The is a river on the island of Honshu in Shimane Prefecture and Tottori Prefecture, Japan. With a length of 153 km and catchment of 2540 km2, it is the largest river in the east of Shimane Prefecture. It flows through the cities of Izumo and Matsue and through the lakes Shinji and Nakaumi and discharges into the Sea of Japan. In the antiquity the river was known as "Izumo-no-okawa" (出雲大川, "The great Izumo river"). The River Hii significantly changed its course and transformed the land several times during last 7 millennia. Alluvial deposits carried by the river joined the Shimane peninsula to the mainland, which may have been represented in the "Kunibiki-shinwa" myth. Since the 17th century it flows into lake Shinji, and since the early 20th century continues to the Sea of Japan. Hii river frequently caused floods in its catchment. On the other hand, it was and currently is an important source of drinking and irrigation water. During the Edo period the upper Hii catchment was the largest iron-producing region in Japan. Nowadays the river is dammed for the production of hydropower. The largest dams are Obara and Hinobori. Geography The river's source is located on the slopes of Mount Sentsū, in the town of Okuizumo. The river flows northwards through the Chūgoku Mountains and Yokota Basin (横田盆地). Below Kisuki it joins Mitoya river (三刀屋川). In Izumo city it enters the , where it is connected to by the Hiikawa River discharge channel. Then it turns eastwards and flows through Lake Shinji and then through lake Nakaumi, discharging through the Sakai channel into Miho-wan bay of Sea of Japan. The part of the river that connects two lakes and crosses Matsue city is called (大橋川). The Hii river is 153 km long and the catchment area is 2540 km2; the population of the catchment is about 500.000. It is 19th longest river in Japan, and 29th largest by its catchment area. It is designated as a Class A river system by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT). The bottom gradient is about 1/160-1/700 in the upper reaches and 1/860-1/1500 in the lower part. The mean annual precipitation is about 2300 mm in the upper reaches and 1700–1845 mm in the lower reaches, most of it occurring in the southwestern part of the basin. The annual discharge in the midstream (Otsu, Izumo city) is 1.4