The Plateau of Tibet is a prime source of water for Central Asia. The Indus River, known in Tibet as the Shih-ch'üan Ho (in Tibetan, Sênggê Zangbo: "Out of the Lion's Mouth"), has its source in western Tibet near Mount Kailas, a mountain sacred to Buddhists and Hindus; it then flows westward across Kashmir to Pakistan. Three other rivers also begin in the west. The Hsiang-ch'üan River (Tibetan Langqên Kanbab: "Out of the Elephant's Mouth") flows west to become the Sutlej River in western India; the K'ung-ch'üeh River flows into the Kauriala to eventually join the Ganges River; and the Ma-ch'üan River (Tibetan Damqog Kanbab: "Out of the Horse's Mouth") flows east and, after joining the Lhasa (La-sa) River south of Lhasa, forms the Brahmaputra River. 

The Salween (Nu) River has its source in east-central Tibet, from where it flows through eastern Tibet and Yunnan and then enters Myanmar. The Mekong River begins in southern Tsinghai as two rivers--the Ang and Cha--which join near the Tibet border; the river then flows through eastern Tibet and western Yunnan and enters Laos and Thailand. The source of the Yangtze River rises in southern Tsinghai, near the Tibet border; after flowing through southern Tsinghai, the Yangtze turns south to form most of the Tibet-Szechwan border. 

Among the province's lakes, the three largest are located in central Tibet, northwest of Lhasa: Lakes T'ang-ku-la-yu-mu (Tibetan Tangra Yum), Na-mu (Nam), and Ch'i-lin (Ziling). South of Lhasa lie two large lakes, Yang-cho-yung (Yamdrok) and P'u-mo (Pomo). In western Tibet two adjoining lakes are located near the Nepal border, Ma-fa-mu Lake, sacred to both Buddhists and Hindus, and Lake La-ang (Langak).

Soils are alluvial and are often composed of sand that is blown by the wind to form a layer above gravels and shingles. Colour varies from light brown to gray, according to the humus content, which is generally poor.