[This article is based on a presentation held by Michael Abebe in February 2020.]
A dam is a barrier or structure that blocks a stream, river, and waterway to confine and control water flow. Dams are classified according to the materials from which they are built.
Embankment dams, for example, can either be earth-filled or rock-filled. The dam contains more than 50 percent of either soil and gravel-sized or smaller rocks (earth-filled) or cobble-sized or larger rocks (rock-filled).
This type of dams represents about 75 percent of all of the dams in the world. Concrete dams, on the other hand, are mainly constructed from cast-in-place or roller-compacted concrete.
Composite dams are composed of both, with concrete gravity or buttress section in combination with earth-filled or rock-filled embankment sections. Earth filled dams were constructed as far back as 2000 BC. Built from 276 to 303 AD, and restored in 1901, the Minneriya dam in Sri Lanka is the oldest still in use.
Today there are over 60,000 large dams in operation. According to the International Commission on Large Dams (ICOLD), a large dam has a height of over 15 metres or is both between 10 and 15 metres high and has a storage capacity of over 3 million cubic metres (MCM).
A typical swimming pool (25 m x 10 m with an average depth of 1.5 m) would have a volume of 375 cubic metres. For context, 3 MCM is equivalent to 8,000 of such swimming pools.
In comparison, the Grand Ethiopian Renaissance Dam (GERD) is planned to have a reservoir with a volume of more than 74 billion cubic metres, or more than 197 million typical swimming pools.
The Eastern Nile Sub-basin is home to several large and complex dams, with other dams under construction and in the planning phase.
At present, the Eastern Nile countries host more than 30 large dams with a combined total storage capacity of more than 200 billion cubic metres (BCM) (>25 percent of existing African dams’ storage capacity). It is also estimated that more than 300 small dams exist in the Eastern Nile countries.
These dams hold several risks, but the structures can benefit all eastern Nile Basin countries if they are overcome.
“More than 90 percent of the world’s rivers will be fragmented by at least one dam within the next 15 years”, according to a study by researchers at the University of Waterloo and the Université libre de Bruxelles.
90 percent of the world’s rivers will be fragmented by at least one dam.”
The same study investigates the impacts of dams and reservoirs on the earth’s climate, as they “trap nearly one-fifth of the organic carbon moving from land to ocean via the world’s rivers”.
“In similar recent studies, the group of researchers also found that ongoing dam construction impedes the transport of nutrients such as phosphorus, nitrogen and silicon through river networks. The changes in nutrient flow have global impacts on the quality of water delivered to wetlands, lakes, floodplains and coastal marine areas downstream.”
The impact of dams on climate has also been documented. Still, it is essential to remember that humans can also decide how much they want to influence the environment through building dams. Dams are built to be used for irrigation, water supply, energy, or flood control.
Dams can also be multipurpose and be used for two or more of the above purposes. They can also mitigate the effect of floods or droughts, thus contributing to local communities becoming more resilient.
The High Aswan Dam is an excellent example that demonstrates both positive and negative impacts within the Nile Basin.
On the one hand, its consequences include “an explosion of water hyacinth, outbreaks of bilharzia [an infection caused by a parasitic worm that lives in fresh water], polluted irrigation channels and a build-up of sediment inland that would otherwise compensate for coastal erosion from Egypt to Lebanon,” according to Tim Harford’s article on the BBC.
And although they are hailed as a poster child for green economy initiatives and a worthy investment by agencies supporting developing countries, it is essential to recall that dams worldwide are also being removed to limit their disastrous environmental effects.
According to a study by several institutions, including the World Wildlife Fund and the European River Network, up to 30,000 dams are obsolete in France, Poland, Spain and the UK alone. These dams “no longer have a beneficial function for society yet continue to suppress the healthy functioning of our rivers”.
This casts a new light over the Nile Basin area, sparking questions like: Are projects double-checked to ensure that they are all really beneficial? Are the dams fulfilling their promises? Do the risks they pose outweigh their benefits?
Dam safety has two main aspects: the safety of the dam and appurtenant structures; and the safety of the population, property and the environment in the vicinity or downstream of the dam.
Up to 2018, there have been 30 dam failures in Africa alone.
A dam failure is a catastrophic incident when water is uncontrollably released from the structure, often when it is no longer structurally sound.
Up to 2018, there have been 30 dam failures in Africa alone and over 300 failures worldwide, according to ICOLD.
Erosion, defects during the building process or overtopping (water spilling over the top of a dam) can all cause a dam to break down.
Generally, these risks can be alleviated by closely monitoring the building process and performing multiple quality checks. It is also essential to regularly maintain the structure and to be alert to the risks of any pending environmental challenges.
It is crucial to raise the awareness of people living near dams, educating them about emergency plans in the event of dam failure. After all, the toll for local populations can be high: In 2018, the Patel dam in Kenya, a small earth dam used for agriculture, failed after heavy rains and flooding. It killed over 40 people and displaced 500 families.
This tragedy is only a snapshot of the risks posed. With more dams planned in the Nile Basin, it is all the more important to make sure that these legacy structures are built for local people and are not to their detriment.
In the Nile Basin, several issues must be addressed. With the growing number of large and complex dams located along a transboundary river, it is crucial to reassess ageing dams to check they are up to date with current standards to protect people and their environment.
Additionally, institutions and individuals, for example, those responsible for repairing the structures, should also be trained to deal with potential risks posed by dams.
This also entails updating or creating institutional structures responsible for dam management and repairs, both at national and regional levels.
With over 150 million people living in major urban centres along the Nile corridor, the lack of a coordinated system of transboundary dam safety management imminently threatens Nile Basin citizens' survival and well-being.
Any single dam failure in a transboundary river would entail more than economic damage. It would exacerbate social and political instability and complicate regional security.
There are significant challenges and conflicts of interest regarding the rights of use and access to the Nile, a vital resource for local populations.
Legal and institutional mechanisms must be set up.
It comes as no surprise that all parties consider its use and access as key for security, survival and progress. Compromising on such issues can sometimes be interpreted as a failure, and yet, it has become clear that failure to cooperate can trigger violence and abuse, thus extending cycles of mistrust and fear.
Several points are vital for cooperation in managing dams to become a reality. First, weather, hydrology data and forecasting are essential to operate dams properly.
Second, future planning is a priority. Legal and institutional mechanisms must be set up on national and regional levels to agree on cooperative management.
Third, any agreements reached must be flexible enough to allow future operators to deal with unforeseen issues. On this point, it is essential to deal with all stakeholders with clarity, fairness and dialogue.
There are neither regional nor national guidelines for dam operations in Nile Basin countries as of the time of writing. Similarly, a cooperative dam safely regulatory framework is yet to be developed.
Nile Basin countries operate according to different guidelines and standards for building, running and managing dams.
Other gaps are yet to be bridged, especially raising awareness of coordinated dam operation benefits, improving technical and institutional capacities, and encouraging upstream-downstream data exchange to ensure successful coordinated dam operation.
The Nile Basin Initiative (NBI) Eastern Nile Technical Regional Office (ENTRO) ran a cooperative model between the Atbara dam in Sudan and the Tekeze dam in Ethiopia.
With increased data exchange and mutual support, benefits were seen in both countries, running into millions of dollars. Extending this cooperation scenario to more dams and more countries promises a range of advantages, economic and otherwise.
Maybe most importantly, cooperation would reduce water loss, maintain the environment and create a brighter economic future for all involved.