Sededema

(upper course, Sredniaia Sededema), a river in the Yakut ASSR, a left tributary of the Kolyma. The Sededema is 567 km long and drains an area of 18,500 sq km. It originates on the Alazeia Plateau and flows primarily over the Kolyma Lowland. The basin contains approximately 3,000 lakes with a total area of more than 700 sq km. The Sededema is fed by snow and rain. It freezes in October, and the ice breaks up in May. The river’s main tributaries are the Kyllakh, D’iaski, and Ulakhan-Iuriakh, from the left, and the Sykynakh, from the right.