Editing Orange River (section)

== Course ==
[[File:Orange River basin map.svg|left|thumb|The course and watershed of the Orange River, Caledon River and Vaal River (ǀHaiǃarib). This map shows a conservative border for the watershed. Specifically, the [[Kalahari]] basin is excluded, as some sources say it is [[endorheic]].<ref name="Swanevelder1981" /> Some other sources using computational methods show a basin which includes parts of [[Botswana]] (and hence of the Kalahari).<ref name="wri">Revenga, C.; Murray, S.; Abramovitz, J. and Hammond, A . (1998) [http://pubs.wri.org/pubs_description.cfm?PubID=2900 Watersheds of the world: Ecological value and vulnerability] {{Webarchive|url=https://web.archive.org/web/20070317061600/http://pubs.wri.org/pubs_description.cfm?PubID=2900|date=17 March 2007}}, ''World Resources Institute'', {{ISBN|1-56973-254-X}}</ref>]]
The Orange rises in the Drakensberg mountains along the border between South Africa and Lesotho, about {{convert|193|km|mi|abbr=on}} west of the Indian Ocean and at an altitude of over {{convert|3,000|m|abbr=on}}. The extremity of the Orange River inside Lesotho is known as the '''Senqu'''. Parts of the Senqu River freeze in winter because of the high altitude. This creates droughts downstream, which mainly affect goat and cattle production.

[[File:Rosh Pinah Orange River.jpg|thumb|Orange River south of [[Rosh Pinah]]]]
[[File:Senqu River in Lesotho.jpg|thumb|Senqu River Near Ha Potomane (Cutting Camp) in Quthing, Lesotho]]
[[File:Orange River near Oranjerivier.jpg|thumb|Orange River near Hopetown]]

The Orange River then runs westward through South Africa, forming the south-western boundary of the [[Free State (province)|Free State province]]. In this section, the river flows first into the [[Gariep Dam]] and later into the [[Vanderkloof Dam]]. From the border of Lesotho to below the Vanderkloof Dam, the river bed is deeply incised. Further downstream, the land is flatter, and the river is used extensively for irrigation.

At the western point of the Free State, southwest of [[Kimberley, Northern Cape|Kimberley]], the Orange meets with its main tributary, the [[Vaal River]], which forms much of the northern border of the province. From here, the river flows further westward through the arid wilderness of the southern [[Kalahari Desert|Kalahari]] region and [[Namaqualand]] in the [[Northern Cape]] province to meet with Namibia at 20°E longitude. From here, it flows westward for {{convert|550|km|mi|abbr=on}},<ref name ="ACWR" /> forming the international border between the province and Namibia's [[ǁKaras Region]]. On the border, the river passes the town of [[Vioolsdrif]], the main [[Border checkpoint|border post]] between South Africa and Namibia.
[[Image:OrangeRiver L7 11apr01.jpg|left|thumb|This image shows the last {{convert|100|km|mi|abbr=on}} or so of the Orange River, in which the gravel deposits in the river bed and along the banks are rich with diamonds, and several diamond mines operate along this stretch.]]
In the last {{convert|800|km|mi|abbr=on}} of its course, the Orange receives many intermittent streams (such as the [[Fish River (Namibia)|Fish River]]), and several large [[wadi]]s lead into it. In this section, the [[Namib]] Desert terminates on the north bank of the river, so under normal circumstances, the volume of water added by these tributaries is negligible. Here, the bed of the river is once again deeply incised. The [[Augrabies Falls National Park|Augrabies Falls]] are located on this section of the Orange, where the river descends {{convert|122|m|abbr=on}} in a course of {{convert|26|km|mi|abbr=on}}.

The Orange empties into the Atlantic Ocean between the small towns of [[Oranjemund]] (meaning "Orange [[river mouth|mouth]]") in Namibia and [[Alexander Bay, South Africa|Alexander Bay]] in South Africa, about equidistant between [[Walvis Bay]] and [[Cape Town]]. Some {{convert|33|km|mi|abbr=on}} from its mouth, it is obstructed by [[rapids]] and [[Shoal|sand bars]] and is generally not [[Navigability|navigable]] for long stretches.

The river has a total length of {{convert|2432|km|mi|abbr=on}}.

===Catchment and rainfall===
[[Image:Augrabie 01.jpg|thumb|The [[Augrabies Falls]] in full flow]]
In the [[dry season]], the volume of the water in the river is considerably reduced because of the rapid run-off and [[evaporation]]. At the [[River source|source]] of the Orange, the rainfall is about {{convert|2,000|mm|in|abbr=on}} per annum, but precipitation decreases as the river flows westward; at its mouth, the rainfall is less than {{convert|50|mm|in|abbr=on}} per year. The factors that support evaporation, though, tend to increase in a westerly direction. In the [[wet season]] (summer), the Orange river becomes a brown coloured torrent. The huge mass of [[sediment]] carried constitutes a long-term threat to engineering projects on the river.<ref>[http://www.orangesenqurak.org/river/subbasins/ephemeral+rivers.aspx?print=1 The Northern Ephemeral Rivers of the Orange-Senqu River Basin]{{Dead link|date=April 2020 |bot=InternetArchiveBot |fix-attempted=yes}}</ref>

The total catchment of the Orange River (including the Vaal) extends over {{convert|973,000|km2|abbr=on}}, i.e. equivalent to about 77% of the land area of South Africa ({{convert|1,221,037|km2|abbr=on}}). Around {{convert|366,000|km2|abbr=on}} (38%), however, are situated outside the country in Lesotho, Botswana, and Namibia.

=== Tributaries ===
* [[Vaal River]] - {{cvt|1,458|km}}
* [[Caledon River]] - {{cvt|642|km}}
* [[Khubelu River]] - {{cvt|144|km}}

=== Dams ===
* [[Armenia Dam]]
* [[Egmont Dam]]
* [[Gariep Dam]]
* [[Newberry Dam]]
* [[Vanderkloof Dam]]
* [[Welbedacht Dam]]