a river in Chita Oblast, RSFSR; a left tributary of the Shilka (Amur River basin). It measures 580 km long and drains an area of 27,500 sq km. The Nercha rises on the slopes of Mount Chernyshev (of the Olekma Stanovik system of ranges) and flows in a broad valley. It is fed primarily by rain. There is high water from May through October. The mean flow rate is 90 cu m per sec. The Nercha begins to freeze in October, and its lower course is frozen completely from January until April; the ice breaks up in late April or early May. The river is used for floating timber. The city of Nerchinsk is located on the Nercha. Gold is mined in the Nercha River basin.