The Okavango Delta, also called the Okavango Grassland, is a large inland delta in Botswana. It forms where the Okavango River flows into a deep area of the Earth’s crust at an elevation of 930–1,000 meters (3,050–3,280 feet) in the central part of the Kalahari Desert’s basin, which does not drain into the ocean.

It is a UNESCO World Heritage Site because it is one of the few inland delta systems that do not flow into the sea or ocean. The wetland system remains mostly undisturbed. All the water that reaches the delta is eventually lost through evaporation and released by plants. Each year, about 11 cubic kilometers (2.6 cubic miles) of water spread across an area of 6,000–15,000 square kilometers (2,300–5,800 square miles). Some floodwaters flow into Lake Ngami. The area was once part of Lake Makgadikgadi, an ancient lake that dried up by the early Holocene era.

The Moremi Game Reserve is located on the eastern side of the delta. The delta was named one of the Seven Natural Wonders of Africa, which were officially announced on 11 February 2013 in Arusha, Tanzania. On 22 June 2014, the Okavango Delta became the 1,000th site added to the UNESCO World Heritage List.

Geography

The Okavango Delta is formed by seasonal flooding. The Okavango River carries water from summer rains in the Angola highlands. This water travels about 1,200 km (750 mi) in one month. Over the next four months (March–June), the water spreads across the delta, covering an area of 37,500 km² (14,500 sq mi).

The high temperatures in the delta cause water to quickly evaporate and be lost from plants. This leads to three cycles of rising and falling water levels. Scientists did not fully understand these cycles until the early 20th century. The flood reaches its highest level between June and August, during Botswana’s dry winter months. At this time, the delta grows to three times its usual size, drawing animals from far away and creating one of Africa’s largest wildlife areas.

The delta is very flat, with less than 2 m (7 ft) difference in height across its 15,000 km² (5,800 sq mi) area. However, the water drops about 60 m (200 ft) from Mohembo to Maun.

Salt builds up around plant roots in the center of many islands, making those areas too salty for most plants to grow. Only a few salt-resistant palm trees can survive there. Trees and grasses grow on the edges of islands where the soil is not as salty.

About 70% of the islands began as termite mounds (often Macrotermes spp.). Trees later grew on these mounds, forming islands.

Chief’s Island (19°12′S 22°48′E / -19.200; 22.800), the largest island in the delta, was created by a fault line that lifted an area 70 km (43 mi) long and 15 km (9.3 mi) wide. In the past, it was a special hunting area for a chief. Today, it is a protected wildlife area. It serves as a key habitat for many animals when the water levels rise.

Climate

The Delta's many green plants are not because of a wet climate. Instead, it is a place with water in a dry area. The average yearly rainfall is 450 mm (18 inches), which is about one-third of the rainfall in its Angolan catchment area. Most of this rain falls between December and March as heavy afternoon thunderstorms.

December to February are warm and wet months. Daytime temperatures can reach 40 °C (104 °F), and nights are warm. Humidity levels range from 50% to 80%. From March to May, temperatures drop. Days are up to 30 °C (86 °F), and nights are mild or cool. The rain stops quickly, leading to the dry, cool winter months of June to August. During this time, days are mild to warm, but temperatures drop greatly after sunset. Nights can be cold, with temperatures just above freezing. Sometimes, frost appears in the delta during winter.

From September to November, heat and pressure increase again as the dry season moves into the rainy season. October is the hardest month for visitors. Daytime temperatures often go above 40 °C (104 °F), and the dryness is sometimes broken by sudden heavy rain.

Fauna of the delta

The Okavango Delta provides a home for many animals all year round and during certain seasons. The five largest African game animals—lion, leopard, African buffalo, African bush elephant, black and white rhinoceros—live there.

The most common large mammal in the area is the lechwe, with estimates showing about 88,000 lechwe live there. Other animals include giraffe, blue wildebeest, plains zebra, hippopotamus, impala, common eland, greater kudu, sable antelope, roan antelope, puku, waterbuck, sitatunga, tsessebe, cheetah, African wild dog, spotted hyena, black-backed jackal, caracal, serval, aardvark, aardwolf, bat-eared fox, African savanna hare, honey badger, crested porcupine, common warthog, chacma baboon, vervet monkey, and Nile crocodile.

The delta also supports over 400 bird species, such as helmeted guineafowl, African fish eagle, Pel’s fishing owl, Egyptian goose, South African shelduck, African jacana, African skimmer, marabou stork, crested crane, African spoonbill, African darter, southern ground hornbill, wattled crane, lilac-breasted roller, secretary bird, and common ostrich.

Since 2005, the protected area has been part of a Lion Conservation Unit along with Hwange National Park.

By 2019, about 150 rhinoceroses lived in the northern Okavango Delta. From 2020 to 2021, 92 rhinos were killed by poachers in the region, leaving only 40 individuals. This led the government to move the remaining rhinos to a safer location.

The Okavango Delta is home to 71 fish species, including tigerfish, tilapia, and various catfish. Fish sizes vary from the large African sharptooth catfish, which can grow up to 1.4 meters (4.6 feet), to the small sickle barb, which is only 3.2 centimeters (1.3 inches) long. These same fish species are found in the Zambezi River, showing a historical connection between the two river systems.

Flora of the delta

The Okavango Delta has 1,068 types of plants that belong to 134 families and 530 groups. Five main plant groups live in the area that is always wet: Papyrus cyperus grows in deeper water, Miscanthus lives in areas with shallow water, and Phragmites australis, Typha capensis, and Pycreus grow in between. Plants that are common in the always-wet areas also grow in places that flood seasonally. Papyrus cyperus reeds grow best in slow-moving water that is not too deep and are often found along river channels. On islands and the edges of land near flooded grasslands, different plant groups live. These plants are found based on how much water they need. For example, Philenoptera violacea needs very little water and grows at the highest points in the always-wet areas. It is often found on dry islands that flood seasonally. Trees that only grow on islands in the always-wet areas include the palm Hyphaene petersiana and acacia trees.

The plants in the delta help hold the sand together. River banks usually have a lot of mud, which mixes with sand from the river to build up the banks. However, the Okavango River has very little mud because its water is clean. Instead, plants trap the sand, acting like glue to replace the missing mud. This process helps create new islands where more plants can grow.

This process does not form long, thin islands that curve like rivers. These islands are actually the old riverbanks of paths the river once followed. Over time, plants and sand blocked these old paths, causing the river to change course. The old riverbanks then became islands. Because the delta is very flat and receives a lot of sand from the Okavango River, the land slowly rises over time. Areas that are now river channels may one day become islands, and new channels may later wash away these islands.

People

The people of the Okavango Delta include five ethnic groups, each with its own culture and language:

• the Hambukushu (also called Mbukushu, Bukushu, Bukusu, Mabukuschu, Ghuva, Haghuva),
• the Dceriku (also called Dxeriku, Diriku, Gciriku, Gceriku, Giriku, Niriku),
• the Wayeyi (also called Bayei, Bayeyi, Yei),
• the Bugakhwe (also called Kxoe, Khwe, Kwengo, Barakwena, G|anda),
• the ǁanikhwe (also called Gxanekwe, ǁtanekwe, River Bushmen, Swamp Bushmen, Gǁani, ǁani, Xanekwe).

The Hambukushu, Dceriku, and Wayeyi have lived by farming millet and sorghum, fishing, hunting, gathering wild plants, and raising livestock.

The Bugakhwe and ǁanikhwe are groups known as Bushmen. They have traditionally fished, hunted, and gathered wild plants. The Bugakhwe used both forest and river resources, while the ǁanikhwe mainly used river resources. The Hambukushu, Dceriku, and Bugakhwe live along the Okavango River in Angola and in the Caprivi Strip of Namibia. Small numbers of Hambukushu and Bugakhwe also live in Zambia. In the Okavango Delta, the Hambukushu, Dceriku, and Bugakhwe have lived in the panhandle and the Magwegqana area in the northeastern part of the delta for about 150 years. The ǁanikhwe have lived in the panhandle, along the Boro River through the delta, and along the Boteti River.

The Wayeyi have lived near Seronga and in the southern delta around Maun. A few Wayeyi also live in their original homeland in the Caprivi Strip. In the past 20 years, many people from across the Okavango Delta have moved to Maun. In the late 1960s and early 1970s, over 4,000 Hambukushu refugees from Angola were settled near Etsha in the western Panhandle.

The Okavango Delta has been controlled by the Batawana, a group from the Tswana people, since the late 1700s. Led by Mathiba I, a leader from a group related to the Bangwato, the Batawana took full control of the delta in the 1850s as the ivory trade grew. Most Batawana have traditionally lived near the edges of the delta because the tsetse fly, which harms their cattle, is a danger in the center. For about 40 years, the tsetse fly population decreased, and many Batawana lived in the swamps from 1896 until the late 1930s. Since then, the edges of the delta have become more crowded as more people and livestock move there.

Molapos(water streams)

After the flood season ends, water in the lower parts of the delta, near the bottom, dries up, leaving wet soil behind. This leftover water helps farmers grow crops like fodder and other plants that need moisture. This type of land is called molapo in the local language.

Between 1974 and 1978, floods were stronger than usual, making it impossible to grow crops after the water receded. This caused serious shortages of food and fodder. To solve this problem, the Molapo Development Project was started. The project built bunds, which are earth barriers, around molapo areas to manage flooding and stop severe floods. These bunds include sluice gates, which allow stored water to be released so farmers can begin growing crops again after the floodwaters go down.

Possible threats

One possible threat comes from oil exploration by the Canadian company ReconAfrica. In April 2021, initial exploration found oil deposits in sedimentary rock. Environmentalists are worried the project might harm the environment and threaten some of the main water sources. ReconAfrica has said, "There will be no damage to the ecosystem from the planned activities."

The Namibian government has proposed building a hydropower station in the Zambezi Region, which could control the flow of the Okavango River to some degree. Supporters claim the impact would be small, but environmentalists believe the project might harm most of the area’s diverse plant and animal life in the delta. Other threats include human activity expanding into the region and water being taken from the area by people in Angola and Namibia.

In the 1980s, South African filmmaker and conservationist Rick Lomba warned about the risk of cattle overpopulation harming the area. His documentary, The End of Eden, showed his efforts to protect the delta.

The Okavango catchment is expected to receive less rainfall each year and experience higher temperatures due to global warming. These changes may reduce the size of floodplains in the Okavango Delta, which could affect water availability, livestock, and farming in the region.

Conservation International Botswana has worked in the Okavango Delta by providing education, engaging with policymakers, and conducting research. This includes aerial wildlife surveys and biological assessments to monitor the area’s health.