a river in Khabarovsk Krai, RSFSR. The Tumnin is 364 km long and drains an area of 22,400 sq km. It rises in the Sikhote-Alin’ mountains, through which it flows before emptying into the Tatar Strait. The river is fed by mixed sources, but predominantly by rain. During the summer there are three to four freshets, which cause a high water. The mean flow rate is 252 cu m per sec. The Tumnin freezes in November, and the ice breaks up in late April or early May; the river is navigable in the lower course. Its waters are used as a water-supply source for residential and industrial consumers. The Komsomol’sk-na-Amure-Sovetskaia Gavan’ railroad line runs through the valley of the Tumnin’s lower course.