|- location||Confluence of the Kukenan- and the Yuruani Rivers|
|- elevation||2,650 m (8,690 ft)|
|Orinoco River in Ciudad Guayana|
|Length||952 km (592 mi)|
|Basin size||95,000 km2 (37,000 sq mi)|
|- average||4,850 m3/s (171,000 cu ft/s) at the mouth|
The Caroni River is the second most important river of Venezuela, the second in flow, and one of the longest, 952 kilometres (592 mi) from the Tepui Kukenan, where it originates with the same name Kukenan, up to its confluence with the River Orinoco to which it belongs. The name "Caroni" is applied starting from the confluence of the Kukenan with the Yuruani, at 182 kilometres (113 mi) from the source of the Kukenan and 770 kilometres (480 mi) from its discharge in the Orinoco. The meeting takes place in the south of Venezuela, in Bolivar State, being the most important tributary of the Orinoco, mostly because of the high discharge rate. The higher basin of the Caroni is situated in the Gran Sabana (Canaima National Park) close to the border with Brazil.
The Caroni is one of the rivers with the highest discharge rates in the world, with respect to the area of its basin. The average discharge is 4,850 cubic metres per second (171,000 cu ft/s), with variations caused by the wet/dry seasons. The average maximum discharge is 6,260 cubic metres per second (221,000 cu ft/s), and the average minimum is 3,570 cubic metres per second (126,000 cu ft/s). Among the historic extremes are 17,576 cubic metres per second (620,700 cu ft/s). The Caroni supplies 15.5 percent of the discharge of the Orinoco river. One of the characteristics of Caroni's water is the dark color, caused by the high amount of humic acids due to the incomplete decomposition of the phenol content of the vegetation. The Caroni therefore belongs to the blackwater rivers, as does the Negro River, or Rio Negro in Brazil, Venezuela and Colombia. In the late 1940s diamonds were found in the Caroni basin near the famous Lost World Region which then was accessible only by aircraft and four wheel drive vehicles.
The river drains the Guayanan Highlands moist forests ecoregion. The Caroni basin covers 95,000 square kilometres (37,000 sq mi) and is part of the Orinoco basin, the most important river of Venezuela. This means for the two big rivers that they have very similar hydrographic characteristics. The Caroni itself and its tributary the Paragua are rivers with a staircase, in the sense that many falls and rapids are alternated with stretches with gentle slopes, with many meanders and oxbow lakes (naturally cut off meanders). Among the most important falls of these rivers and their tributaries may be mentioned the Angel Falls, with the highest free fall of the world, almost 1,000 metres (3,300 ft), and the Kukenan Falls, the tenth on the world scale with a 610-metre (2,000 ft) free fall. Others are falls with less height but with a high volume of water, like the Aponwao Falls and the Caruay Falls, and rivers with these names: the Toron River, the Eutobarima River, the falls of the La Llovizna and the Cachamay River, these last three in the Caroni itself and the last just before its discharge into the Orinoco.
Because of its high discharge rate, with a yearly average of 4,850 cubic metres per second (171,000 cu ft/s) and a steep slope, the Caroni ideally suited for the generation of hydroelectric energy with four plants along its course (Macagua I, II and III), near its mouth, the Caruachi, some 30 kilometres (19 mi) aback, and lastly the plant of Guri, in the middle of Necoima or Necuima, some 80 kilometres (50 mi) from Puerto Ordaz. This plant has its reservoir, with an area of 4,000 square kilometres (1,500 sq mi), in the middle of the river, and has a power of 10,000 MW, and is now the third biggest in the world, after the Three Gorges dam in China (22,500 MW) and the Itaipu Dam in Paraguay and Brazil (14,000 MW)
The basin of the Caroni is one of the most spectacular and beautiful of the world, ideal for adventure tourism: a landscape of forests and savannah, innumerable waterfalls and cataracts, deep canyons and high plateaux, fast running streams with very clean water (darkly tinted, almost black when deep, blackwater river, beaches with pink sand, etc. Among the most notable of the basin of the Caroni, speaking for tourists, are the waterfalls of the Aponguao, of the Kama (Kama Meru in the Caribbean language) pemon, Eutobarima (in the Caroni itself, although not easily accessible), the lake and the plant of Guri, the parks of the waterfall and of the gorge of Kavak, the table mountains (tepuis) of the Roraima and the Kukenan.
Along the Caroní River between the confluence with the Icabarú River and San Salvador de Paúl, there are several artisanal gold mines, mainly on the left hand side of the river outside the national park, but a few can also be found on the right hand side inside the Canaima National Park. Besides the devastating effects of logging and deforestation to clear the site for the mines, the far greater danger is the use of mercury which poisons the Caroní river, its fauna and inhabitants living along its shore. High levels of mercury have been found not only in the Caroní river but also in Lake Guri and further downstream. The current government of Venezuela has pledged to reduce illegal mining activities with the sustainable development plan for mining 2016-2018. Illegal mining surged under the government of Hugo Chávez, due to the nationalization of mines run by international mining companies and this had the negative consequence of an increase of mercury use as other processes are more difficult and costly to use for illegal, artisanal mining. The fact that a river that is partly flowing through a national park is affected by this development is particularly troubling.
- "Treasure Hunt In A Lost World." Popular Mechanics, September 1950, pp. 73–79.
- Sears, Robin, South America: Southern Venezuela, northern Brazil, western Guyana, and eastern Colombia (NT0124), WWF: World Wildlife Fund, retrieved 2017-04-01