It is clear that the facts given in this passage about dams ----.

The report, Dams and Development, which has been
recently published, provides stark evidence that the
world's 45,000 large dams which block over half of
the world's rivers, have been failed experiments.
They have failed to produce as much electricity and
water, or control as much flood damage, as their
backers claim. They regularly suffer huge costoverruns
and time delays. They have made up to 80
million people homeless, and their benefits have
largely gone to the urban well-off not the rural poor
they displace. Moreover, their effects on ecosystems
have been disastrous.