Grand Inga: Will Africa’s Mega Dam Have Mega Impacts?

Kate Showers
Monday, March 5, 2012

Grand Inga would dam the Congo River
Grand Inga would dam the Congo River

Central Africa’s Congo River holds more hydropower potential than any other African river, and the Grand Inga Dam is a grandiose proposal to tap it. Project proponents predict electricity generation more than twice that of China’s Three Gorges. In November, the South African and DR Congo governments signed an agreement to develop the dam. But its outsized price tag (estimated at $80bn) presents a huge roadblock. In February, the $5.2 bn Inga III Dam, also proposed for the Congo, lost its main sponsor in part over project costs; it is now in limbo. Here we excerpt a chapter from the book Engineering Earth (Springer, 2011), which raises concerns about Grand Inga’s environmental impacts, and the potential consequences of its grand scale.

Africa is a mega-continent; it accounts for 20% of the earth’s surface. Its land area is greater than that of China, Europe and the US combined. The Congo River, which empties into the equatorial Atlantic Ocean, is the world’s second largest by flow, after the Amazon. In 1921 the continent was identified as possessing one half of the world’s hydroelectric power potential, with the Congo River basin containing one quarter of it.

What makes the Congo unique among the world’s great rivers is the presence of significant rapids and waterfalls so close to its mouth. The Lower Congo narrows sharply and descends over a series of rapids known as Livingstone Falls. Most of these rapids occur on a straight reach of river. As the river drops its final 96 m to sea level, the channel narrows further and its course makes a sharp 180-degree bend. This is Inga Falls, and it is this unique geomorphic feature that provides the Congo’s greatest hydro-potential – the world’s largest in terms of flow rate. To engineers, the 26 km long curve appears to be two sides of a triangle. They envision adjacent valleys as hypotenuses in which electricity generators could be installed and through which the already confined Congo could be diverted before returning to its normal bed below the falls. This is Grand Inga.

Designs for the Grand Inga Dam have called for a 205m (673 ft) dam wall that will produce a 15 km long reservoir. There are no published estimates of reservoir storage capacity or volume. The Secretary General of the World Energy Council, Gerald Ducet, a major promoter of the project, said the dam would be “substantial, but not among the world’s highest” and “the 15 km long reservoir pales into insignificance in comparison with the Three Gorges Dam project in China and the Volta River scheme in Ghana.” While the dam wall would not be the highest on earth, it would exceed the continent’s highest dam wall, Lesotho’s Katse at 185m, by 20 m. The proposed Grand Inga dam wall would certainly be a mega structure. Because the Congo’s equatorial location means that its flow regime does not have large seasonal variation, a “run-of-river” design was used. (Run-of-river is a loose term to describe hydro projects; it usually means a small dam but not always, and the impacts of such projects can be quite large.)

Grand Inga’s power has never been considered for rural electrification and domestic use. It has only ever been intended for areas of high commercial demand – large cities and industrial areas – and for production of an export commodity. The historical problem of markets for Grand Inga’s electricity was solved by High Voltage Long-Distance (HVDC) transmission technology, regional power pools and a proposed continental grid. By the early 1990s, HVDC lines could transmit electricity for about 6,500 km, and HVAC (High-Voltage Alternating
Current) lines for 4,800 km. Grand Inga’s electricity would be transmitted for very long distances to distant consumers along “export corridors” or “electricity highways.”

Unintended Consequences

Supporters of the project have long argued that social and environmental consequences would be slight for such a large output of electricity. The land around Inga Falls was believed not to have substantial human settlements, and a large impoundment was not imagined. Criticism, largely from the NGO community, raised concerns not only about displaced people, but also about threats to biological diversity posed by the reservoir and unidentified consequences for aquatic ecosystems up- and downstream of the dam.

Environmental reality destroyed an 80-year-old dream of a dam across the Congo. When engineers from WESTCOR – the consortium created by the electricity utilities of Angola, Botswana, Democratic Republic of Congo, Namibia and South Africa – diverted their attention from electrical and construction challenges to actually look at topographical maps, they realized that the original Grand Inga dam design would inundate all low-lying areas in the catchment, creating a massive lake that would flood two major cities: Kinshasa and Brazzaville about 260 km upstream. In addition, the river contained so much sediment that simple calculations showed that the dam would become “packed.” Finally, as the dam reduced the Congo’s flow, salt water from the ocean would intrude upstream for 50 km. causing “irreversible environmental harm to all living matter and organisms at the river mouth.”

Sobered by this “common sense appraisal,” the engineers concluded that “much of the river must flow as naturally as possible, keeping the impact on the environment to an absolute zero.” Instead of one Grand Inga Dam, they proposed “storage for those times when the river flow is much higher than normal constant flow” and “develop[ing] the concept of Grand Inga Cascades.” Grand Inga Cascades would use the same water several times before returning it to the river. Chief Engineer and CEO of Westcor, Pat Naidoo, asserted that “with sound engineering, much more output can be extracted with no impact on the environment.”  

Unrecognized and therefore undiscussed are the unique and important linkages between the Congo River and the equatorial Atlantic Ocean, and their relationships to global carbon and water cycles. The Congo River influences both surface and the deep-sea waters more than 700 km from its mouth. Design drafts of the new Grand Inga project have not been published, so the extent of river disruption is impossible to gauge. But any disruption of flow will certainly have consequences far out to sea, and perhaps, of global importance.
Relations between the Congo and its very large estuary (145 km long, 10 km wide at its mouth) conform to textbook descriptions of river function and conventional arguments against dams. Proponents countered that the absence of large human populations, a delta, and distinct seasonal flow regimes – as well as a run-of-river design – removed most concerns. Overlooked is the fact that the Congo actually has a very active delta – it is simply submerged far out to sea. An enormous submarine canyon beginning 30 km upstream in the estuary continues 730 km into the Atlantic Ocean, ending in a 300,000 km2 fan on the deep ocean floor. Varying from 3 km width and 400 m depth near the river’s mouth to 15 km wide and 1,300 m depth at the continental shelf break, the Congo Canyon descends to approximately 5,000 m. The fan has channels that have been traced for 900 km.

This enormous, complex and little-understood geomorphic feature is unique in that it provides a direct – and active – link between terrestrial ecosystems and the deep sea as solid organic material is transferred from the river and estuary out through the canyon towards the delta. Effects of the river’s substantial sediment loads have long been noted. Shipping lanes have required constant dredging, and the turbines of existing Inga I and II dams have been damaged by it. In 2001, research equipment at a depth of 4,000 m collected samples showing massive transmission of sediments and organic matter in a “cloud of particles” for several days, distributed over 13 km2 of ocean floor outside the canyon. The event demonstrated that “terrestrial carbon in turbid underflows cannot be neglected in the carbon budget of the whole Congo-Angola margin.” The source of this essential carbon is the Congo River and its estuary. Biological activity associated with “abundant tree leaves and rich fauna” was noted in a trawl 150 miles off the cost at a depth of 2,200 fathoms, and anomalies in the deep ocean thought to signify biological activity have been measured over an unexpectedly large area.

On the surface, Congo River water extends into the Atlantic Ocean in an ever-widening plume that has been measured seasonally 800 km offshore. Its biological activity is clearly visible in satellite imagery. Phytoplankton growth – and death – is central to global carbon balances. Carbon sequestration occurs when phytoplankton die and sink to the ocean floor, where they remain undisturbed. The function of the equatorial Atlantic is crucial in all calculations of global carbon budgets and, thus, climate function and change. Since the plume of the world’s largest river, the Amazon, which also empties into the equatorial Atlantic, is pushed northward into the Caribbean Sea by ocean currents, the significance of the Congo plume should not be underestimated.

In the context of growing awareness of the importance of the Congo for large-scale surface and deep Atlantic Ocean processes, plans to divert, store or otherwise intervene in Lower Congo River dynamics are truly alarming. Engineers and dam opponents agree that, whether mega or not, structures in rivers trap suspended material and release “sediment-starved water.” Reducing the Congo’s sediment will decrease its estuary and the river plume’s phosphorus and iron contents, as well as some organic matter. Could lower levels of phosphorus and iron affect biological production of the Congo plume? Could this affect the ability of the Atlantic Ocean to be a carbon sink?
The Congo River water deprived of its descent over rapids will be an oxygen-poor river, and a river deprived of its “higher than normal constant flow” would have a reduced plume with a reduced, rather then enriched, oxygen content. What would the associated loss of oxygen mean for estuary and ocean biogeochemical processes? Could oxygen deprivation reduce productivity or create a “dead zone” – in which waters are so depleted of oxygen that they can no longer support marine life?
Finally, how would any proposed reduction or alteration of the Congo’s flow – such as storing “higher than normal constant flow” – affect the transmission of terrestrial sediments to the deep ocean? Could the mechanisms of transporting turbidity events in the submarine canyon be affected in any way by changes in the Congo River’s properties or flow regime? These questions must be answered.

Beyond Mega

The twentieth century saw a rapid rise in technology’s ability to affect larger areas over longer distances, as well as the number of bio-geochemical systems simultaneously. With each increase in dimension came an increase in complexity in terms of interactions between human beings and the environment. In popular parlance, mega was a term that expressed the idea of larger-than-large, larger than local, a size almost beyond human ability to imagine. In 1939, the American Hoover Dam on the Colorado River was the world’s largest, creating a 640km2 km2 reservoir behind its 221 m high wall. At that time the dictionary definition of mega was one million times greater than expected was almost unimaginably enormous; ten times the size of large seemed a more manageable definition. No one had flown to the moon. The 1959 closure of Kariba Dam created the largest man-made lake in the world, with a surface area of 5,200 km2, and volume of 188,000 million m3. Mega was a mid-century term to describe a scale larger than normal, larger than large, larger than local.

This meaning quickly proved inadequate on the African continent, where dams proliferated, ever-larger structures were built, and reservoirs exceeded 100 times mega. To follow mathematical logics, it might be appropriate to introduce the term “giga,” which means101099, or 1000 million in American English, when discussing reservoirs. This is already used for the vast increase in electricity generation capacities that exceed the convention of megawatts (MW). A gigawatt is 1,000 megawatts, so Grand Inga’s estimated 39,000 MW reduces to a more manageable 39 GW. What would constitute a giga-reservoir? A thousand times a mega defined by volume? Length? Surface area?
Introducing the idea of a “giga” dam – or any other term to describe increases in physicality – neatly avoids the question of significance. What is the true meaning of these size increases, beyond the excitement of engineering achievements? With each increased dimension, more systems are disrupted, if not obliterated. Interconnected biological, hydrological, geological, and chemical systems and cycles interact locally, regionally and even globally, creating a planet conducive to human life. As human capacity to intervene has increased spatially and temporally, humans have separated themselves from other organisms that manipulate and co-create the environment in which they live. Humans have gained the ability to obliterate entire ecosystems over very large expanses, and to set in motion sequences of events with very longterm consequences, and in distant locations – seemingly without noticing, and certainly without accepting responsibility. What phrase can be used to describe such interventions?
And how can they be analyzed? In mid-twentieth century simplicity, the idea of an environmental impact assessment of a landscape intervention seemed a radical challenge to technological prowess. Battles were fought to save or protect species, and from this the idea of environmental conservation was reduced to a series of checklists. Once the list of endangered species was agreed upon, all that remained was to protect them – or a shred of habitat for a minimal population’s survival. The idea of protecting entire ecosystems and ecosystem function receded until reclaimed by environmental economists’ ideas of valuing identified “environmental services” – and protecting them. Once again, the environment was reduced to a checklist.

The hollowness of the list approach is frighteningly evident when larger-than-mega projects are considered. Clearly the world’s second largest river by flow is not only deeply involved with the function of its terrestrial drainage basin (watershed), but less obviously fundamentally important to the Atlantic Ocean into which it empties. What name could be given to a project that requires an impact analysis ranging from terrestrial flora and fauna (including humans) to the deep ocean floor and the global carbon cycle? Who could carry out such an investigation, and who would be able to read and comprehend such a report? Do we dare ignore the linkages because they are too complex and difficult to understand? The scale of possible consequences suggests that we cannot. Argument has been made in the past that sacrificing a local ecosystem could be justified for some “greater good” defined by an economic analysis. But how can one make such an argument when what is potentially sacrificed are elements vital to the balancing of planetary systems?
Grand Inga is far beyond the scale of a mega project. It exists in a realm of human escapism, in which technology allows postponement of accepting – and addressing – consequences of lifeways and logics of economics, the ultimate social construction. Perhaps it could be said that it resides in the “hubrisphere” and belongs to the category of “hubris” projects, those which require far more than local funding, materials and expertise for implementation and which have consequences that are extensive in space and time, and particularly those affecting boundaries between, or interactions among, atmospheric, aquatic and terrestrial systems and spaces. Hubris projects already exist; Grand Inga shows that there are no limits to our ever-more-hubristic engineering imagination.

Kate Showers is a Senior Research Fellow at the Centre for World Environmental History and Department of Geography, University of Sussex in the UK.

More information: 

This article is derived from a chapter in: Stanley D. Brunn (Ed.) 2011.  Engineering Earth: The Impacts of Megaengineering Projects.  Dordrecht, the Netherlands: Springer.    The book includes 126 chapters on a wide variety of megaprojects, including dams, industrial and transportation schemes, tourism, cities, construction companies and socially engineered landscapes.