2005 – The Environmental Sustainability of Large Dams Compare with Other Sources of Water Supply

Robert Humphries, Caroline Minton, Andrew Baker and Mark Leathersich

There is a constant stream of criticism levelled at the perceived or actual adverse environmental
effects of large dams. These criticisms include prevention of fish migration, thermal and chemical and biological disturbance of downstream riverine habitats, silt trapping and drowning of terrestrial
habitats by flooding behind the dam wall. The beneficial effects of dams are rarely discussed, but
include aquatic habitat creation, catchment protection, flood mitigation, carbon sequestration and
protection of endangered species, amongst others.

Critics of large dams rarely present an analysis of the environmental costs and benefits of other water supply options, which include abstraction of shallow or deep groundwater, desalination of seawater, and reclamation of human or other wastewater.

In this paper we compare the environmental costs and benefits of water supply from large dams with
the common alternative options, and assess the relative sustainability of them all.