River bifurcation

Bifurcation in Hövelhof, Germany

River deltas such as the pictured delta of the Salween River in Myanmar often show bifurcations. The water flows in from the lower section of the image and passes on both sides of the large island in the center.

River bifurcation (from Latin: furca, fork) occurs when a river flowing in a single stream separates into two or more separate streams (called distributaries) which continue downstream. Some rivers form complex networks of distributaries, especially in their deltas. If the streams eventually merge again or empty into the same body of water, then the bifurcation forms an island.

River bifurcation may be temporary or semi-permanent, depending on the strength of the material which separates the distributaries. For example, a mid-stream island of soil or silt in a delta is most likely temporary. A location where a river divides around a rock fin, e.g. a volcanically formed Dike, or a mountain, may be more lasting. A bifurcation may also be man-made, for example when two streams are separated by a long bridge pier.

Examples

One example of a navigable natural bifurcation is the Casiquiare canal that links the Orinoco River with the Amazon.

Another occurrence of a river bifurcation was in Serbia^{[1][2][3][4][5]}, Europe in the Nerodimka River. The Nerodime Bifurcation was a hydrological curiosity: separate streams flowed into the Aegean and the Black Seas. The Bifurcation was located in the southern part of the Kosovo territory of Uroševac Municipality. The Bifurcation of Nerodimka was the first hydrological protected object in Serbia (1979). The Nerodimka Bifurcation is a strict wildlife sanctuary, category I according to (IUCN)^{[clarification needed]}, with an area of 13.0 ha (about 32 acres). This bifurcation is considered to be an artificial phenomenon, but created under extremely favorable natural conditions.

In the past, the small Kalaus River in south-western Russia, when reaching the thalweg of the Kuma-Manych Depression at 45°43′N 44°06′E / 45.717°N 44.1°E / 45.717; 44.1, would split, the two distributaries becoming the headwaters of the West and East Manych Rivers. The former flows west into the Don River and eventually into the Sea of Azov, while the latter flows east, and is lost in the steppe before ever reaching the Caspian Sea. However a dam was built, preventing water from flowing from the Kalaus into the East Manych; thus the Kalaus is now the source of the West Manych only.^[6]

The Bahr Yussef is a channel which splits off the west side of the Nile and drains into the Birket Qarun, an inland sea in the Fayum Depression. Originally a natural bifurcation for flood waters, its flow was increased by canalisation in the 12th Dynasty (about 1900 BC). Around 230BC, the channel of the Nile from which it came (itself a bifurcation) dried up, but has since been fed by a new canal to allow water again to make it from the Nile to Al Fayyum. The entire waterway is over 300km long, consisting of modern canals taking Nile water from Asyut to Dairut^[7], the old Nile channel then runs alongside the Nile for over 150km to Lahun, then the Ancient Egyptian canal carries the water into the Fayum Depression.

Torne River has a distributary called the Tärendö River, which on average transports 57% of the water of the Torne River into the Kalix River.^[8]

Goat Island just above Niagara Falls separates the Niagara River into two parts, creating the American and Canadian Falls, but this is too small to be considered a bifurcation.^{[citation needed]}

See also

• Bifurcation lake

References