Even the worst hydroelectric dam is cleaner than the best hydrocarbon burner, and renewable to boot.

There has been a lot of controversy about China's hydroelectric projects, particularly the Three Gorges Dam, with people losing homes, historical sites being lost, and other issues.

However, when completed, this dam will throw off 18,200 MW, about a tenth of China's current requirements. That's one HELL of a lot of non-renewable coal not being mined and burned into particulates and CO2.

The problem some environmentalists have been having with hydroelectrics is a relatively recent phenomenon in environmentalism, where it isn't enough to not poison an environment, you can't even change it.

If humans do it, it's bad, even if the altered environment is benign, and just fine with the rest of the ecosystem (dams with fish ladders, etc). Most recent example of this is out here in California, where environmentalists are trying to get the Hetch Hetchy reservoir, where the water from MY faucet comes from, torn down.

Why? Because it's filling a scenic canyon that used to be there. Is the lake scenic? Sure, but it's not NATURAL scenic, see?. If an avalanche had closed the river opening a thousand years ago, and created the same lake, it would be no doubt be accepted by the same environmentalists who would then be aghast if someone wanted to drain it to see what the canyon looked like.

Interestingly, Yosemite Valley, similar to the Hetch Hetchy location, apparently had once been closed off by such a natural barrier, and was mostly lake.