Ron Canter's latest, a review of disastrous dam projects around the world, and examples of rivers, such as the Usumacinta, that are still free-flowing. I'll publish it in its entirety here (click More to see the whole essay) and the document can be downloaded here.
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BIG RIVERS, BAD DAMS Ron Canter, 3-26-07

Some of the most disastrous big dams around the world have been built in the tropics. The combination of high temperatures, impoverished populations, and water-borne parasites has been lethal. In North America Hetch-Hetchy and Glen Canyon Dams, while terrible in their own way, aren’t even in the same league with these.

Kariba Dam, Zambezi River

“The name Kariba [Kariva - “trap”] referred to a rock which thrust out of the swirling water at the entrance to the gorge close to the dam wall site, now buried more than a hundred feet below the water surface. In many legends, this rock was regarded as the home of the great river god Nyaminyami, who caused anyone who ventured near to be sucked down forever into the depths of the river.
When the valley people heard they were to be moved from their tribal lands and the great Zambezi River blocked, they believed it would anger the river god so much that he would cause the water to boil and destroy the white man’s bridge with floods.
In 1957, a year into the building of the dam, the river rose to flood level, pumping through the gorge with immense power, destroying some equipment and the access roads.
The odds against another flood occurring the following year were about a thousand to one - but flood it did - three metres higher than the previous year. This time destroying the access bridge, the cofferdam and parts of the main wall. Nyaminyami had made good his threat. He had recaptured the gorge. His waters passed over the wreckage of his enemies at more than sixteen million litres a second, a flood which, it had been calculated, would only happen once in ten thousand years.”– http://www.zambiatourism.com/travel/places/kariba.htm

Kariba Lake – length 280 km at max pool

In 1960 the gates closed on Kariba Dam at Chirundu and 280 km of the Zambesi slowly became a stillwater lake, the largest artificial lake in the world at the time. “Kariba” means “trap”, which it was for wildlife that crowded onto shrinking islands and then drowned as the lake overtopped them. Operation Noah, an international rescue effort, saved over 7000 animals from drowning, but was overall not very successful. Many more drowned, the cost was great, and the survivors’ habitat was gone anyway. Needless to say, the cost of the wildlife rescue had not been factored into the planned cost of the dam.
At Zambezi Deka, where a road reaches the river, the Zambezi has become a long thin lake set deep in the Batoka Highlands. Soon the gorge begins to widen into a narrow valley. Eutrophication has favored masses of aquatic vegetation in the stillwater. Visible in satellite images are bright green floating mats of vegetation caught in coves and between islands – they even block the main channel in one place. Below the road from Msuna, the stilled river enters another gorge, which it threads quietly for 19 km.
The river widens and runs northeast for the next 20 km. The river/lake turns left through a rock gate and expands in Gwembe Valley, once home to thousands of farmers and hordes of wildlife. For 150 km the lake is a man-made inland sea 25 to 30 km wide - about half as wide as Lake Erie. At Upper Kariba, 96 km before the dam, there were once heavy rapids in a short canyon. Now the lake just narrows briefly to 5 km wide.

Manantali Dam, Bafing River, one of the Senegal River’s two main sources

The Bafing River in Mali is one of the two main sources of the Senegal River. Completed in 1987, Manantali Dam – a “poster child for bad dams” – plugs the river about 800 km above its junction with the Senegal. In 2001, 14 years after it was built, Manantali Dam finally began producing electricity. 55% of the power generated goes to Mali, 45% to Senegal. Water-borne diseases (malaria, urinary diarrhoea, intestinal parasitic diseases, schistosomiasis, and intestinal schistosomiasis, a much more dangerous form of the disease) have spread rapidly via still water and irrigation canals. There has been a massive disruption of ecosystems downstream in Senegal and Mauritania. Manantali was so clearly a boondoggle that the World Bank took a pass on this one and would not fund it.
Irrigation agriculture has actually turned out to be less productive than the flood-recession farming it displaced all along the Senegal River for 800-900 km downstream. The high cost of building a system of irrigation canals has resulted in only a fraction of those planned actually being completed. In every irrigation plan, the government has favored large farms, and small farms have been shut out. Worse, poor farmers no longer able to plant flood-recession farms have had their lands appropriated. In addition, the river is becoming undrinkable due to the return flow being polluted by chemicals used on irrigated fields.
One intention was to make the Senegal River navigable year-round but that has not worked well so far. The dam does not normally impound enough water to meet all its touted goals: irrigation, hydropower, and navigation. The dam may actually be contributing to desertification in Mauritania, along the north shore of the Senegal River by changing annual evaporation patterns.

Diama Dam, Senegal River
From Bakel to St. Louis the Senegal River winds across a broad flood plain, the ‘delta’ of the Senegal River. It is flat and easy traveling, when there is water enough. The first half is seasonal; the second was tidal before the Diama Dam was built.
Before damming, tides reportedly affected the river as far as 400 km from the ocean. In 1986 the Diama Dam was built 27 km upstream from St. Louis in an attempt to stop the intrusion of saltwater, which in turn was being aggravated by the disruption of normal freshwater flow by the nearly complete Manantali Dam over 900 km upstream. The Diama Dam also diverts water south into the bed of the Ferlo River to store for the dry season.
The dam has caused eutrophication and disease in the delta by encouraging a dense growth of aquatic nuisance plants (mainly Typha australis), which clog the waterways and harbor vectors of water-borne diseases. An explosion of mosquito and snail populations has brought malaria and both urinary and intestinal bilharzia to epidemic proportions.

Kanji [Kainji] Dam, Niger River
Started in 1964 and completed in 1968, Nigeria is still paying off the debt on it (as of 2006). Instead of plugging a narrow gap like most dams, it snakes across a broad valley. At 9 km, it is one of the longest big dams in the world. It backs up a lake about 160 km long. The widest part is not behind the dam but halfway up, where the lake opens into a huge oval bay 48 km long and 24 km across.

Cahora Bassa Dam, Zambezi River

Quebrabassa Gorge, the final canyon on the Zambezi, begins below Zumbo, where the river slides into Mozambique, considered the poorest country in the world. The 1911 Encyclopedia gave the length from the first to the last of the rapids as 70 km, and indicated that the portage road was longer, “taking a detour of 70 miles (112 km)”.
The river is dammed halfway down the canyon to form 250 km long and 26 m deep Cahora Bassa Lake. The 170 m high dam was completed in 1974. The lake pinches through three narrows, vestiges of major cataracts at hard rock layers. The lake is very windy. Built for contradictory functions: flood control and power generation, the dam’s resulting flow regime has been very erratic. Since there is little demand for electricity in Mozambique, electricity is sold at cut-rate prices to South Africa. Even villages near the dam remain without power because the cost of building the grid is beyond Mozambique’s limited resources.
In common with the Kariba project, Cahora Bassa displaced tens of thousands of people, hordes of wildlife, and permanently flooded productive farmland. In addition, it has had a huge impact for 500 km downstream in the floodplain and coastal delta. Without annual overflow to floodplain pools, the fish have not been able to spawn in the huge numbers that once supported villages. Flood-recession farms along riverbanks are periodically washed away by unexpected dry season releases. Big game hunting, a significant source of regional income, has withered as the game animals have suffered from reduced wetland productivity. Nearing the coast, the mangroves are dying back without the silt renewed at their roots. Mangroves both protect the coast and are a habitat for prawns. In addition, the river channel is now often too shallow for navigation in the dry season above Tete. The net result has been to deepen the poverty of the average person living along the river.

Proposed Mphanda Nkuwa Dam, Zambezi River

The unflooded portion of Quebrabassa Gorge appears to have six major rapids, at least for now. Pictures of the gorge show high volume rapids in a spectacular canyon. Forested walls curve upward to cliffs topped by bare rock knobs.
“The Mozambican government is proposing to build the Mphanda Nkuwa Dam [Mepanda Uncua] 60km downstream from the Cahora Bassa Dam. It is estimated that the dam would produce as much as 1,300MW of electricity that the government anticipates using to attract energy intensive industries to Mozambique, including expansion of the Mozal Aluminum Smelter, but this power would come at a high price. The proposed dam is already a priority infrastructure project under the New Partnership for African Development (NEPAD), which is promoting Mphanda Nkuwa for increased supply of the regional electricity grid, primarily for industrial supply.
In addition to displacing 1,400 rural farmers, the Mphanda Nkuwa Dam would require the Cahora Bassa Dam to operate according to its current destructive release patterns, and make downstream restoration very difficult to achieve. Mphanda Nkuwa could also exacerbate downstream social and environmental damage by causing daily fluctuations in river level. These mini–floods are predicted to flood ecologically important sandbars and riverbank food gardens which provide the only vegetable resource for many local farmers and are essential for ensuring food security during the dry season. The water fluctuations will also impair fishing and navigation by canoe, especially in the stretch bewteen Mphanda Nkuwa and the city of Tete. The $2 billion project also poses significant economic risk to Mozambique, one of the world’s poorest nations.” - http://www.irn.org/programs/mphanda/

Volta [Akosombo] Dam, Volta River
The stillwater lake has caused the spread of tripanosomiasis, “river blindness” like wildfire. Between 1960 and 1964 the rate in children rose from only 5% to 90%. It now afflicts virtually everyone living near the river, and half of those over 40 have gone blind.

Aswan High Dam, Nile River
The 110 m high dam supplies much of Egypt’s power, greatly increased the area of farmland, ended the annual floods, and allows two to three crops annually, but is not without long-term trade-offs.
Starting in 1967, Lake Nasser began to fill. By 1971 it had drowned 1000 known archaeological sites, the majority of which were never even surface surveyed due to lack of time and resources. Nearly 50,000 people were displaced. Effects included ending the flow of nutrients to riverside fields downriver and the intrusion of saltwater up delta distributaries now too feeble to resist.
The breadbasket of the Mediterranean, Egypt sustained intensive agriculture for a staggering 5000 years. Throughout its history, the nation practiced “flood recession farming” on a grand scale. Every year (with unpleasant exceptions) the Blue Nile rose on schedule and flushed rich Ethiopian silt from the highlands into the Nile itself. As is well known, the rise of the river spread the muck over fields in Nubia and Egypt all the way to the Mediterranean, watering them and endlessly renewing their fertility with “the magic mud that can raise cities from the desert sand” (Churchill, 1902). To quote an unnamed ancient poet, “The fields laugh and the river-banks are overflowed. The visage of men is bright, and the heart of the gods rejoiceth”.
All that has ended with the construction of the Aswan High Dam and two others in Nubia on the Blue Nile. No one needs to leave the bottomland to escape flooding but Egyptian farming methods have completely changed. Now Egyptian farmers need to buy water to irrigate their fields and fertilizer to maintain fertility. Whether they will be more prosperous in the long run remains to be seen. Hopes for the dam to be a “wall against hunger” have not been realized. The birth rate has simply kept pace with the increased harvest. Given the population crowded along the shores now, it would be impossible to revert to the ancient high and low Nile cycle.
Archaeologically the Aswan High Dam was the single worst thing to happen to Egyptian and Meroean antiquities ever. A few high profile sites were dismantled and rebuilt on higher ground, or protected by dikes at great expense. The 1,000 other sites identified in the salvage survey all went under - 4000 years of history gone (Keating, 1975). Most sobering was that, when the archaeological surveys began, less than 100 sites were known. In spite of the massive UNESCO salvage effort, only a fraction of the sites discovered could be systematically excavated.
Huge forts of mud-brick guarding the portages, their landings, a ship portage road, and a system of wing dams making the river navigable were all discovered, minimally excavated, and then lost forever. Buhen, the greatest of all the forts, was preserved for 4000 years by the desert and neglect. With its multiple dry moats, flaking fields of fire, drawbridges, archer slits, etc, it was the most sophisticated defensive structure in the world until the Venetians finally surpassed it. Now it can only be toured virtually- the original has dissolved into a pile of mud.

Merowe Dam, Nile River
In Sudan, construction began in 2006 on the Merowe [Hamdab] Dam at Hamdab 31 km above Marawi [New Merowe]. It will flood the Fourth Cataract of the Nile and more – 160 km upriver in all. It is officially multipurpose but hydropower is the main goal. Planned to be 67 m high and 9 km long, it is the largest hydro project in Africa currently under construction (Cost: 1200 million EURs, or 1.5 billion dollars). The dam is 9 km long because the river is not in any sort of gorge here, just a broad valley with isolated hills, two of which are being dismantled for fill. The 10 hydro generators, ranked across the right-hand channel around an island at Hamdab, are nearly complete. The principal contractor is the China International Water & Electric Corp. “The creation of the reservoir lake will increase the surface area of the Nile by about 700 km_. Under the climatic conditions at the site, additional evaporation losses of up to 1,500,000,000 m_ per year can be expected. This corresponds to about 8% of the total amount of water allocated to Sudan in the Nile Waters Treaty” (Wikipedia, 2006). There have been no environmental assessments – not one.
Since the only arable land is in narrow strips fronting the river and in patches on islands within the cataract, the 50,000 people who will be displaced have nowhere to go. Beyond the narrow river bottom all is desert. The plan is to relocate them to dry farms, where they will have two years of irrigation free, and then have to buy water. The desert soil is poor and may take 40 years of nurturing to bring it up to the level of the farms lost. Basically, the displaced Manoosir farmers are being shoved into the desert to wither and die – and they know it. The Sudanese displaced by the Aswan Dam were relocated along a miserable stretch of the Atabara River, and languish there still. Several Manoosir protesters were killed by Sudanese police in April 2006. The plight of 50,000 Manoosir is lost in the larger tragedies of modern Sudan - like the hundreds of thousands killed in Darfur.
Flooding starts in Aug 2007 and may take two years to reach max pool. There are half a dozen salvage archaeology expeditions underway (Archaeology, Nov-Dec 2006, Andrew Lawler, on the Humboldt Univ. Nubian Expedition), but all are small and often met with hostility. The Manoosir don’t want any outsiders - archaeologists included -in their territory along the Fourth Cataract. In spite of this, hundreds of sites have been located, but there is no time or resources to do much with them. “The Fourth Cataract--after a brief emergence into the archaeological limelight--seems destined to slip back into obscurity, this time for eternity” (Lawler, 2006).

Rusayris Dam and Senna Dam, Blue Nile
Within Sudan, the Blue Nile is dammed in two places: Rusayris [Roseires] Dam at Damazine (1950s), and Senna Dam (1925). The river’s huge silt load has already filled both reservoirs and converted them into black, oozing mudflats. In the past that muck would have ended up on Sudanese and Egyptian fields, restoring their fertility. Now it just bakes in the sun.
The Great Gezira Plan to grow cotton with irrigation from Senna Dam long ago evaporated, but twin irrigation canals run north from the left side of the Senna Dam (3 km long, about 20 m high). They water small farms in a region stretching 200 km from the dam north to Khartoum. Along the river itself are the prodigious ruins of British pumping stations, “a museum of broken schemes” (Bangs 2005).
The interconnectedness of all things has nowhere been more glaringly obvious than along the Nile from source to sea. The broad outline of it has been known from ancient times, yet the nations along it - Egypt, Sudan, and Ethiopia – all dam and divert it without careful thought to consequences.

Diamer-Bhasha Dam, Indus [Sindhu] River
Located where the Hindu Kush and Himalaya Ranges come together, the Diamer-Bhasha Dam will destroy one of the world’s largest collections of rock art, carved on boulders along the upper Indus and ranging in age from Neolithic to 16th cen. Approx 50,000 carvings and 5,000 inscriptions are being documented by a German team, but the boulders are too big to be moved. They will either be inundated by Bhasha Lake or destroyed in reconstruction of 100 km of the Karakoram Highway. http://www.dawn.com/2006/12/05/nat11.htm
A groundbreaking ceremony was held in May of 2006, work on the infrastructure has begun, and construction of the dam itself is slated to begin in 2008. 30,000 people from 32 villages (including ancient Chilas) will be displaced. The dam will be about 165 km downstream of Gilgit and produce 3.36 megawatts. Water storage in perennially dry Pakistan is another major purpose, but hydro-power and water storage are not mutually supportive uses. At a cost of $6.5 billion US, the dam is intended to be the flagship of efforts to develop Pakistan’s Northern Areas. A concern of opponents is that the dam will increase local humidity, leading to more rapid melting of glaciers in the mountains nearby.

and of course, the biggest dam boondoggle of all, flooding entire canyons to their brim:

Three Gorges Dam, Ch’ang Chian (Yangtze) River
All the problems of big dams, but writ even larger, afflict the Three Gorges Dam in China, for it is the mother of all dams – the world’s largest hydro and flood control project. The stats are mind-boggling. The dam wall will be 185 meters high; the normal pool 174 meters deep. Xiling Gorge, the last of the historic and scenic Three Gorges, will be flooded nearly to its brim. One could drop the Great Pyramid into the pool behind the dam – and it would sink out of sight. 1,250,000 people, 13 cities, 140 towns, and 1352 villages are being removed to make way for the lake. By the time it is done in 2012, it will be the most expensive construction project in history. The hydros will generate 17 to 18 gigawatts (at $2000 per kilowatt). The lake will stretch upstream for 600 km, past the city of Chongqin, which will become a port for ocean-going ships. The Aswan High Dam flooded 1000 archaeological sites. The Three Gorges Dam will swallow 8000, some 10,000 years old (Winchester, 1996).
The dam will accomplish its four main goals: flood control, power generation, improved navigation, and reduction of sulphur and CO2 emissions by reducing need for coal-fired plants. The key question though is “For how long?” The Achilles heel of the Three Gorges Dam is the smallest of things – silt. The river carries an enormous silt load, 530 million tons annually, which the lake will intercept. Chongqin may become a port of ocean-going ships for a time, but there is little doubt that the silt deposited in the upper end of the reservoir will quickly fill the channel. Bed load ranging from silt to boulders will also accumulate behind the dam, and constantly threaten to clog the turbine intakes.
More serious is the effect of relieving the lower river of its silt. With a dramatically reduced sediment load, the swift Ch’ang Chian will actively erode its banks and levees downstream of the dam. Since Shanghai, China’s largest city, is built on river mud, erosion may threaten the long-term stability of its foundations. The river delta will stop growing seaward, and probably retreat. Salt water and tides will certainly move farther upriver. Shanghai (which means “Above the Sea”) is over1600 km downstream of the dam, yet the dam will affect it.
Other negative consequences include massive environmental damage, enormous relocation problems, possibly creating an underclass of “dam refugees”, increased risk of landslides, and the destruction of some of China’s finest and most iconic scenery - the Sanxia: Qutang, Wu, and Xiling Gorges.
Finally, there is the question of the long-term safety of the dam itself. It would be a prime site for terrorist attack. The site finally chosen at Sandouping has serious shortcomings for air defense (Winchester, 1996). A major landslip (such as the collapse of the Huangla Stone, an overhanging cliff 40 km upstream) into the lake could send a wave surging over the dam. In August 1975 a typhoon overwhelmed the much smaller Banqiao Dam on a tributary. “The vast structure promptly burst: the resulting lake stretched for thirty miles downstream, and whole villages were inundated in seconds. Almost a quarter of a million people died. News seeped out only in 1994, nearly twenty years after the event” (Winchester, 1996). If the Three Gorges Dam burst, millions would die.
Dai Qing, a Beijing journalist, gathered up all the papers of respected engineers and hydrologists and published them in 1989 in a book. Within two months she was in prison, but the information sparked an unprecedented vote by the National People’s Congress in 1992. They were to rubber-stamp the Three Gorges project, but, when debate was forbidden, one third voted against or abstained anyway. After the vote, all international support was withdrawn, particularly funding from the banking community. China was left to go it alone.
“A general feeling had arisen that large dams were ill-conceived projects, that few of them had realized the expectations offered for them, that all were too costly, most had caused grave environmental impacts on their surroundings, and that each was little more than pomposity writ in concrete, with totalitarian regimes favoring them most notably as a way of impressing the peasantry with the ruler’s acumen, energy, and skill.” (Winchester, 1996, pgs 227-28)

In General:

In most cases the effects of flooding the land upstream of the dam were recognized during planning. They were sometimes understated - often intentionally - but the loss of farmland and the displacement of thousands of people never came as a total surprise.
What is disturbing is how often the effects downstream of the dam were not anticipated at all. The only result usually touted is that annual flooding would now be controlled. This is seen as a good thing, until the full effects are realized. Profoundly altering a river’s annual cycle affects every living thing downstream - from man to bug - that has adapted over time to live within that cycle.
In every case, changing the annual flow regime on a big river has had a tremendous negative impact on floodplain farms, disease vectors, wildlife habitats, and offshore fisheries for hundreds, even thousands, of kilometers below the dam. Even when the likely results are pointed out, the tendency of planners has been to minimize or ignore downstream impact, possibly because it is not so easy to quantify as acreage flooded or people relocated. In addition, there is a clear pattern: the bigger the river, the worse the downstream consequences.
The loss of archaeological sites is a given. Past people chose to live by the river for good reasons: drinking water, fertile farmland, and a natural road. A rule of thumb from past salvage projects seems to be that, whatever the number of known sites at the start, the number found by the end will be at least ten times larger.
Once a dam is built, the people are stuck with the results, like it or not. The dam will never be dismantled. It would be too costly, and an admission of failure. In spite of the catastrophic results from those already in place, more are even now being built.

BIG RIVERS, NO DAMS

There are several world-class rivers that have not got their big dam yet, thankfully for very practical reasons. Instead, they have run-of-the-river hydros, which have little impact on the basin above or below.

Mekong River

Presently the Mekong River in Southeast Asia follows its annual rhythm of dry and monsoon levels as it always has. Where the ragged crest of Phu Khan He Mountain rises above the right shore, a band of resistant rock crosses the river. Starting at an elevation of 74 m, the Mekong drops 21 m in only a few km just before crossing from Laos into Cambodia. The length of the falls is usually given as between 10 and 12 km, but this is actually their width – they span 11 km.
Khone Falls is one of the widest waterfalls on any river in the world. Since the river is not confined in a gorge, the falls spread wide among parallel channels, five or six in the dry season and a dozen in the monsoon. Wherever joints have created a weak zone, there the river has etched a channel. Each channel has its own set of falls, and none are navigable. For whitewater paddlers, it is the classic “carry up and run another chute” scenario – on steroids. Endangered Irrawaddy dolphins hang out below the falls and are a local tourist attraction.
Khon Pha Pheng Falls, in the easternmost channel below Thakho, is the largest of the falls because it is the most abrupt drop, taking most of the 21 meters at once. Somphamit Falls, in a channel along the south side of Don Det (“don” means island), are somewhat smaller, since they are preceded by rapids. Other rapids and falls are in narrow channels between Don Phapheng, Don Sadam, and Don Sahong. West of Somphamit in a seasonal channel are the falls of Nam Keng, though at the height of the monsoon most of the low islands west of Don Det and Don Saniat are underwater.
The remains of a French railway, built to ease a portage past the falls, are still traceable. Built on Don Khone, a large midriver island, it ran only 5 km from the head of rapids above Nam Somphamit to Hangkhon village, at the foot of a hill where most of the channels rejoin. It probably just improved an existing portage trail.
There is no narrow mountain gap to plug. A dam would have to be over 12 km long to block all the channels and that is almost too much for even the most ardent dam builder to suggest with a straight face.
The Tad Somphamit Hydro produces power by diverting a small part of the average river flow (10,663 m3/s) for 2 km through a tunnel. It dewaters a short stretch of one channel at the height of the dry season but does nothing more. Though the river volume is less, the hydro’s output is highest in the dry season. In the monsoon, the tailwater level rises, reducing the drop. In the planning stages, Thakho Hydro would tap Khon Pha Pheng Falls with a one km tunnel to its own run-of-the-river plant.
Run-of-the-river plants may have local effects but they have no impact on the annual wet-dry cycles of a river basin. But this could change for the Mekong. A high dam in a Laotian mountain gap 24 km above Vianchang (and 2000 km from the sea) has been proposed. By ending the Monsoon high water, it would prevent floods in Laos. It would also compromise the renewal of the fertility of Lake Tonle Sap and of the Mekong Delta, breadbaskets of Cambodia and southern Vietnam. this would incidentally disrupt the fisheries of all of Southeast Asia, since Lake Tonle Sap’s annual backfilling in the monsoon is essential for the spawning cycle of all commercial species. It sounds like a cliché, but the whole Mekong watershed really is one huge interlocking ecosystem.

Congo River

In the second set of rapids forming Livingstone Falls on the Congo a short swift stretch leads into a particularly long series of continuous rapids, the Inga Rapids. The river falls 96 m in 14 km for an overall gradient of 6.9 m/km (35 ft/mi) – an incredible descent for the second largest river on earth. In the world list of waterfalls by volume Inga is number one.
Inga Rapids tumble southeast in a wide channel to Sikila Island, only to suddenly double back to the southwest and squeeze into a narrow gorge. There are no pools or breaks, but there are five major drops within the Inga Rapids: two above the corner, a wide one right on it, and two below. The last drop is particularly huge, possibly the largest rapid on earth. The Congo’s flow at Inga is 43,000 cubic m per sec (1.5 mil cfs) and it has not escaped the attention of hydro planners.
In the late 1970-early 1980s, the Inga Power Project built a diversion canal above the left shore, with one power plant [Inga Power 1] part way down, and a second [Inga Power 2] where the river doubles back. Since the Congo’s flow is fairly constant, there is no need for a dam. Rather, they are run-of-the-river hydros. Both are running at only half capacity due to poor maintenance, which was in turn due to the Congo civil war. At full capacity their output is greater than all of Italy’s power plants combined – all this with no dam. There are plans to upgrade them and add a third plant, if money can be found. All are in the Nkololo Valley.
The Grand Inga scheme goes far beyond merely adding to existing hydros. The paln is to dam the Congo and divert the entire river through the Bundi Valley. The cost of actually plugging the second largest river in the world by volume would be astronomical. In fact, it would cost a minimum of $50 billion. Planned to generate 39,000 MW, it could fill the current power demands of most of the African continent by itself, but only select regions would be tied in to the projected Pan-African grid. It is not clear where the money would come from.
Unlike the current run-of-the-river hydros, Grand Inga would disrupt the Congo’s flow and massively impact the regional ecosystems. It would also be a prime target for saboteurs. Given the enormous price tag and the poverty of the Congo, it would seem unlikely that it could ever funded, but stranger schemes have been pushed through to completion – with terrible consequences for the poor countries so favored.

and the Usumacinta River is undammed - so far.

Citations:

Bangs, Richard & Pasquale Scaturro
2005 Mystery of the Nile. New American Library, Penguin Books, London, UK

Churchill, Winston
1902 The River War, in Gutenberg E-text
1903
Forbath, Peter
1977 The Congo. Harper & Rowe

Keating, Rex
1975 Nubian Rescue. Hawthorn Books, Inc. New York, NY.

Lawler, Andrew
2006 “Damming Sudan”, Archaeology, Nov-Dec 2006. On the Merowe Dam and Humboldt Univ. Nubian Expedition

Alan Moorehead
1960 The White Nile
1962 The Blue Nile. Hamish Hamilton, London

Winchester, Simon
1996 The River at the Center of the World. Henry Holt, NY

http://www.nadir.org/nadir/initiativ/agp/free/dams/index.htm
Problematic big dam projects worldwide

http://www.learningsites.com/EarlyWork/buhen-2.htm
Buhen Fortress

http://www.utdallas.edu/geosciences/remsens/Nile/Cataract-Semna.html
Semna site on Nile in Sudan, now drowned

http://www.zambiatourism.com/travel/places/kariba.htm
Kariba Dam

http://www.irn.org/programs/mphanda/
Mphanda Nkuwa Dam

http://www.dawn.com/2006/12/05/nat11.htm
Diamer-Bhasha Dam

http://american.edu/ted/threedam.htm
TED case study, 3 Gorges Dam

http://www.visit-laos.com/where/champassak/outandabout.htm
Sii Pan Don and Khone Falls

http://etext.library.adelaide.edu.au/b/burton/richard/b97g/chapter26.html
Two Trips to Gorilla Land and the Cataracts of the Congo, Richard Burton, with map of lower Congo

http://www.irn.org/programs/congo/index.php?id=050907illusions_eng.html
Grand Inga Power Project