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Coco
Coco (Río Coco, Wangki/Wangli, Segovia): longest river of the Central American isthmus, 685 km, forming the Nicaragua–Honduras border, draining 28,280 km² into the Caribbean at Cape Gracias a Dios; home to Miskito communities.
Cocos Ridge
Cocos Ridge: ~1,000 km long aseismic submarine ridge on the Cocos plate, a Galápagos hotspot trace with ~20 km thick crust, now subducting flatly beneath Costa Rica at the Middle American Trench, driving uplift, subduction erosion, and earthquakes.
Cocytus (Κωκυτός)
Cocytus (Κωκυτός, Kokytos), the river of wailing of the Greek underworld, a branch of the Styx flowing into the Acheron in Homer; also a real Thesprotian tributary of the Acheron and Dante's frozen lake of Hell.
Colac Bay
Colac Bay (Ōraka) is a small Southland, New Zealand coastal township 12 km west of Riverton on SH99, facing Foveaux Strait; former 1900 timber-railway town of 2,000, now a holiday and surfing resort with NZ's only surfer statue and Takutai o te Tītī marae.
Cold-water geyser
Cold-water geyser (soda pop geyser, CO2-driven geyser): a spring erupting cold water below 20 °C via exsolving carbon dioxide, not steam. Type example Crystal Geyser, Utah, created by a 1936 oil well; studied as analogs of CO2 sequestration leakage.
Colorado (river, United States)
The Colorado River is a major river of the western United States and northwestern Mexico whose basin supplies water to about 40 million people and irrigates 5.5 million acres of farmland.
Colorado River
Colorado River: 1,450-mile Southwest lifeline through seven U.S. states and 30 Tribal Nations to the Gulf of California; governed by the 1922 Compact and Law of the River, now in a 26-year drought with Lake Mead and Lake Powell at record lows and post-2026 operating guidelines set in 2026.
Colorado River (Texas)
Colorado River (Texas): largest river wholly within Texas, rising in Dawson County and flowing 600 miles to Matagorda Bay; managed by LCRA through the Highland Lakes, supplying Austin and Coastal Plain rice farms.
Columbia Glaciated
Columbia Glaciated (FEOW ecoregion 120) is a freshwater ecoregion covering the glaciated upper third of the Columbia River basin in British Columbia, Washington, Idaho, and Montana; temperate upland rivers, no endemic fish, snowmelt-dominated flows.
Columbia River
The Columbia River is the largest river of the Pacific Northwest, rising in Columbia Lake, British Columbia, and flowing about 1,942 km to the Pacific near Astoria, Oregon. Known for its ~260,000 sq mi basin, major dams (Bonneville, Grand Coulee), salmon fisheries, tribal treaty rights, and the 1964 Columbia River Treaty with Canada.
Columbia River drainage basin
The Columbia River drainage basin is the 669,000-square-kilometer watershed of the Columbia River across seven U.S. states and British Columbia, defined by snowmelt-driven runoff, 29 major federal dams, the 1964 Columbia River Treaty, and declining salmon runs.
Columbia Unglaciated
Columbia Unglaciated, FEOW freshwater ecoregion 121, is the never-glaciated lower two-thirds of the Columbia River basin in Oregon, Idaho, Washington, Nevada, and Montana, a Pleistocene refugium with endemic Oregon chub.
Columbian exchange
The Columbian exchange is the post-1492 transfer of crops, animals, diseases, and people between the Americas and Afro-Eurasia, a term coined by Alfred Crosby in 1972.
Colville (lake)
Colville Lake (K'áhbamítué, "ptarmigan net place") is a lake in the Mackenzie region, Northwest Territories, Canada, at 67°10′N 126°0′W, named by John Franklin for Andrew Colville; the small Sahtu community of Colville Lake sits on its shore.
Colville (river)
Colville River (Kuukpik), largest river of Alaska's North Slope, flowing from the Brooks Range to a Beaufort Sea delta near Nuiqsut; ~60,000 km2 watershed, 290 m3/s mean discharge, Colville River Special Area.
Colville Ridge
Colville Ridge is an underwater volcanic ridge in the southwestern Pacific between New Zealand and Fiji, forming the southernmost 1,300 km of the Lau-Colville Ridge, a remnant volcanic arc west of the Kermadec Arc.
Committee Bay
Committee Bay is a bay in Nunavut, Canada, at 68°16′N, 86°54′W, whose shores host the Committee Bay Greenstone Belt, a roughly 300 km long gold exploration corridor.
Comoros - Mayotte
Comoros - Mayotte is a freshwater ecoregion covering the volcanic Comoros Islands in the Mozambique Channel, spanning about 2,171 km² across Grande Comore, Mohéli, Anjouan, and French Mayotte.
Complejo Cenagoso de Zapatosa
Complejo Cenagoso de Zapatosa: Colombia's largest continental freshwater wetland, about 1,900 interconnected ciénagas in Cesar and Magdalena departments; Ramsar site (2018) and DRMI (2019), connecting the Magdalena and Cesar rivers.
Complejo de Humedales Cuyabeno Lagartococha Yasuní
Complejo de Humedales Cuyabeno Lagartococha Yasuní, Ramsar site no. 2332, Ecuador's largest Ramsar wetland (773,668 ha), designated 24 August 2017, connecting Cuyabeno Wildlife Reserve and Yasuní National Park in the Amazonian Sucumbíos and Orellana provinces.
Complejo de Humedales de la Estrella Fluvial Inírida (EFI)
Estrella Fluvial Inírida (EFI), Colombia's 6th Ramsar site (No. 2217), a 250,158-ha wetland complex in Guainía where the Inírida, Guaviare, Atabapo, and Ventuari rivers form the Orinoco headwaters; designated by Decreto 1275 of 8 July 2014.
Complejo de Humedales de Matusagaratí
Complejo de Humedales de Matusagaratí, Ramsar site 2566 in Darién, Panama: 64,750-hectare wetland designated 28 June 2024, Panama's sixth Ramsar site, its largest wetland, with 259 bird and 51 fish species.
Complejo Lagunar Bahía Guásimas - Estero Lobos
Complejo Lagunar Bahía Guásimas-Estero Lobos (Ramsar site 1790) is a 135,198-hectare coastal wetland complex in Sonora, Mexico, designated 2 February 2008, with mangroves, major wintering waterbird and brant populations, and Yaqui territory.
Confluence
River confluence: the junction where two or more rivers merge into one channel, also called a river junction. Key features include the confluence hydrodynamic zone, scour holes, mouth-bars, controls such as discharge ratio and junction angle, and confluence mobility.
Congo River
The Congo River, also known as the Zaire River, is the second largest river in the world by drainage area and discharge, behind only the Amazon.
Coniferous swamp
Coniferous swamp: a forested wetland with at least 50 percent conifer canopy (white cedar, tamarack, balsam fir) where sphagnum moss is not the dominant substrate; saturated soils, hummocky surface, northern lake-basin settings, distinct from bogs and hardwood swamps.
Connecticut River
The Connecticut River is New England's longest river, over 410 miles from the Connecticut Lakes in New Hampshire through Vermont, Massachusetts, and Connecticut to Long Island Sound, with a 29,166 km² watershed.
Conservation and restoration of waterlogged wood
Conservation and restoration of waterlogged wood treats archaeological or historical wood from shipwrecks, wells, and bogs, most often by impregnation with polyethylene glycol followed by controlled drying.
Constructed wetland
Constructed wetland (artificial wetland, treatment wetland): an engineered wastewater treatment system using wetland plants, soils, and microbes. Shallow FWS or subsurface-flow beds remove BOD, nutrients, and metals at low energy and cost versus activated sludge.
Constructed wetlands for wastewater treatment
Constructed wetlands for wastewater treatment are engineered wetland systems that treat wastewater, with subsurface flow beds for secondary treatment and free-water surface wetlands for tertiary treatment.