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Most of the world's 45,000 large dams don't do their jobs properly. So concludes the first ever global audit of a technology that has cost $2 trillion over the past century...

Dams generate hydroelectricity, prevent floods, irrigate farms and supply water to cities. But they have also wrecked ecosystems and "led to the impoverishment of millions", who lost their land to reservoirs or saw dams destroy their fisheries.

The report calls for an end to dams that are imposed on communities without their agreement. But its most remarkable findings are on the widespread technical failures of dams.

Studies carried out by the commission found that:

• One in four dams irrigate "less than 35 per cent" of the land they were supposed to

• The cost over-runs of construction are 56 per cent on average

• Two-thirds of dams deliver less water to cities than promised. A quarter delivered less than half the promised water

• Over half of hydroelectric dams do not generate as much power as promised

• Some flood-control dams "have increased the vulnerability of river communities to floods"

One reason many dams have failed to deliver is that their reservoirs have clogged up with silt far faster than expected. Every year an extra one per cent of the world's reservoir capacity is taken up with silt. In the worst cases, reservoirs lost more than 80 per cent of their storage capacity to silt in less than 30 years.

Macsporan wrote:The State shall pay in the common interest, financed by heavy taxation on the wealthy.

Are these failings the fault of the dams, or perhaps the result of lack of follow-up investment?

Not really part of anything, but when they filled Williston Lake during the early '70's it screwed up the weather for years. I expect it permanently changed it, however I didn't have the experience of the weather beforehand to compare to. I do remember the "oldtimers" discussing it though. From my own memory I do remember the winter of 1971. Moose everywhere in the Omenica Valley, bellying through five or six feet of snow, starving. The lowland willow flats of the Peace river were the moose' winter forage, they came down from the higher valleys of the upper Peace river, Omenica, Osilika, Ingenika, and Prophet Rivers, as well as other smaller rivers, to winter. When the resevoir flooded they lost that habitat in a season. I would guess that tens of thousands died, I was informed by a ministry of the enviroment biologist a few years back, long after the fact, that it was "only a handful of animals". That defies the evidence of my own eyes. Green power at work. For every action, a reaction.

Macsporan wrote:Yes, nostalgia isn't what it used to be.

Do all lakes emit methene or is this curse restricted to dams?

Pardon my scepticism but I think that the greenhouse gas damage of dam, even given that its methane not CO2, is going to be trifling compared to a coal, gas or oil plant.

As for damage to the environment hydro and nuclear aren't even on the same planet.

Build more dams, I say.

Build more of them.

redfire wrote:With today's technology do you have to dam a river to produce hydro power? I remember seeing a show on how small veriable pitch turbine generators could be installed in a river and you could not tell they where there. What if 10,000 of these type of generators were linked together?
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Now I found out that, even though Europeans have only been in NZ since 1840 they still found time to build a village and then decide to drown it.

Some place in the South Island, it was on TV on a program showing how much rail had been ripped up in NZ, I didn't know we had much to start with.

redfire wrote:With today's technology do you have to dam a river to produce hydro power? I remember seeing a show on how small veriable pitch turbine generators could be installed in a river and you could not tell they where there.

Tanada wrote:In Alaska it would allow Anchorage to shut down their coal power plants and switch to renewable power.