Teshio River

The Teshio River (天塩川, Teshio-gawa) is a river in Hokkaidō, Japan. At 256 kilometres (159 mi), it is the second-longest river on the island (after the Ishikari) and the fourth-longest in the country (after the Shinano, Tone, and Ishikari).[2] A Class A river, the Teshio is the northernmost major river in Japan, and has been designated Hokkaidō Heritage.[2][3][4] Matsuura Takeshirō is said to have come up with the name “Hokkaidō” during his exploration of the river’s interior.[5]

The name of the river derives from the Ainu tesh・o・pet (テシ・オ・ペッ), meaning “river full of fishing weirs”, perhaps because of rocks dotted across the river in such a shape.[1][6] Alternatively, there is a locale in Bifuka that has been designated a municipal Historic Site as the “Place of Derivation of the Teshio River” (天塩川由来の地) on the basis that it was while staying here, during his exploration to the source of the river, on the seventh day of the sixth month of Ansei 4 (1857), there being a fishing weir at the spot, that Matsuura Takeshirō (松浦武四郎) recorded the river’s name.[7] Due to works on the river in recent years the rocks in its middle course that perhaps inspired the name themselves largely no longer exist.[1]

The river’s source is at Mount Teshio (1,558 metres (5,112 ft)), highest of the Kitami Mountains.[1] Flowing down through the mountain valleys from its origins in Shibetsu, it is fed by tributaries (of which it has some 160[2]) including the Nayoro River (名寄川), then crosses the mountain plains, passing next through the more-constricted topography of Otoineppu before entering the Teshio Plain, where it meanders until flowing into the Sea of Japan at Teshio.[1] The lower 158 kilometres (98 mi) are, unusually, unbroken by dams and weirs and can be navigated uninterrupted.[1][5]