Advocates of small hydro present it as a relatively low-impact source of energy, with scope for global expansion. As rocketing energy prices and fears of blackouts, along with climate change, accelerate the quest to find alternatives to coal, gas and oil, the idea of a robust, renewable local energy source may sound very appealing. But critics argue that the ecological cost of small plants may be higher than previously thought – and needs to be carefully balanced against their benefits.

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