The Byssa (Russian: Бысса) is a river in Selemdzhinsky District, Amur Oblast, Russia. It is the third longest tributary of the Selemdzha, with a length of 235 kilometres (146 mi)[1] and with 6,370 square kilometres (2,460 sq mi) the third in drainage basin area, after the Orlovka. The name of the river originated in the Evenki language.[2]
The river flows across a largely uninhabited area except for Byssa and Fevralsk villages in the area of its mouth. South of Fevralsk the river is crossed by the Far Eastern Railway line.[3]
The Byssa is a left tributary of the Selemdzha. It has its origin at an elevation of about 800 m (2,600 ft) in the northwestern slopes of the Turan Range. The river flows in a roughly southwestern direction with rapids and a winding channel in its upper reaches. After leaving the mountainous area it enters a wide swampy valley where it meanders slowly all along its middle and lower course.[1][4] Finally it meets the left bank of the Selemdzha 206 kilometres (128 mi) from its mouth in the Zeya.[1]
The main tributaries of the Byssa are the 73 kilometres (45 mi) long Iga from the left and the Sinnikan from the right.[4] There are hot springs in the middle basin of the river where the water reaches a temperature of 43 °C (109 °F).[5]
