710 articles
Upper Lancang (Mekong)
Upper Lancang (Mekong), ecoregion 724, the Chinese upper Mekong basin (Lancang Jiang, turbulent river). Tibetan Plateau headwaters, 11-dam cascade impounding 45.6 km3, 86.5% sediment trapping, endemic Schizothoracinae and Glyptosterninae fishes.
Upper Mackenzie
Upper Mackenzie (FEOW ecoregion 104) is a Canadian freshwater ecoregion of temperate floodplain rivers and wetlands covering the upper Mackenzie watershed across Alberta, British Columbia, Saskatchewan, and the NWT, defined by the Peace, Slave, Athabasca, and Hay rivers and the Peace-Athabasca Delta.
Upper Mississippi
Upper Mississippi: river reach from Lake Itasca, Minnesota, to the Ohio River confluence at Cairo, Illinois; with the Illinois River it forms the 1,300-mile UMRS, a 1986-designated national ecosystem and 9-foot-channel navigation system.
Upper Missouri
The Upper Missouri refers to the upper portion of the Missouri River and its basin, spanning Montana, Wyoming, the Dakotas, and Nebraska down to the Missouri–Platte confluence near Omaha.
Upper Parana
Upper Parana, or Upper Paraná, is a freshwater ecoregion covering the Rio Paraná basin above the former Guaíra Falls, mostly in Brazil and known for 131 endemic fish species.
Upper Salween
Upper Salween: FEOW freshwater ecoregion 721, Palearctic, tropical and subtropical upland rivers, covering the Salween (Nu) basin in China north of the Nanding River confluence, with 8 endemic fish species.
Upper Saskatchewan
Upper Saskatchewan (FEOW ecoregion 107) is a temperate upland rivers ecoregion covering the Saskatchewan River headwaters from the Canadian Rockies across southern Alberta and western Saskatchewan, with 41 fish species and endangered conservation status.
Upper Snake
Upper Snake: the Snake River above Shoshone Falls, Idaho, and its drainage (FEOW ecoregion 122), spanning Idaho, Wyoming, Nevada, and Utah; defined by the falls as a fish barrier, endemic sculpins, Reclamation reservoirs, and 487 kaf salmon flow augmentation.
Upper Tigris & Euphrates
Upper Tigris & Euphrates (FEOW ecoregion 442), a Palearctic temperate floodplain freshwater ecoregion in Turkey, Iraq, Syria, and Iran covering the upper Tigris and Euphrates rivers, their tributaries, and Iranian drainages, with high fish endemism and severe upstream-dam water stress.
Upper Uruguay
Upper Uruguay, FEOW freshwater ecoregion 333 (Alto Uruguay), the Río Uruguay basin above Yucumã Falls in Brazil and Argentina; basalt upland rivers with 27 endemic fish species and heavy dam impoundment.
Upper Usumacinta
Upper Usumacinta, FEOW freshwater ecoregion 174, tropical and subtropical upland rivers in eastern Chiapas, southeastern Tabasco, and northwestern Guatemala; upper Usumacinta basin above the San Pedro confluence, home of the endemic Chiapas catfish.
Upper Yukon
Upper Yukon (FEOW ecoregion 102) is a Nearctic Polar freshwaters ecoregion covering the upper Yukon River watershed in Yukon, British Columbia, and Alaska, draining to the Bering Sea, with a depauperate fish fauna and no endemic species.
Ural
Ural (Урал; Kazakh Zhayyq; formerly Yaik until 1775), third longest river in Europe at 2,428 km, rising in the southern Ural Mountains and flowing through Russia and Kazakhstan to the Caspian Sea; only free-flowing Caspian tributary, with the basin's last natural sturgeon spawning grounds.
Uša (river, Lithuania)
Uša (Ušà) is a 105-km Belarusian river, a left tributary of the Nemunas rising southwest of Nesvizh, with a 1,220 km² basin, 7.3 m³/s mean discharge, frozen December to March; distinct from the same-named Neris tributary.
Usa (river, Russia)
Usa (Уса), river in the Komi Republic, Russia; largest tributary of the Pechora, 565 km long, basin 93,600 km², mean discharge 1,310 m³/s, frozen November to May, navigable 325 km from Ust-Usa.
Usumacinta
The Usumacinta is a Mesoamerican river about 1,100 km long, formed in Guatemala and flowing north through Chiapas and Tabasco to the Gulf of Mexico.
Utus
Utus is the ancient Latin name of the Vit River in northern Bulgaria, a Danube tributary in Roman Moesia that marked a position on the Danube frontier.
Vaal
Vaal (Lekoa): main tributary of South Africa's Orange River, about 1,300 km long, draining the central highveld; supplies Gauteng via the Vaal Dam, Barrage, and Lesotho Highlands transfers.
Vakh
Vakh (Вах) is a 964 km river in Khanty-Mansia, western Siberia, a right tributary of the Ob with a 76,700 km² basin, mean discharge 665 m³/s, navigable 453 km, and the Samotlor oil field in its basin.
Vardar
Vardar (Вардар; Greek Axios, Αξιός), major Balkan river, 388 km, rising near Vrutok, North Macedonia, flowing to the Aegean Thermaikos Gulf; second largest Balkan catchment after the Evros.
Vasyugan
The Vasyugan (Васюган) is a 1,082 km river in Tomsk Oblast, Russia, and a left tributary of the Ob, rising in the Vasyugan bogs of the West Siberian Plain.
Vegas - Virgin
Vegas - Virgin, FEOW freshwater ecoregion 129, a desert ecoregion of southeastern Nevada, northwestern Arizona, and southwestern Utah covering the Virgin, White, and Moapa river basins, with endemic spinedaces, springfish, and the Virgin chub.
Verkhniy Yenisey
Verkhniy Yenisey (Ulug-Khem, Upper Yenisey) is the upper course of the Yenisei River in Tuva, Russia, from the Maly and Bolshoy Yenisey confluence at Kyzyl; 188 km to the Khemchik mouth, 1,238 km to the Tuba under the wider definition.
Vetluga
Vetluga (Ветлуга, Mari: Ener): an 889 km left tributary of the Volga flowing through Kirov, Kostroma, Nizhny Novgorod oblasts and Mari El, and a 1778-chartered district town of 9,400 people (2005) on its right bank.
Vilyuy
Vilyuy (Вилюй) is a 2,650 km Siberian river, the largest left tributary of the Lena in Yakutia, with a 454,000 km² permafrost basin, a dam at Chernyshevsky, and diamond-mining region around Mirny; distinct from a small Neyva tributary of the same name.
Vindelälven
Vindelälven (Vindel River), a 450 km unregulated national river in northern Sweden, free of hydropower dams, a Ramsar site (no. 2181, 66,395 ha, 2013), and core of the UNESCO Vindelälven-Juhttátahkka biosphere reserve (2019).
Vĩnh Tế Canal
The Vĩnh Tế Canal (Kênh Vĩnh Tế) is an 87 km canal in Vietnam's Mekong Delta, dug under the Nguyễn dynasty between 1819 and 1824.
Virgin River
Virgin River: about 163-mile Colorado River tributary rising above Zion National Park, Utah, flowing through Arizona and Nevada into Lake Mead; home to endangered woundfin and Virgin River chub.
Vistula
The Vistula (Wisła) is Poland's longest river, 1,022 km from Barania Góra to the Baltic, with a 194,000 km² basin covering 54% of Poland. Historic grain-trade artery to Gdańsk, engineered by the Przekop cross-cut and the 2022 Vistula Spit ditch, now hit by salinity, sand extraction, and 2025 record-low levels.
Vitim
Vitim (Витим) is a 1,837 km right tributary of the Lena in eastern Siberia, draining 225,000 km², with rain-fed flow, Bodaybo gold mining, and Pleistocene glacial Lake Vitim megafloods.