Isawa River

Isawa River (胆沢川 Isawagawa) is a river in Iwate Prefecture, Japan. For about half its length it marks the border between Kanegasaki Yown and Ōshū City. The river's origin is in the Ōu Mountains just west of Mt. Yakeishi (1548 meters). At it's highest point it is called the Sugiyachi-zawa (スギヤチ沢) 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 is 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 Mt. Kurikoma earthquake.

The Isawa River continues its course to the east-northeast until it empties into the Kitakami River in Mizusawa Ward, Ōshū City. In 802 Sakanoue no Tamuramaro established Fort Isawa on the south side of the Isawa River where it joins the Kitakami. The Japanese invaders generally built thier forts to the south of east or west flowing streams that empty into the Kitakami. The opposing Emishi fort on the north side of the Isawa is the Tonomi Palisade which was partly obliterated by the construction of the Tōhoku Expressway.