Waters and hydrographic features

Athabasca (river)

Athabasca River, Alberta river over 1,200 km from Jasper National Park to Lake Athabasca; fur trade route, Athabasca Pass 1811, heritage river 1989, main water source for oil sands mining.

Athirappilly Falls (അതിരപ്പിള്ളി വെള്ളച്ചാട്ടം)

Athirappilly Falls (അതിരപ്പിള്ളി വെള്ളച്ചാട്ടം), the Niagara of India, is Kerala's largest waterfall: an 80-foot, 100-meter-wide cascade on the Chalakudy River in Thrissur district, famed for hornbills and a contested 163 MW dam project.

Athos / Ormos Vatopediou

Ormos Vatopediou (Vatopedi Bay) is the broad bay on the northeast coast of the Athos peninsula, Greece, named for Vatopedi Monastery and its harbour Arsanas Vatopedi; boat-only access, Diamonitirion permit, male pilgrims only.

Oct 15, 2026

Atlantic meridional mode

The Atlantic meridional mode (AMM) is the dominant mode of coupled ocean-atmosphere variability in the tropical Atlantic, an anomalous north-south sea surface temperature gradient across the equator.

Atlantic meridional overturning circulation

Atlantic meridional overturning circulation (AMOC): basin-scale Atlantic current system moving ~17 Sv northward and ~1.2 PW of heat, driven by Labrador and Nordic Seas deep-water formation; monitored by RAPID since 2004 and projected to weaken 18–43% by 2100.

Oct 15, 2026

Atlantic multidecadal oscillation

The Atlantic multidecadal oscillation (AMO), or Atlantic multidecadal variability (AMV), is a fluctuation of North Atlantic sea surface temperature on a 60–80 year time scale, linked to rainfall and hurricanes.

Oct 15, 2026

Atlantic Niño

The Atlantic Niño is an episodic warming of the eastern equatorial Atlantic Ocean, a smaller, shorter counterpart of Pacific El Niño that peaks in boreal summer and affects Sahel rainfall.

Atlantic Northwest Africa

Atlantic Northwest Africa is FEOW freshwater ecoregion 501, a Palearctic temperate coastal rivers unit along Morocco, Western Sahara, Mauritania, Algeria, and Spain, with Iberian faunal elements, Africa's only native salmonid, and high endemism.

Atlantic Ocean

The Atlantic Ocean is Earth's second largest ocean basin, about 106,460,000 km² (20% of Earth's surface), between the Americas and Europe-Africa, home of the AMOC and Gulf Stream.

Atlantic slave trade

Atlantic slave trade (transatlantic slave trade): forced transport of 10-12 million enslaved Africans to the Americas, 16th-19th centuries, via the triangular trade and Middle Passage; about 2 million died at sea; documented in the SlaveVoyages database.

Auob

Auob (Auobrivier), an ephemeral "fossil" river of the southern Kalahari rising in Namibia's Anas Mountains, joining the Nossob near Twee Rivieren; name means bitter water; its aquifer supplies the Stampriet system.

Australasian wetland flora

Australasian wetland flora is the collective vegetation of Australia's and New Zealand's swamps, marshes, bogs, billabongs, and floodplains, from water lilies to floodplain trees such as river red gum.

Australian state and territory wetland policy

Australian state and territory wetland policy is the set of state and territory laws and strategies protecting Australia's wetlands, since land and water management rests with the jurisdictions.

Auvert Bay

Auvert Bay is a bay between Cape Evensen and Cape Bellue on the Graham Coast, Antarctic Peninsula, at 66°14′S 65°45′W. Charted by the French Antarctic Expedition 1908–10 as Baie Auvert, approved by the UK APC in 1953.

Awash

Awash, river and basin in Ethiopia; also Awash River Basin. A roughly 1,200 km endorheic river ending in salt lakes in the Danakil Plain; Ethiopia's most intensively irrigated basin, home to Koka Dam, Wonji and Metehara sugar estates, severe water pollution, and major flood management works.

Ayakum

Ayakum (Ayakkum) Lake, a closed-basin saltwater lake in the Kumukuli Basin between Altyn Tagh and Kunlun mountains, northern Tibetan Plateau, Xinjiang, China; expanded from 623 km² (1990) to over 1140 km² (2023), becoming Xinjiang's largest lake.

Aydar

Aydar (Aydar Ko'li, Aydarkul) is a large brackish artificial lake in Uzbekistan's Kyzylkum Desert, formed in 1969 by 21.8 km3 of Chardarya reservoir flood discharge; part of the 4,000 km2 Ramsar-listed Aydar-Arnasay lake system with fisheries and ecotourism.

Azores

The Azores (Açores) are a Portuguese autonomous region of nine volcanic islands in the North Atlantic Macaronesia, straddling the North America-Eurasia-Nubia triple junction, with 241,025 residents and a large tourism and conservation economy.

Bab-el-Mandeb (باب المندب)

Bab-el-Mandeb (باب المندب, Gate of Tears) is the 18-mile-wide strait between Yemen and Djibouti connecting the Red Sea to the Gulf of Aden; a key oil chokepoint carrying about 6.2 million b/d in 2018, halved by Houthi attacks from November 2023.

Bacias hidrograficas

Bacias hidrograficas is the Portuguese term for drainage basins, or watersheds: land areas that drain water, sediment, and dissolved materials to a common stream outlet.

Badab-e Surt (باداب سورت)

Badab-e Surt (باداب سورت), also Badab Soort, is a stepped travertine terrace spring site at 1,841 m in Mazandaran, Iran, 95 km southeast of Sari, formed by two mineral springs, one salty and one iron-rich orange, registered as a national natural monument in 2008.

Baffin Bay

Baffin Bay, also called Baffin's Bay, is an Arctic marginal sea between Greenland and Baffin Island, about 1,130 km long and over 2,740 m deep, linking the Arctic Ocean to Davis Strait; ice-covered most of the year with rapid sea-ice decline.

Bafing

Bafing River, main headwater tributary of the Senegal River, rises in the Fouta Djallon, Guinea, and joins the Bakoye at Bafoulabé, Mali; it supplies about half the Senegal's flow and carries the Manantali Dam.

Bagnères-de-Luchon

Bagnères-de-Luchon (Luchon), Pyrenean spa town in Haute-Garonne, France, at 627 m near Spain; Roman-era thermal springs, revived by d'Étigny from 1759, Thermes Chambert 1857, Superbagnères ski resort, reopened 2025 rail line.

Bagni di Lucca

Bagni di Lucca is a town and spa center in Tuscany, Italy, known for thermal springs that made it one of Europe's most elegant 19th-century spas.

Bahama Basin

Bahama Basin: undersea basin of the North Atlantic at 29°15'N, 74°15'W, east of Bahama Ridge, named 1992 (SCUFN, proposer Troy L. Holcombe); part of the Blake-Bahama Basin deep beside the Bahama carbonate banks.

Bahía de Samborombón

Bahía de Samborombón (Samborombón Bay), a 243,965-ha Ramsar wetland on the Río de la Plata estuary, Buenos Aires, Argentina, designated 1997; refuge of the endangered Pampas deer and migratory shorebirds.

Bahía Grande

Bahía Grande ("Big Bay") names several places: a 272-km bay of the Argentine Sea in Santa Cruz Province, Patagonia; a restored tidal basin at the southern tip of Texas; bays in Chile and Oaxaca; a Lago Fagnano sub-basin; and an Argentine shipping company.

Bahiret el Bibane

Bahiret el Bibane (Bahiret el Biban), a hypersaline coastal lagoon of about 230 km2 in southeastern Tunisia near the Libyan border, a Ramsar site since 2007 famed for its 3.5 km traditional bordigue fish barrier and nursery fisheries.