Teshio River

The Teshio (Japanese: 天塩川, Teshio-gawa) is a river in northern Hokkaidō, Japan. Its length of 256 km makes it the fourth longest river in Japan and due to its few tributaries its 5590 km² basin is the tenth largest in Japan in area. Teshio's name originates from the Ainu language, in which it is called Tesh-o-pet (Tesh = river trap for fishing, pet = river).

The river originates from Mount Teshio in central Hokkaido, running north-northwest to the Nayoro Basin where it receives its inflow from the Nayoro River. The river continues through the valley meandering to the Teshio Plain facing the Sea of Japan. Before flowing into the sea, due to the presence of sand dunes, it changes its course to the south, flowing 10 km south of the Teshio town. The origin of the names of the different geographical features are related to the river.

The Iwaonai Reservoir (岩尾内ダム, iwaonai dam - dam in English) located in the upper part of the course supplies drinking water and electricity to the area and the lower part of the course is used as northern limit for rice cultivation in Japan. The population in the area is sparse, although the cities of Shibetsu and Nayoro are present.

The first shipping navigation in the lower course was that of a Nagato-maru vera ship in 1900. Steamships began their traffics in 1909. The terminal port was Shibetsu in 1901 and Nayoro in 1904. The ships began in April and ended in November avoiding ice. Today there is no transport ship transit.

Despite not being a famous river even among the Japanese, the river is popular among adventure sports enthusiasts because it allows kayaking trips of up to 100 miles without obstacles.