Course
The Orange rises in the Drakensberg mountains along the border between South Africa and Lesotho, about 193 km (120 mi) west of the Indian Ocean and at an altitude of over 3,000 m. While in Lesotho, the river is known as the Senqu and parts of it freeze in winter, because of the high altitude there.
The river then runs westwards through South Africa, forming the south-western boundary of the Free State province. In this section the river flows into first the Gariep Dam (the largest in the country), and on to the Vanderkloof Dam. From the border of Lesotho to below the Van der Kloof 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, the Orange meets with its main tributary, the Vaal River, which itself forms much of the northern border of the province. From here the river flows further westwards through the arid wilderness of the southern Kalahari region and Namaqualand in the Northern Cape Province to meet with Namibia at the 20th degree of east longitude. From here it flows westwards for 550 km, forming the international border between the province and Namibia's Karas Region. On the border, the river passes the town of Vioolsdrif, the main border post between South Africa and Namibia.
In the last 800 km (500 mi) of its course the Orange receives many intermittent streams and several large wadis 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 Hundred Falls or Augrabies Falls are located on this section of the Orange, where the river descends 122 m (400 ft) in a course of 26 km (16 mi).
The Orange empties into the Atlantic Ocean at Alexander Bay, which lies about equidistant between Cape Town and Walvis Bay. Some 33 km (21 mi) from its mouth it is completely obstructed by rapids and sand bars and is generally not navigable for long stretches.
The river has a total length of 2,200 km (1,400 mi).
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