Isawa River

Isawa River
The Isawa River from Prefectural Road 235 in Kanegasaki
The Isawa River and Ishibuchi Reservoir in Iwate Prefecture
Native name	胆沢川
Country	Japan
Basin features
Main source	Mt. Yakeishi, Iwate Prefecture 1,000 m (3,300 ft)
River mouth	Kitakami River, Ōshū, Iwate
Physical characteristics
Length	27.9 km (17.3 mi)

The Isawa River (胆沢川, Isawagawa^?) is a river in Iwate Prefecture, Japan. For about half its length it marks the border between Kanegasaki Town and Ōshū City. The river's origin is in the Ōu Mountains just west of Mt. Yakeishi (1548 meters). At its highest point it is called the Sugiyachi Stream (スギヤチ沢, Sugiyachizawa^?) and flows south until it crosses National Route 397. There it turns west and follows 397 until it is stopped by the Ishibuchi Dam.

In 2013 a new dam was scheduled to be completed a little downstream called the Isawa Dam. When this dam is completed the Ishibuchi Dam and reservoir will be completely flooded. Many local residents are opposed to the construction of such a large dam as the water is being impounded to provide drinking and irrigation water for use in other places. Another fear is that the great weight of the water will trigger an earthquake destroying the dam and causing a major flood. One worker on the new dam was killed by a rockslide in the 2008 Iwate–Miyagi Nairiku earthquake. The Isawa River continues its course to the east-northeast until it empties into the Kitakami River in Mizusawa Ward, Ōshū.

In 802, after many battles with the Emishi, Sakanoue no Tamuramaro established Fort Isawa on the south side of the Isawa River where it joins the Kitakami. The location was in the very heart of the Isawa band of Emishi's territory. The Japanese invaders generally built their forts to the south of east or west flowing streams that empty into the Kitakami. The ruins are still preserved and there is a museum nearby with relics from the site.