Sarugaishi River

Late afternoon fishermen on the Sarugaishi in Miyamori.

The ISarugaishi River (猿が石川, Sarugaishigawa) is a river in Iwate Prefecture, Japan.

The Sarugaishi River rises in the Kitakami Mountains just south of Mt. Yakushi in Tōno and empties into the Kitakami River in Hanamaki. The Tase Dam is situated on the Sarugaishi River, in eastern Hanamaki in the former town of Towa. This dam was completed in 1953. There is a legend that the entire floodplain of the river in Tōno was once a large lake dammed by the hills in Miyamori. Looking out over the plains of Tōno from a high elevation in Spring, after the rice paddies are flooded, it is easy to imagine what it might have looked like.

Course

From its headwaters in Hayachine Quasi-national Park near Mt. Yakushi The Sarugaishi flows directly south through the Tsukimoushi section of Tōno City. In Matsuzaki the river makes a slow and gentle bend to the west and flows west-southwest through Ayaori. In Miyamori the Sarugaishi encounters large hills that force the river into a steep and winding canyon which continues into Hanamaki where the Tase Dam impounds the water.

Lake Tase bends back to the north with the outflow of the dam directed eastward. The river then bends back around to flow west-northwest to Towa then winds in a series of loops generally westward before turning directly north and entering the Kitakami River opposite the mouth of the Segawa and just to the north of the Igirisu Coast of the Kitakami.

Tributaries

The Dokugawa and the Tozenjigawa join the Sarugaishi in Tsukimoushi.

The Kogarasegawa is a large tributary that forms near Tachimaru Toge Pass and joins the Sarugaishi in Matsuzaki. National Route 340 follows along this scenic river for most of its length.

The Hayase begins in the region of Sennin Toge Pass and empties into the Sarugaishi in downtown Tōno as the largest tributary. National Route 283 parallels the course of this river and provides spectacular views, especially in the higher elevations.

The Rainai forms just north of Warabi Toge Pass and empties into the Sarugaishi River near the mouth of the Hayase. The Rainai is dammed in two places for Tono's drinking water supply.

The Yamaya forms in the area of Ko Toge Pass. National Route 396 follows the course of the river for about half of its length.

The Miyamori enters just north of Tase Dam.