Dam Census Shows Rivers Up A Creek Without A Paddle

Humans have drastically changed many rivers by impoundments and diversions to meet the needs of water, energy and transportation. Such exploitation belongs among the most dramatic, deliberate impacts that humans have had on the natural environment. Many of the ecological effects of dams are relatively well known. Despite this fact, there has so far not been any overview of how this impact is distributed globally.

The Umeå based research group now presents an overview of how the world’s large rivers are regulated and fragmented by dams. The researchers examined the world’s rivers with a mean annual flow of at least 350 m3/s (e.g., larger than the Torne River in northern Sweden). The only regions for which accurate data have not been available are Indonesia and a small part of Malaysia.

– When comparing continents, Europe has the highest proportion of strongly impacted rivers whereas Australia, including New Zealand and Papua New Guinea, has the largest proportion of free-flowing rivers. Overall, the degree of impact relates to population density and economic development. The few river systems that buck this trend are in places such as northern Canada, where dams were built in sparsely populated areas for the export of electricity and/or water, says Christer Nilsson.

The research project has amongst others been funded by WWF Sweden, United Nations Educational, Scientific and Cultural Organization (UNESCO)/World Water Assessment Programme, United Nations Environment Programme (UNEP) and World Resources Institute. Christer Nilsson was last autumn funded by the Swedish Research Council to continue his study. His research group will now investigate how the dams have affected the vulnerability of freshwater fish.

Behind the study are Christer Nilsson, Cathy Reidy and Mats Dynesius at Umeå University and Carmen Revenga at The Nature Conservancy in the U.S.

From a SRC press release.