a river in Irkutsk Oblast, RSFSR. Length, 486 km; basin area, 18, 100 sq km. Arising on the northern slopes of the Vostochnyi Saian, it is a mountain river in its upper reaches. Fartherdown, its valley widens and its flow becomes calmer. Eventuallyit flows into Oka Gulf of the Bratsk Reservoir, which extends for320 km. The river is fed chiefly by rain. The average annual rateof flow at the city of Tulun, 119 km from the mouth, is 149 cum per sec. The river freezes over in late October or early Novem-ber and thaws in late April or early May. Its chief tributariesinclude the Kirei, from the right, and the Ikei and Ilir, from theleft.