The great rivers of Africa like the Zambezi, the Niger, the Nile, the Rufiji, the Senegal and the Tana have one thing in common – they have spectacular deltas high in biodiversity, with a fascinating array of mangrove forests, sand dunes and floodplains.
Like forests and grasslands, they are also important carbon sinks and have that one special trait - they need the floods to replenish them.
In 2008 Institut de Recherche pour le Développement (IRD) - a French research organisation that addresses international development issues - launched a four-year project to compare the deltas of the Tana River in Kenya and the Rufiji River in neighbouring Tanzania.
“Instead of only comparing the two deltas, we realised that it was better to compare all other deltas in Africa,” explains Dr Stephanie Duvail, the principal research scientist with IRD. “All are facing similar issues like oil exploration, climate change, building dams for hydropower, large scale irrigation, and land-use change.
This resulted in the first Afrideltas conference with a hundred scientists, researchers and scholars from across the continent and across the seas in one room in the Tanzanian capital Dar es Salaam last month.
The beautiful floods
Deltas cannot exist if they are not replenished with water and sediment – it is this dynamic that keeps deltas alive. Harnessing the natural flooding of the deltas, people have since antiquity farmed deltas like the Pokomo in Kenya’s Tana Delta.
For centuries, the Pokomo used a method similar to the pharaohs of ancient Egypt to farm rice. Called recession farming, rice is planted when the plains are flooded. As the water recedes, the rice continues to grow because the rice fields are kept watered using the fresh water bore of the river.
Then at the start of the 20th century, Africa’s first large-scale dam was constructed. The Aswan Low Dam in Egypt is built along the Nile and controls its floods, releasing the water in times of drought to protect the country from famine. Well intentioned, it has created a series of problems.
Before the Aswan dam, the Nile had flooded every year for thousands of years from the East African drainage basin – Lake Victoria, the source of the Nile that is shared between the three East African countries of Kenya, Uganda and Tanzania. The floods carried with them minerals and nutrients that enriched the soils along the floodplain and the delta.
Despite some gains, the disappearance of the annual flooding, and the heavy year-round irrigation that Egypt now relies on has turned the soil more saline and waterlogged, affecting crop yields negatively.
Traditional farming practices, such as recession farming, sustained the ecological balance of deltas around the world and the livelihoods of people for millennia, whereas many modern large-scale projects dependent on dams have failed in the last 50 years.
Despite this, Africa’s rivers and floodplains are being transformed rapidly by humans in search of energy. This relentless search for new sources of energy will change the face of Africa this century as its populace increases coupled with urbanisation - and climate change.
Dam or dam
“Dams in themselves are not bad but they have to be properly designed from the very beginning and managed properly. Most times, the people controlling the dams do not care about the famers and the pastoral people downstream,” says Duvail.
There are very few examples to show that damming can have some positive results.
The Senegal River stretches 1,790km forming the border between Senegal and Mauritania in West Africa. The multi-purpose Manantali Dam was built to tame the river and provide artificial flooding during the dry spell and other ecosystem services to support energy, biodiversity and farming. In some areas, the land did better with the dam but the overall impact has shown diminishing returns.
In Sudan, the Mayan wetlands in Dinder National Park in the last three decades have dried out, negatively affecting wildlife. Two rivers flow through the park – the Rahat and Dinder - between June to November and for the rest of the year they are dry.
“The Mayan wetlands in the park are important wildlife habitats,” states Khalid Hassanballah a civil engineer working in the park. “We’re trying to find out the reason for the drying up of the Mayan wetlands because without them there will be no life in the national park.”
No quick answer
Listening to the Senegalese speaker, one ponders if artificial flooding can replenish the Mayan floodplains as in the case of Manantali dam along the Senegal– which means constructing dams to store excess water during the rains and release it in the dry season.
There is no quick answer but his next comment shows how important a conference like this is. “It’s important to look at the issue not only from an engineering point of view but also from an environment point of view.”
It’s interesting to see this convergence between engineers and environmentalists for, traditionally, engineers have sought out “quick fixes” to problems while environmentalists have sought long-term holistic approaches putting the two at loggerheads.
A big concern also now awaits the fate of Rufiji Delta – the proposed Stiegler Gorge dam. “It will have the capacity to store more water than the entire flow of the Rufiji, generate more electricity than Tanzania’s current demand and electrify Africa but leave 200,000 people vulnerable,” states Dr Olivier Hamerlynck of the Kenya Wetlands Biodiversity Research Team (KENWEB). “It will also dry out most of the lakes along the river that are fed by the Rufiji.”
Leasing the deltas
“In the last ten years, African governments have leased land to foreign countries because most see deltas as unproductive wastelands that can be converted into farmland for rice, sugar cane and vegetables,” states Dr Nathan Gichuki, a Kenyan wetlands expert with 20 years experience.
“The significance of deltas is that they are windows to the evolution of landscapes and mirror landscape change over time because of the sediments that have been deposited over millennia on the floodplains,” he says.
“It’s ironical that while big dams are being decommissioned in developed countries,” remarks Dr Hamerlynck, “Africa is commissioning more. Mega super dams come with so many problems. New Orleans drowned because there was no more sediment for the water to seep through because of the dams built along the Mississippi river.
Legislation review, making science succeed, the urgent need to restore wetlands and long-term international research were some of the recommendations from the African deltas conference.
But if business carries on as usual, millions of people stand to lose their homes and livelihoods as the sea encroaches on the land. But the good news is that there will always be a delta because the sediments need to be stored somewhere – only that it will have moved more inland.
•Rupi writes on environmental and travel issues: Email: [email protected]