wintering and stopover sites for migratory birds: tens of thousands of geese, mainly greater white-fronted geese, arrive in spring, and more than 270 bird species have been recorded. It was designated a Ramsar Site in 1991. The area was once a vast wetland called the Yufutsu Plain; only this lake, its surrounding marshes and the Bibi River basin keep its former character.

Sources: Ministry of the Environment, Ramsar Site leaflet: Utonai-ko, Environment Agency of Japan, Lake Survey Report (1993) (sources in Japanese)

Lake data

Area

2.1 km²#26 in Hokkaido

Maximum depth

1 m#91 in Hokkaido

Average depth

0.6 m

Surface elevation

2.09 m

Transparency

0.8 m#51 in Hokkaidoas of the 1991 survey

Origin

Lagoon-origin lake

Lake type

Mesotrophic

Fresh or brackish

Freshwater

Freezing

Freezes in winter

Unmodified lake

No

Natural park

None

Ramsar Convention

Ramsar Site

Lake number

1030number in the national lake survey

Sources: Geospatial Information Authority of Japan, Area Statistics of Prefectures and Municipalities 2026 (as of July 1), Geospatial Information Authority of Japan, Lake Survey (surveyed 1999), Environment Agency of Japan, 4th National Survey on the Natural Environment: Lake Survey Report (1993). Area and depth use newer figures from the Geospatial Information Authority of Japan where available. Origin, lake type, transparency, freezing and unmodified status are as of the 1991 survey.

Themes that include Lake Utonai

• Lagoon-origin lakes
• Mesotrophic lakes
• Freshwater lakes