The Okavango Delta is a vast inland delta in northern Botswana. It forms where the Okavango River, which rises in the highlands of Angola and crosses a strip of Namibia, spreads into a tectonic trough in the Kalahari at 930–1,000 m above sea level and never reaches the sea. Each year about 11 km³ of water floods 6,000–15,000 km² of channels, lagoons, papyrus swamp, grassland and thousands of islands, and almost all of it evaporates or is taken up by plants. The east of the delta is protected as the Moremi Game Reserve. On 22 June 2014 the Okavango Delta became the 1,000th site on UNESCO's World Heritage List. What makes it unusual is its timing. The flood peaks in June to August, in Botswana's dry winter, months after the rain that caused it has stopped. The clearest way to understand the delta is to follow one water year from start to finish.
December to March: Rain Falls in Angola and Over the Delta
The water year begins far to the northwest. The Okavango system is formed by the Cubango and Cuito rivers, which rise at about 1,300 m in the sandy highlands of Angola. In 2023 the National Geographic Okavango Wilderness Project traced most of their water to a peatland it calls the Angola Highlands Water Tower. It holds an estimated 423 km³ of water and supplies more than 95% of the basin's flow, and in 2026 Angola listed it as the country's first Ramsar wetland. Angola gets about three times as much rain as Botswana in the wet season, and most of it falls in January and February. That rain is the source of the coming flood.
The delta gets rain in the same months, but much less of it. Its average is about 450 mm a year, roughly a third of what its Angolan catchment receives, and it falls mostly between December and March as heavy afternoon thunderstorms. December to February is hot, with daytime highs up to 40 °C and humidity between 50% and 80%. The local rain turns the dry woodland and island grasses green. This is still the low-water season in the delta's channels, because the Angolan floodwater has not arrived yet.
March to June: The Flood Moves From Mohembo Toward Maun
The Angolan floodwater takes about a month to travel the first 1,000 km of the river. Just before reaching Botswana it drops 4 m over the rapids at Popa Falls in Namibia, which are best seen when the river is low. It enters Botswana at Mohembo, at the top of the Panhandle, a narrow, swampy valley where the river is still confined before it fans out. From there it spreads across the delta between March and June. It covers the final 250 km or so in about four months, working its way through papyrus and reed beds and a network of channels including the Nqoga, Jao, Boro, Thaoge, Santantadibe and Maunachira.
The flood moves so slowly because the land is almost flat. Over 15,000 km², the height of the surface varies by less than 2 m, while the water drops only about 60 m in total between Mohembo and Maun. Because the slope is so small, a little sand building up in one channel can send water down another. The Okavango carries almost no mud, only clear water and sand. Plants along the channel edges trap the sand, building up the banks and forming new islands where more plants can take root. As March turns to May, temperatures fall to daytime highs of about 30 °C, the last storms stop, and the dry floodplains begin to flood.
June to August: Peak Flood in Botswana’s Dry Winter
The flood peaks between June and August, when almost no rain is falling. Maun averages 1 mm in June, 0.5 mm in July and none in August. At its peak the delta swells to about three times its permanent size. Days are mild, but nights can drop to just above freezing, and frost sometimes forms. Elsewhere in Botswana the pans and waterholes are dry by now, so animals come into the delta from far around. This is when it holds one of Africa's largest concentrations of wildlife.
All of the Big Five live here: lion, leopard, African buffalo, African bush elephant and rhinoceros. The red lechwe, an antelope, is the most common large mammal, with about 88,000 animals. Sitatunga, hippos and Nile crocodiles live here too, and there are 71 fish species, from the 1.4 m sharptooth catfish to the 3.2 cm sickle barb. The same fish species live in the Zambezi, which shows the two rivers were once connected. More than 400 bird species have been recorded, including Pel's fishing owl, the African skimmer and the wattled crane. Since 2005 the delta and Zimbabwe's Hwange National Park have together been treated as one Lion Conservation Unit.
Chief’s Island and the Salt Islands at High Water
When the water is high, the islands are where land animals find dry ground. The largest, Chief's Island, was pushed up along a fault into a block more than 70 km long and 15 km wide. It was once a hunting ground reserved for the chief. Today it lies within the Moremi Game Reserve and is the core refuge for the delta's resident wildlife during the flood. Moremi, proclaimed in 1963 and named after Chief Moremi III of the Batawana, covers just under 5,000 km² and belongs to the five-country Kavango–Zambezi Transfrontier Conservation Area.
Most of the thousands of smaller islands began with termites. About 70% started as termite mounds, often built by Macrotermes, on which a tree took root. As plants take up water, salt builds up around their roots, and over time this makes the centre of an island too salty for plants. The result is a bare white patch, sometimes with a single salt-tolerant palm, surrounded by a ring of trees and grass on the less salty edges. Seen from the air, these pale centres show up across the delta.
September to November: Retreating Water and October Heat
From September the heat builds again. As the flood drains away or soaks into the sand, the floodplains dry out first. Water stays in the main channels, in riverbeds and waterholes, and in large lagoons, and these draw more and more animals as the season goes on. October is the hardest month. Daytime temperatures often go above 40 °C, Maun gets on average just 17 mm of rain, and the dry spell breaks only with the odd sudden storm. In November the first proper storms arrive and the cycle starts again.
Not every year follows the same pattern. Because the delta is so hot, evaporation and transpiration are rapid, and they produce three cycles of rising and falling water levels, which scientists did not fully understand until the early 20th century. Floods are also much bigger in some years than others. In very wet years, water can flow out of the northeast of the delta along the Magweggana and reach the Zambezi, bypassing the Kalahari.
Molapo Fields, Maun and the People of the Flood
People have organised their year around the flood for centuries. Five groups live in and around the delta. The Hambukushu, Dceriku and Wayeyi have traditionally combined millet and sorghum farming with fishing, hunting, gathering and herding. The Bugakhwe and ǁanikhwe, who are Bushmen, have lived by fishing, hunting and gathering. The Batawana, a Tswana people, have controlled the delta politically since the late 18th century and took full control in the 1850s, when the ivory trade boomed. Most Batawana lived on the delta's edges because tsetse fly kills cattle. When the tsetse retreated, they lived in the swamps from 1896 until the late 1930s.
The main crop system follows the falling water. When the flood retreats from the lower delta, it leaves damp soil called molapo, where farmers plant crops and fodder. When floods were unusually high from 1974 to 1978, the water did not retreat in time, there was no planting season, and food and fodder ran short. The Molapo Development Project that followed built bunds with sluice gates so farmers could hold back floodwater and release it when they were ready to plant.
Maun, founded in 1915 as the Batawana capital on the Thamalakane River, had 85,293 people in 2022 and is the base for the safari industry. Botswana runs the delta on a high-cost, low-volume tourism model. A 2014 UNESCO report counted 2,129 tourist beds, and in 2017 the delta had 52,638 visitors. Poaching hit hard in 2020 and 2021, when 92 rhinos were killed and the government moved the survivors out of the delta.
Where the Water Ends: Thamalakane, Boteti and Lake Ngami
Only about 2–4% of the water that enters the delta flows out of it, through the Thamalakane and on into the Boteti, which in high-flow seasons reaches the Makgadikgadi Pans. Some water also fills Lake Ngami, which David Livingstone saw as a large, open lake in 1849 and which has shrunk a great deal since 1890. Lake Ngami is one of the remnants of the ancient Lake Makgadikgadi, which once covered the delta area too and had mostly dried up by the early Holocene. The future of the water year depends on decisions made upstream. Namibia has proposed a hydropower station that would partly regulate the flow, ReconAfrica's exploration in the wider basin reported oil deposits in April 2021, and climate models project less rain and higher temperatures across the catchment. To follow the river from its Angolan source, read our Okavango River guide. For the wider basin it ends in, see our article on the geography of the Kalahari Desert, and for the rest of the country's animals, see our overview of wildlife in Botswana.