Fishing and Paddling on the Reservoir

The lake supports a healthy population of five fish families spanning eleven species, including yamame (native char), amemasu (Dolly Varden), rainbow trout, brown trout, and the small wakasagi smelt. Rare species like the Ezo ugui (a local minnow) and flower sculpin also live here. Fishing is popular — you can buy a simple ¥200 day permit at the Shirakaba Campground on the lakeshore. Boat fishing is possible during the summer gate-open season (typically early June through late September), when a vehicle barrier allows trailer access.↗↗

Canoeing and rowing are the most consistently available water activities. Even during periods of low water level when the motorboat gate closes, canoes and small rowboats can still be launched. The broad, sheltered surface of the lake makes for peaceful paddling, with the birch-lined shores stretching away in every direction.↗↗

Camping Among the Birches

The Iwaonai Lake Shirakaba Campground (Birch Campground) sits directly on the lakeshore and is the area's base for multi-day visitors. Bungalows are available for those who prefer shelter over canvas, and the campground itself is surrounded by mature paper birch whose white trunks glow in the summer evening light. The setting earns strong reviews for its quiet, immersive natural atmosphere — a real contrast to the more crowded Hokkaido camping spots in the Daisetsuzan or Shiretoko areas.↗↗

Erica Park: A Hidden Seasonal Bloom

Adjacent to the lake is Erica Park, a surprising horticultural project where 60,000 plants of eleven varieties — including heather (Calluna) and their relatives — bloom in dense carpets of tiny one-centimetre flowers from roughly June through September. The genus Erica is native to southern Africa and Europe, so seeing it thrive in subarctic Hokkaido is a curiosity in itself. The park makes a pleasant short walk before or after time at the lake.↗↗

Getting There and When to Visit

Iwaonai Lake lies about 40 minutes by car from JR Shibetsu Station on the Sōya Main Line, roughly 1 hour 40 minutes from Asahikawa and about 3 hours 40 minutes from Sapporo via the Dō-Ō Expressway. There is no convenient public transport beyond the station, so a car is essential for a visit. The lake area is accessible year-round, but the gate for launching boats and watercraft typically opens from early June to September 30 between 9:00 AM and 3:30 PM. During low-water periods this gate may close temporarily, so checking the Shibetsu City website before a boat-focused trip is wise.↗↗↗

Summer (June–September) is the peak season for fishing, canoeing, and camping, while the surrounding birch and larch forest turns golden in late September and early October, making autumn colours another draw. Winter access is possible but facilities are closed and the landscape becomes a silent, frozen expanse — rewarding for visitors who appreciate solitude.

The Story Behind the Lake

Iwaonai Dam was built to tame the Teshio River, which at 256 km is the fourth-longest river in Japan and whose name derives from the Ainu word for "many beams" — a reference to the rock formations crossing its channel. Before the lake existed, this valley held a farming community of 173 households with its own schools, shops, and even a movie theatre. All were relocated when the reservoir filled in 1970–71. The dam's construction was a response to decades of catastrophic floods and severe droughts along the Teshio, and the lake it created now serves flood control, irrigation for over 14,000 hectares of farmland downstream, water supply for Shibetsu City, and hydroelectric power generation.↗↗