Analysis: A dam(n) crazy idea
Right now there are 10,000 cubic kilometres of water behind dam walls – five times the volume in the planet’s rivers. The weight is so great it triggers earthquakes, and geophysicists estimate that the redistribution of weight from reservoirs may be having a measurable impact on the speed the earth rotates, the tilt of its axis and the shape of the gravitational field. But there’s something the dammers haven’t been telling you: dams die. And when they do, all hell breaks loose. By DON PINNOCK.
We’re going to get their stinking dam. We’ve got secret plans. We’re going to set up a laser beam below the dam, drill a tiny hole through the base of it. We’ve got underground chemists working on a formula for a new type of acid that will dissolve concrete underwater. We have suicide freaks who want to grow up to be human torpedoes. We’ve employed a crack team of serious Christians who are praying around the clock for an Act of God. . . . – Edward Abbey, eco-activist
We’ve plugged the Tugela, the Orange, the Limpopo and the mighty Zambezi. There are dams on the Congo, the Niger and the Nile. The Mississippi has been halted, the Colorado no longer reaches the sea, the Ganges has been tamed and the Yangtze is a toothless dragon. Every major river in Europe is not only stoppered like a bathtub but turned on and off like a tap.
There are more than 40,000 large dams in the world and some 800,000 smaller ones. The mania to dam began in the 1950s and we’re now running out of rivers so we’re damming dams. Just think about it.
Right now there are 10,000 cubic kilometres of water behind dam walls – five times the volume in the planet’s rivers. The weight is so great it triggers earthquakes, and geophysicists estimate that the redistribution of weight from reservoirs may be having a measurable impact on the speed the earth rotates, the tilt of its axis and the shape of the gravitational field.
But there’s something the dammers haven’t been telling you: dams die. And when they do, all hell breaks loose. Many dams – especially the megadams – are some of the most dangerous, ecologically invasive, morally corrupt and politically questionable structures human beings have ever built. It’s time to start killing them.
You want to keep reading? Let’s start with dangerous. There are two main ways a dam can fail: ‘overtopping’ (responsible for around 40 per cent of failures and foundation problems (around 30 per cent).
In August 1975, a storm hit Henan province in China with a velocity estimated at a one-in-2,000-year event. The Banqiao Dam on a tributary of then lower Yangtze filled close to maximum, but when its sluice gates were opened it was found that they were partly blocked by sediment.
The dam kept rising. On 7 August it burst and 500 million cubic metres surged through the downstream valleys and plains at nearly 50 kilometres an hour. Entire towns disappeared. When the wall of water hit the Shimantan Dam, lower down, it was flattened, as were 60 other smaller dams down the river.
The floodwaters formed a lake covering a thousand square kilometres. It is estimated that 171,000 people died, with 11 million losing their homes, but the disaster was airbrushed out of history. Information about it leaked out only 20 years later.
In 1959 the Vaiont Dam – the world’s fourth highest – was completed at the base of Mount Toc in the Italian Alps and began filling. Soon afterwards seismic shocks were recorded and a mass of unstable debris began to slide towards the reservoir. It was partly drained and the shocks stopped.
Photo: Vaiont Dam (Wikimedia Commons)
When filling commenced the shocks returned, but engineers and geologists decided the slipping mass would keep moving slowly and filling continued.
After heavy rains on the night of 9 October 1963, 350 million cubic metres of rock broke off Mount Toc and plunged into the dam. A gargantuan wave – the height of a 28-storey building – overtopped the wall and within two minutes the town of Longarone, a kilometre downstream, was levelled, killing most of its inhabitants. About 2,000 people died.
Of dam disasters which killed more than 1,000 people, it has been estimated that 35,509 have died in the last 150 years. There have been many more smaller dam failures. Dams are no more unbreakable than the Titanic was unsinkable.
One of the least-publicised effects of mega-dam construction is their tendency to trigger earthquakes. In their book Vanishing Waters, biologists Bryan Davies and Jenny Day explain that this is caused by water weight, lubrication and the pattern of filling. The mass of water in a dam like Kariba weighs, they calculate, around 180 billion tonnes. Cahora Bassa clocks in at 63 billion.
Photo: Kariba Dam (Wikimedia Commons)
This enormous mass and the rate it accumulates during filling forces water into rock faults below the dam, lubricating them and forcing them to groan and writhe. It’s named reservoir-induced seismicity.
Photo: Cahora Bassa Dam (Wikimedia Commons)
As Kariba filled, it caused two quakes greater that six on the Richter scale. Ever since there have been rumours and hints of secret reports about structural damage to the dam’s foundations. If Kariba goes it will take Cahora Bassa with it. More than a million people will be in its floodpath. The towns of Tete and Quelimane would disappear. In a book named, poignantly, Silenced Rivers, Patrick McCully logged 32 dams hit by seismicity greater than four on the Richter scale.
If you want something to worry about, though, you need to go no further than the Katse Dam. This 187-metre monster (the tallest dam in Africa) is part of the six-dam Lesotho Highlands Water Scheme, one of the deepest and most sinuous such systems in the world. When the project was signed into existence in 1987 no environmental impact assessment had been done. By 1997 the first phase of the scheme (the main aim of which is to get water to Gauteng) had run to R9-billion. The Mohale Dam, completed in 2002, cost a further R7,2 billion.
Within 18 months of the Katse filling there had been 95 seismic events in its vicinity. In February 1996 a tremor ripped a 1,7-kilometre crack in a mountain and through a village just north of the dam wall. The dam is engineered to withstand a 6,5 quake, but Chris Hartnady of the University of Cape Town has suggested that a tremor as high as 7,1 could be on the cards because of the thinness of the Earth’s crust in that area.
If the Katse bursts when full, according to Davies and Day, the wall of water surging down the Malibamasto Valley will completely destroy Aliwal North several hundred kilometres away and still be five metres high by the time it reaches the Gariep Dam.
If geographers can make mistakes about dam siting and engineers can guess about necessary dam strengths, builders are no less fallible. Huge amounts of money are involved in dam construction and rackets abound. No less than 19 large, international contractors to the Katse project ended up in court on bribery charges. Evidently with the knowledge of the World Bank (which provides most of the funds to build dams worldwide), more than a million pounds sterling was handed to a Lesotho official in order to shoe-horn the dams contracts into place.
In such an environment of graft, the temptation to make profits by cutting corners, using inferior materials, using under-strength concrete or turning a blind eye to expensive processes is compelling. Worse. There is a growing consensus that the World Bank is using the leverage of vast sums of money to finance Third World dams in order to conduit funds to First World construction companies. The dams are incidental.
Two-bit politicians opening gigantic structures look good – not many will claim a dam isn’t in the public interest? And developing nations end up with massive foreign debts. Who says colonialism’s dead? And, as usual, dictatorial regimes are preferred in order to to curb the inevitable backlash from ruined peasants.
Dam failures, however, are only part of the problem with dams. The Three Gorges Dam in China have displaced around 1,3-million people. The Narmada water project in India has been dubbed India's greatest planned environmental disaster; it displaced 1.5 million people. Arundhati Roy, the environmental campaigner who wrote The God of Small Things, described big dams as weapons of mass destruction: “They are to a nation's ‘development’ what nuclear bombs are to its military arsenal.”
Photo: A file photo dated 25 May 2003 of a group of residents leaving Fengjie, a historic town in southwest China's Chongqing Municipality. The 2,300 - year - old city was the one of the first towns to be submerged by the Three Gorges Project on the Yangtze River in June 2003 by the Three Gorges Dam project. By mid - June, the dam have created a lake of 135 meters depth. EPA-PHOTO/QIU YAN
It is conservatively estimated that more than 65 million people worldwide, often from politically weak minorities, have been forcibly removed from their homes as a result of dam construction.
The damage dams do to the environment is incalculable. In Silenced Rivers, Patrick McCully describes each dam as “a huge, long-term and largely irreversible environmental experiment without a control.”
Above the wall huge areas are simply inundated, often drowning so much greenery that intolerable amounts of methane and other greenhouse gases are pumped into the atmosphere from rotting biomass.
Davies and Day estimated that a single dam – Manyame in Zimbabwe – drowned several hundred tonnes of termites alone, never mind the earthworms, spiders, lizards, bacteria, fungi, thorn trees, grasses, daisies and mopane trees.
Very often more fertile lands are lost under dams than are gained through irrigation schemes from dams. When the Dnieprostroi Dam was built in Russia, it inundated so much prime Ukranian farmland that Soviet hydrologists claimed burning hay harvested from the area it submerged could have yielded as much annual energy as was generated by the dam’s power plant.
Photo: Dnieprostroi Dam (Wikimedia commons)
Down river from dams, especially in Africa with its flood and drought cycles, the damage to ecosystems is disastrous. Floodplains – where rivers flow into the sea – are some of the world’s most diverse ecosystems.
Creatures great and small have evolved in synchrony with the flood cycles, nourished by the annual silt flows and dependent on the scouring effect of floods. Instead of flushing silt, the river simply deposits it in the dam. After not too long the water is more akin to thick lentil soup. Difficult stuff on which to run a turbine.
Hailed as the solution to annual flooding, dams are simply killing floodplains – and people in them. Flood ‘pulses’ are the main reason for the astonishing diversity and productivity of floodplains which have been calculated at being 65 times richer in life than the seas. The tropical coastal waters near floodplains produce fish yields a hundred times higher than where there are no floodplains. In recent times, because of dams, around 20 percent of the world’s freshwater fish have become extinct, threatened or endangered.
Not only fish are dying, however. For years Bryan Davies has been warning of a disaster in the making in the Zambezi floodplain. By taming the floods, the Cahora Bassa Dam encouraged peasant farmers to move into the floodplain and to further upriver towards the dam. When the huge floods hit in 2000 and again in 2001, Kariba engineers opened all their sluices to protect the dam but failed to inform their counterparts at Cahora Bassa. To prevent overtopping, Cahora Bassa suddenly opened all eight sluices, causing the wall to vibrate so violently on one occasion that engineers are reported to have fled the wall.
The resulting floods devastated the Mozambican floodplain, requiring a massive international rescue campaign and drowning hundreds of people. Today most of those who survived are still in vast refugee camps south of Caia, their livelihoods gone. A rivers ecologist has described the dam as “having the dubious distinction of being the least studied and possibly least environmentally acceptable major dam project in Africa.”
Unbelievably, Zimbabwe and Zambia are planning to build another dam on the Zambezi – which will inundate the Batoka Gorge below Victoria Falls with the highest dam wall in Africa. Mozambique (for political reasons: Portugal owns Cahora Bassa) is planning to throw a wall across the Zambezi below Cahora (and inundate the finest tiger fishing area in the world).
So are dams necessary? Of course: they provide water and power. But we don’t need them so huge, in such large numbers and, often, in the countries in which they’re built. They are neither cheap nor clean technology.
Most dam water goes to agriculture. Most agriculture uses overhead watering systems which, especially in hot climates, loses most of the spray to evaporation. It’s an expensive way to make clouds and a lousy way to grow wheat or maize.
Cities simply waste water. Even minimal water education backed by tough anti-waste laws would reduce urban industrial and home-use consumption by half. The battle cry shouldn’t be more power but better power conservation.
There can be only one conclusion: to halt dam construction and to blow useless and dangerous dams. A good practice run in what has been termed ‘dam decommissioning’ could be the Gariep Dam – formerly known as the Hendrik Verwoerd Dam – or the spooky Vanderkloof Dam lower down the Orange (it’s an unmanned machine).
Photo: Gariep Dam (Wikimedia commons)
There are a number of ways you could do it. First you draw down the water as far as possible, then you begin lowering the wall with pneumatic hammers and explosives. Finally, when the danger of water surge is sufficiently reduced, you dynamite the sucker.
If downstream users are the sort who bitch about muck in their water – and they’re bound to – you have to divert the flow, build coffer dams and blast sections of the wall inside them. The big expense, especially of it’s a mega hydro-dam with a 180-metre wall, is carting away all the rubble.
According to Bob Daphne of Wreckers Demolition, the cost will run to millions. But it could be done. “Just show me the wall,” he said.
Then again, a large amount of dynamite in the right place on some dark night could be spectacular. So if you’re not doing anything next weekend... DM
Photo: Katse Dam (Wikimedia commons)