Editing Orange River (section)

===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.