Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Umeå researchers have mapped the dams of the world


More than half of the world’s large rivers are fragmented and regulated by dams. The largest and the most biologically and geographically diverse rivers are all affected. This is shown by a global study that is published in this week’s issue of the journal Science.

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.

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.

The study shows that flow in 172 of the 292 largest rivers is regulated by dams. This number would be larger if irrigation were included. There are dams in the world’s 21 largest rivers and in the eight rivers that are biologically and geographically most diverse. The rivers in temperate forests and savannahs belong to the highest impact class, whereas many rivers in the tundra and in northern coniferous forests still remain free-flowing.

– 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.

Today, there are more than 45 000 dams over 15 meters high and that together can store more than 6500 km3 of water. This equals 15 percent of the annual freshwater runoff in the world. Over 300 dams are considered giants, over 150 meters high or storing more than 25 km3 of water. The recently built Three Gorges dam on the Yangtze River in China is the largest – 181 meters high and with a storage capacity of over 39 km3.

The study’s results will affect the assessment of how future climate changes and the constantly increasing use of water will impact the rivers’ ecosystems in different parts of the world.

The name of the article is Fragmentation and Flow Regulation of the World’s Large River Systems and is published in Science on April 15, 2005.

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.

Karin Wikman | alfa
Further information:

More articles from Ecology, The Environment and Conservation:

nachricht Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide

nachricht Malaysia's unique freshwater mussels in danger
27.09.2016 | The University of Nottingham Malaysia Campus

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>