Overview
Ohnagami Dam is a gravity concrete dam built across the Sufu River near Tochigi in the Yasaka district of Hamada, Shimane Prefecture. Standing 71.5 meters high with a crest 334 meters long, it is an imposing barrier, and the reservoir it holds back bears the name Koyoko, the Lake of Autumn Leaves. Though it is a practical dam serving flood control and water supply, the interplay of its mountain-ringed water surface and the surrounding greenery makes it a pleasure to visit.
Highlights
- ●A gravity concrete dam 71.5 meters high with a crest 334 meters long
- ●A barrier built over a long span, begun in 1974 and completed in 2003
- ●The scenery of Koyoko, the reservoir formed by damming the Sufu River
- ●Its practical role in flood control and water supply
History
Construction of Ohnagami Dam began in 1974 and was completed in 2003, a gravity concrete dam raised over nearly three decades. Its sturdy structure resists the water's pressure through the sheer weight of its concrete. The catchment area reaches about 106.2 square kilometers, and the dam performs the roles of flood control and water supply for the Sufu River basin. After its long period of construction it became a support for local life and disaster prevention, a dam that speaks to the history of water management in the San'in region.
Access
The dam lies at roughly 34.83 degrees north and 132.11 degrees east, tucked into the hills at Tochigi in the Yasaka district of Hamada. Set in a mountainous area inland from central Hamada, it is essentially reached by car. Because the approach follows mountain roads, conditions, the areas open to visitors, and the availability of parking may change, so checking official information before you set out is reassuring. The surroundings form a nature-rich hill-and-valley district.
Best season
As the reservoir's name Koyoko, the Lake of Autumn Leaves, suggests, autumn is an especially fine time when the surrounding trees take on color. The foliage mirrored on the water is one of the real delights of a visit here. The fresh greenery of early summer and the clear face of the brimming lake are appealing too. Since this is mountain country, prepare for changing weather and plan a comfortable, unhurried trip.
Map
34.8275, 132.1092 · Wikidata
Suggested itinerary
- 1Drive from central Hamada into the hills at Tochigi in the Yasaka district toward Ohnagami Dam
- 2Take in the 71.5-meter crest of the gravity dam and sense the scale of the structure
- 3Enjoy the surrounding greenery and, in season, the autumn colors along the shore of the Koyoko reservoir
- 4On the way back, round off the day with the nature along the Sufu River and the sights of central Hamada
Did you know?
💡 The name Koyoko, meaning Lake of Autumn Leaves, given to the reservoir is thought to come from the beautiful coloring of the surrounding hills in autumn. Even for a working dam, the name kindles anticipation of the seasonal scenery.
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