 The central and the eastern parts of the district belong to the basin of the Mologa, a tributary of the Rybinsk Reservoir in the basin of the Volga which drains into Caspian Sea.Udomelsky District is a part of the lake district located in the Valdai Hills, with the largest lakes within the district being Lake Udomlya, Lake Pesvo, and Lake Navolok, all in the drainage basin of the Msta.Most of the district area is covered by forest.