Torrential rains, which have been falling for several weeks in the Sahel belt and part of central Africa, are putting pressure on aging and often poorly maintained dams. In northeastern Nigeria, the failure of the Alau Dam on Thursday, September 12, submerged a large part of the city of Maiduguri, located about twenty kilometers to the south. More than 400,000 people have been displaced, thousands of homes and essential health and educational infrastructure have been destroyed.
After remaining deaf to previous warnings, the federal government announced this week the creation of a commission charged with evaluating the status of all the country’s dams. You will also need to perform a complete diagnosis of Alau before your reconstruction.
At the end of August, the collapse of the Arbaat dam in Sudan affected 50,000 people and destroyed – partially or completely – twenty villages, in a humanitarian context already marked by a year of civil war. The city of Port Sudan is deprived of its main freshwater reservoir. These two events echo the tragedy that occurred a year ago in Derna, Libya, devastated by a flash flood caused by the failure of two structures under the weight of a record amount of water carried by Storm Daniel. According to the United Nations, some 6,000 people have died and several thousand remain missing.
Human and financial resources are often lacking
Should we see them as warning signs of other accidents to come? “As a general rule, the risks of dam failure are minimal because safety regulations include the probability of exceptional flooding, but on the African continent many structures are more than fifty years old. These are old infrastructures adapted to a climate that has been transformed with increasingly frequent episodes of abundant and violent rains. Very often the climatic and hydrological hypotheses on which they were designed are unknown. As do their plans, especially in regions in conflict for security reasons. This adds a lot of uncertainty and reduces the possibilities of anticipating disasters. In many cases, the spillways that dams are equipped with to manage water overflows and prevent overflows will not be able to cope.observes Micha Werner, professor at the IHE institute in Delft (Netherlands) and specialist in flood management.
Although the situations vary from one country to another, the researcher points out that there is often a lack of human and financial resources to guarantee the proper functioning of these old infrastructures, whose function is to regulate the flow of water courses and cushion the risks of flooding: “Flood and low water readings are not done regularly and we have less local data than fifteen years ago. However, they are the only ones that can provide us with a good understanding of the risks. »
In extreme cases, the future is simply unknown, as in Sudan, where control of the Jebel Aulia Dam is no longer guaranteed. Located 40 kilometers from Khartoum, in an area held by the rebels of the Rapid Support Forces (FSR), it was abandoned by its employees.
An “urgent” need for rehabilitation
The issue is also a challenge for electricity supply on the continent. In 2019, the International Hydropower Association published a guide to adapting to climate change. Among its recommendations is to take into account long-term climate scenarios developed by climate scientists. Although the guide is not aimed exclusively at Africa, the measures it proposes were tested before being approved in several dam projects, including the Mpatamanga dam in Malawi.
The African Development Bank (AfDB) also examined the issue within the framework of its modernization program for the continent’s hydropower plants adopted in June 2023. This project targets 87 units built more than thirty years ago. Twenty-one of them, representing more than 10% of continental hydroelectric production, need ” urgent “ rehabilitation. “The effects of climate change require additional adaptation measures”underlines the financial institution, citing the reinforcement of flood protection, the improvement of early warning systems and the structural improvement of reservoirs.
If worsening droughts seem to be a real danger for the energy supply of certain countries – as several countries in southern Africa have been experiencing for months – episodes of extreme rainfall fuel the same concern for existing infrastructure. “It is always possible to do safer work. But this work is expensive and is not always within the reach of countries.”says Yves Giraud, former director of EDF Hydro.
This reality has not escaped Ghana. In 2022, the country was one of the first to test its infrastructure against climate change to develop its adaptation roadmap. The exercise revealed that five of its thirty-four dams were threatened, including the Weija dam, which provides 80% of the drinking water supply to the capital, Accra. Its rehabilitation costs hundreds of millions of dollars. A cost that illustrates how much climate change already weighs on the development of the poorest countries like Ghana, as the Minister of the Environment, Kwaku Afriyie, did not fail to underline when presenting his plan to international donors.
