Gift Of The Rains: Africa's Great Rivers

In the desert wilderness of Namibia, on southern Africa’s western coast, an unusual river lies hidden beneath the scorching sand for most of the year. It is an ephemeral river – a river that flows above ground for only a few days a year. The water that feeds the Hoanib River collects in the mountains of north-western Namibia. Its course cuts through the desert, travelling mainly underground all the way to the Atlantic Ocean where its waters fan out into a lagoon. Only when exceptional rains fall over the mountains does the water in the lagoon rise enough to break through to the sea. The animals that live here have learned to adapt to the harshness of the desert, where both food and water is scarce. But, although the river flows underground, it provides enough moisture close to the surface to support a thin oasis of trees and bushes. When the rains fall over the mountains the gush of water replenishes the Hoanib. The abundance of water flowing over the desert is short-lived, in just a few days it all seeps into the ground and the plants and animals of the desert have to rely once more on their skills to survive in one of the harshest environments on Earth.

Africa’s landscape is sculpted by some formidable rivers and the Zambezi is one of the continent’s mightiest. It is a river to which man has attributed a spirit of its own. Its course is marked by the Victoria Falls – one of the natural wonders of the world – as well as two dams, of which Kariba is as large as the country of Wales. But the heart of this formidable river lies in the Zambezi Valley, a wild area protected from civilization by tsetse fly infestation and the creation of two national parks that stretch into two countries. Through rain and drought, from summer to winter, the animals of the Zambezi Valley find refuge along this section of the river as well as a guaranteed source of food and water. But these waters harbor dangers too. Crocodiles are always on the alert for prey and beneath the surface tigerfish, like the crocodiles, are accomplished hunters.

Hidden between the mountains of Africa’s Rift Valley flows a majestic river that brings an abundant surge of water to the Luangwa Valley. But this abundance does not last throughout the year, changing dramatically between summer and winter from a full-flowing river to a muddy trickling stream. During this dry period life for the animals that live along this river becomes a constant struggle. Hippos are pushed closer and closer together until violent fights break out. Animals are drawn to river from the surrounding valley, to find water and food. For many, it becomes a deadly trap. But for the lions of the Luangwa this is a time of plenty, as they take advantage of the trapped animals. After six months of no rain, life for the animals becomes extremely desperate. Just as there seems to be no hope of survival, the clouds gather over the mountains and rain brings relief to the Luangwa Valley and its inhabitants. Almost overnight the river fills to its full majesty and all is well in this forgotten valley hidden between the mountains of Africa’s Rift Valley.

One of Africa’s most remarkable rivers spreads its waters over the desolate plains of the Kalahari Desert, forming the largest inland delta on Earth, the Okavango. Fed by the summer rains that fall over southern Angola, the Okavango River flows into the heart of the desert in Botswana. The water flows slowly over the flat expanse of the Kalahari and fans out into shallow lagoons and wide floodplains. Water plants germinate in the newly flooded lagoons and provide food for many water birds. At this time, several bird species such as marabou storks and herons breed and raise their young, living side by side in heronries. As the floodwaters recede, African skimmers also breed, hatch and fledge their brood. In the shrinking channels of the delta, thousands of fish are chased out of hiding by barbel weaving among the reeds. The fish are also caught by egrets, storks and herons from above. Another predator which benefits from the barbel run is the Cape clawless otter, which preys on the barbel themselves. As the water recedes further, the desert reclaims its land, except for a few permanent streams and lagoons. Eventually, the summer rains replenish the Okavango, and the delta once again becomes a bountiful oasis.

The seasons bring life to the valleys forged by the African rivers, but they also play a part in nature’s tragedies. For most of the year, the Mara River flows peacefully through the wide grass plains of Southern Kenya, but during the dry months it displays the ultimate life-and-death struggle: the crossing of hundreds and thousands of wildebeests. The great herds migrate from the south to their winter grazing grounds on the western bank of the river. The zebras are the first to brave the crossing of the Mara, despite the danger from the crocodiles. After a meager diet of barbel, the crocodiles feast. Then the huge wildebeest herds arrive at the Mara’s banks. Driven by instinct, they too forge the crocodile-infested river. After a grueling river crossing, the wildebeests finally reach their winter pastures. They remain here until the summer rains prompt them to return to the Serengeti, but this involves crossing the Mara once more.

The quest to find the source of the Nile built and shattered explorers’ dreams for centuries, until it was eventually discovered that the river’s birthplace is Lake Victoria. The first part of the great river is called the Victoria Nile; it connects Lake Victoria to Lake Albert through a series of rapids and the powerful Murchison Falls. Nile crocodiles have been using the banks of the river as nesting sites for centuries, showing a nurturing side unique in the reptile world. Dikkops nest near the crocodiles, for protection from scavengers such as monitors. The endemic shoebills hunt along the marshy edges of islands in the wide river. A herd of elephants come to these reed-covered islands to feed, where there is easily accessible food for a calf with a mutilated trunk. The islands, and the banks of the river, form the traditional mating ground for Ugandan cobs. The Victoria Nile is also a convenient stopover for migrating Abdim storks. In this part of Equatorial Africa, seasons do not affect the flow of the river, which continuously provides a stable home for its inhabitants.

The Shire River is one of the few African rivers that flows steadily and peacefully throughout the year. It flows serenely through southern Malawi, fed by the abundant waters of Lake Malawi. The lake contains more fish species than any other lake in the world. When the Shire River leaves Lake Malawi, the Great Rift Valley is no longer a deep gorge, and the river flows placidly in a wide valley. Winter is usually a time of drought in Africa, but the Shire is fed by the constant supply of water from the lake, offering a constant abundance to the birds and animals that inhabit its banks. Hippos, crocodiles and waterbuck adorn the banks, and elephants migrate to the river during the dry season. All year round, this is home to one of the biggest fish eagle populations in Africa. The Shire is a river of plenty and fertility. It is a breeding haven for many creatures, from hippos to water monitors to birds such as bee-eaters and whitebreasted cormorants.

The Sand River is shorter and smaller than many of Africa’s rivers, but it has great importance because it supports such an abundance of wildlife. The river is born in the Drakensberg Mountains in South Africa, flowing for 80 kilometers until it joins the Sabie River. In winter the river runs at its lowest, exposing the sandbanks that give it its name. At this time, the Sand is the only source of water for the buffalos, elephants and other animals of the area. The lions also stay close to the river, knowing that their prey must pass regularly through their territory. When the summer rains arrive, the river swells and floods, the only time of year when the elephants can submerge their whole bodies. Soon the Sand settles down to a steady rich flow, which continues through the summer. Through summer and winter, the Sand River enriches the diversity of creatures that make their home in its waters and along its banks.

The Limpopo River in Southern Africa is a giant, not only in its size, but also in the wealth of animal life it supports. In the dry season, the river is the only source of water for many animals, from the giants such as elephants to the smaller creatures. Other giants of the Limpopo include predators such as the python, the largest snake in Southern Africa, and the leopard, which is both the largest spotted cat and the largest solitary hunter. The river is a lure for their prey, particularly in winter. At this time of year, the slow-moving river becomes an ideal habitat for algae, which is enjoyed by the tilapia and other fish. When the rains come in summer, the Limpopo swells to giant proportions, saturating its floodplain. Now there is water available further away from the river, and the animals are able to disperse to the valley.

The Rufiji River flows through Tanzania in East Africa, through the vast Selous Game Reserve – the largest reserve in the whole of Africa. It is home to a variety of creatures such as the unique Selous wildebeest, and is a precious haven for endangered animals such as elephants and wild dogs. The river flows all year round, always faithfully providing an ample supply of water. However, food is scarce for the herbivores during the long dry season, and hippos are forced to leave the water for long periods to graze enough of the sparse vegetation on the banks. The animals that depend on the generous river for their food, such as water mongooses, waterbirds and crocodiles, are much less affected by the drought. The predators are also very well fed, and winter is the wild dogs’ peak breeding season, when hunting is easiest. There are two rainy seasons in Tanzania. The first to arrive are the short rains, which only last for a few weeks and do not bring much relief to the vegetation, as most of the water runs off without penetrating the soil properly. The long rains finally come three months later. The Rufiji fills and the valley flourishes and blooms once more.

At the southern tip of Africa, the Olifants River flows through and nourishes the unique Cape Floral Kingdom. Despite being the smallest of the world’s six plant kingdoms, it is the richest and most spectacular, containing 3% of all the plant species found in the whole world. When the spring comes after the winter rainfall, the Cape Floral Kingdom comes to life in a magnificent display of color. Insects flourish, breed and feed on the abundant food, while ants disperse the seeds of many plants. Many rare fish that occur nowhere else in the world find a safe home in the Olifants River’s clear unpolluted waters. Halfway down its course, the river fills the Clanwilliam Dam. From the dam to the sea, the Olifants is bordered with man-planted alien vegetation and cultivated lands. Nonetheless, the mouth of the river remains beautifully pristine and true to nature, attracting a rich variety of waterbirds such as common terns, kelp gulls and pelicans.

When in flood, the Pongola River creates a whole new wild world of quiet backwaters, hidden animals and ancient rituals. The river is born in the Drakensburg, and flows through one of the most remote parts of South Africa – Maputaland. With the summer rains, the Pongola floods, filling its pans, which are home to hippos, great white egrets and goliath herons. Cane rats live in the lush vegetation along the banks, unseen by the warthogs and other creatures that also inhabit the area. Terrapins come to the muddy banks to lay their eggs. Migrating white pelicans visit when the pans are at their lowest and the fish are concentrated into schools. Crocodiles winter in the pans, but return to the river itself year after year to breed. Openbilled storks hunt in the quiet shallows of the river. In order to reach their spawning grounds, redbreasted tilapia battle across a man-made causeway in the feeder channel, making their way between crocodiles, herons and other predators. The Pongola River and its pans are a valuable habitat to many species dependent on this generous river.

The Ogooue River flows throughout the year through the lush tropical rainforest of Gabon in West Africa. The country is an unspoiled wildlife haven where nature is almost untouched by humans, providing a precious refuge for endangered primates such as western lowland gorillas, chimpanzees and black colobus monkeys. Other magnificent inhabitants of the evergreen equatorial jungle include forest elephants and forest buffaloes, which are both smaller than their cousins found in the grassland areas of Africa. The Ogooue River hosts all three of the species of crocodile found in Africa – the well-known Nile crocodile, the diminutive dwarf crocodile and the slender-snouted crocodile. The quieter areas of the river are also home to other underwater hunters such as spotted-neck otters. The river ends in an expansive delta, a rich part of the river where migrant seabirds stop to replenish their reserves during their long journey.