June 2011: The tiny eastern Himalayan state of Sikkim, known for
its stunning forest vistas and amazing biodiversity, is under
threat from the cumulative impacts of close to 30 large
hydroelectric projects. While several are already under
construction or completed, many more are at various stages of
clearance. Most of the so called ‘run-of-the-river’
hydroelectric projects being developed involve large dams which
divert the river waters through long tunnels, before the water
is dropped back into the river at a downstream location after
passing through a powerhouse. These projects are promoted as
being ‘environmentally benign’ as they involve smaller
submergences and lesser regulation of water as compared to
conventional storage dams. This perception conveniently ignores
the impact of several features intrinsic to this design. For
example, long stretches of the river will be bypassed between
the dam and powerhouse, with up to 85 – 90 per cent of the flow
in the winter (lean season) diverted through the tunnels