The Orange River is the largest river in South Africa, flowing through three countries – Lesotho, South Africa, and Namibia. It is about 2,200 km long and is an important source of drinking water, as well as being used to irrigate agricultural land. The river begins in Lesotho, then flows through South Africa and Namibia where it empties into the Atlantic Ocean.
South Africa’s Longest River
The Orange River, also known as the Gariep, Groot and Senqu, is the longest river in South Africa.
The river has its source in the Maluti, Taba Putsoa and Dragon Mountains at 3,350 m on the border between the Kingdom of Lesotho and the South African province of KwaZulu-Natal. This mountainous region is very extensive and high rainfall: the headwaters of the Orange River are fed by rainwater, which they collect over an area of 30 thousand km2.
In its upper and middle reaches, the Orange forms numerous rapids and waterfalls. The largest of them is Aughrabis Falls, 146 m high.
The river overcomes rocky rocks along its entire length. In places where the rocks are more pliable, wide open areas and valleys are formed. In places with magmatic rock the channel narrows and forms gorges, which makes it possible to build hydroelectric power plants and reservoirs.
The Orange River flows into the Atlantic Ocean. During those periods of the year when the current is too weak, the estuary is blocked for a long time by a sand berm, washed up by the waters of the river and only destroyed during high floods. The strip of sandy sediments and rifts stretches for 33 km upstream from the mouth of the river.
The Orange is characterized by a phenomenon not often seen in African rivers: the surge of sea water at the mouth is not uncommon and it rises quite high up the riverbed.
Almost its entire length of the river flows through areas with extremely hot and dry climate: the arid High Veld region, the Kalahari and Namib deserts. In general, the entire Orange basin can be called desert, as some areas receive less than 25 mm of rainfall per year.
During the dry season, the water level in the river decreases due to rapid evaporation. But during the rainy season, the Orange turns into a swift brown stream. The reason is that more than 2000 mm of precipitation falls at the source of the river and less than 50 mm at the mouth. The significant height difference generates a rapid flow of the river.
The first researcher who mapped the river in 1777-1779 was Robert Gordon, a Scottish officer of the Dutch army and commander of the Cape Town garrison. He named the river after William V of Orange and the Orange dynasty who ruled Holland at the time.
The Orange differs from the other great African rivers in that it is not navigable either at the mouth or in any other section: there are many rapids and fast currents in the upper reaches, while the lower reaches are full of shoals and rifts. In its upper reaches, however, it serves as a natural boundary between the northern and southern provinces of South Africa as well as between South Africa and the Kingdom of Lesotho, while in its lower reaches – between Namibia and South Africa.
Although the river has never had any major cities on it, it plays an important role in South Africa’s economy, providing water for agricultural areas for irrigation as well as for the construction of hydroelectric power plants. The main obstacle to hydropower development is the large amount of river sediment – sand and silt – that quickly clogs the stretch of river where the hydroelectric facilities are located.
The Orange River is home to Gariep, the largest dam and reservoir of the same name in South Africa, and Vanderkloof, the second largest dam. Below these two structures, the current becomes calmer, the river flows through the plain and is mostly disassembled for irrigation.
Diamonds and gold
The second wealth of the river are the diamond deposits in its lower reaches. All of them are located on a stretch of only 100 km from the mouth of the river, where there are several diamond mines. Orange River diamonds are what is known as alluvial: they are washed right out of the river sand. One third of all South African gold is mined right here in the river valley.
Tourism is less developed on the Orange River because of the unusually hot climate. But since there are no large predatory animals in the river valley (even the unpretentious crocodiles do not survive in winter) and the water level in the summer is quite high, the river is a favorite place for rafters – fans of rafting in extreme conditions.
The people who live on the river are mainly engaged in the cultivation of some kinds of grains, fruits and vegetables, as well as raising small livestock for their own needs.
- Location: South Africa.
- Flows through: the Kingdom of Lesotho, the Republic of South Africa, the Republic of Namibia.
- Feeding method: rainwater.
- Mode: Flood.
- Source: the Maputi Mountains, the Taba-Putsoa Mountains and the Dragon Mountains (Kingdom of Lesotho).
- Mouth: Atlantic Ocean, Alexander Bay city (South Africa).
- Major tributaries: right tributaries – Caledon, Vaal, Fish River.
- Major population centers: Apington (South Africa) – 60,000 (2001), Prisca (South Africa) – 11,236 (2001), Alival-North (South Africa) – 8,542 (2001).
- Length: 2,200 km.
- The area of the basin is 973,000 km2 .
- Average water flow rate: 800 m3/sec.
- Average annual flow: 25 km3.
- Solid runoff: 153 million tons.
- Irrigated area: 294,000 km2.
- Headwaters elevation: 3,300 m.
- Highest water level: November-March (peak February-March).
- Lowest water level: July-August.
- Hydroelectric power stations.
- Water reservoirs.
- Minerals: gold, diamonds.
- Industry: mining industry.
- Agriculture: irrigation farming.
- Services sphere: tourism, transport.
Climate and weather
- Average temperature of January: +26°C.
- Average temperature of July: +13°C.
- Average annual rainfall: up to 2,000 mm in the upper reaches and 50-230 mm in the Namib desert.
- Dragon Mountains: cave paintings of bushmen.
- Kalahari Desert, the Namib Desert.
- Augrabis Falls and Augrabis National Park.
- The Gariep and Vanderloof dams.
- City of Alexander Bay: mouth of the Orange River.
- Richtersveld National Park (northern South Africa).
- Alexander Bay, a South African town at the mouth of the Orange River, is the northernmost town on the west coast of South Africa. Outsider access to the area is restricted, as this is where South Africa’s diamond mines are concentrated.
- On the territory of the Kingdom of Lesotho, the sources of the Orange River are above 3,000 m, and for this reason in some sections they freeze in the cold season.
- In the Dragon Mountains there is the largest collection of Bushmen drawings on the walls of the caves: 35000-40000. The oldest were made by Bushmen 2,400 years ago.