a river in Arkhangel’sk Oblast, RSFSR; a right tributary of the Vaga River of the Severnaia Dvina River basin. The Ust’ia measures 477 km in length and drains an area of 17,500 sq km. It is fed mainly by snow. High water lasts from April through June. The mean flow rate 107 km from the mouth is 92.4 cu m per sec. The river freezes over from late October to November, and the ice breaks up in the second half of April or the first half of May. The river is used for floating timber during high water. It is navigable in its lower course.