[1][5] The mainstream originates from Mount Asa (阿佐山) located in Kitahiroshima, Hiroshima (former Geihoku).

The gradients being relatively gentle, the river had been commonly used for boat transport until 1930s, when Sankō Line and trafficways were built and opened.

[1][6][7][8] It is known for ukai (鵜飼い) or cormorant fishing for ayu, which can be found especially in Miyoshi.

According to one theory ukai in Miyoshi has taken place since late Sengoku Period, and is now one of the tourist attractions of the city.

As of 2000 according to the national census 278,207 people lived in the drainage basin, including 104,169 from Shimane and 174,038 from Hiroshima.