Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Water Levels Dropping in Some Major Rivers as Global Climate Changes

Rivers in some of the world's most populous regions are losing water, according to a new comprehensive study of global stream flow.

The study, led by scientists at the National Center for Atmospheric Research (NCAR), suggests that in many cases the reduced flows are associated with climate change. The process could potentially threaten future supplies of food and water.

The results will be published May 15 in the American Meteorological Society's Journal of Climate. The research was supported by the National Science Foundation, NCAR's sponsor.

The scientists, who examined stream flow from 1948 to 2004, found significant changes in about one-third of the world's largest rivers. Of those, rivers with decreased flow outnumbered those with increased flow by a ratio of about 2.5 to 1.

Several of the rivers channeling less water serve large populations, including the Yellow River in northern China, the Ganges in India, the Niger in West Africa, and the Colorado in the southwestern United States. In contrast, the scientists reported greater stream flow over sparsely populated areas near the Arctic Ocean, where snow and ice are rapidly melting.

"Reduced runoff is increasing the pressure on freshwater resources in much of the world, especially with more demand for water as population increases," says NCAR scientist Aiguo Dai, the lead author. "Freshwater being a vital resource, the downward trends are a great concern."

Many factors can affect river discharge, including dams and the diversion of water for agriculture and industry. The researchers found, however, that the reduced flows in many cases appear to be related to global climate change, which is altering precipitation patterns and increasing the rate of evaporation. The results are consistent with previous research by Dai and others showing widespread drying and increased drought over many land areas.

The study raises wider ecological and climate concerns. Discharge from the world's great rivers results in deposits of dissolved nutrients and minerals into the oceans. The freshwater flow also affects global ocean circulation patterns, which are driven by changes in salinity and temperature and which play a vital role in regulating the world's climate. Although the recent changes in the freshwater discharge are relatively small and may only have impacts around major river mouths, Dai said the freshwater balance in the global oceans needs to be monitored for any long-term changes.

Conflicting studies

Scientists have been uncertain about the impacts of global warming on the world's major rivers. Studies with computer models show that many of the rivers outside the Arctic could lose water because of decreased precipitation in the mid- and lower latitudes and an increase in evaporation caused by higher temperatures. Earlier, less comprehensive analyses of major rivers had indicated, however, that global stream flow was increasing.

Dai and his co-authors analyzed the flows of 925 of the planet's largest rivers, combining actual measurements with computer-based stream flow models to fill in data gaps. The rivers in the study drain water from every major landmass except Antarctica and Greenland and account for 73 percent of the world's total stream flow.

Overall, the study found that, from 1948 to 2004, annual freshwater discharge into the Pacific Ocean fell by about 6 percent, or 526 cubic kilometers--approximately the same volume of water that flows out of the Mississippi River each year. The annual flow into the Indian Ocean dropped by about 3 percent, or 140 cubic kilometers. In contrast, annual river discharge into the Arctic Ocean rose about 10 percent, or 460 cubic kilometers.

In the United States, the Columbia River's flow declined by about 14 percent during the 1948-2004 study period, largely because of reduced precipitation and higher water usage in the West. The Mississippi River, however, has increased by 22 percent over the same period because of greater precipitation across the Midwest since 1948.

The impacts of melting

Some rivers, such as the Brahmaputra in South Asia and the Yangtze in China, have shown stable or increasing flows. But they could lose volume in future decades with the gradual disappearance of the Himalayan glaciers feeding them, the authors warned.

"As climate change inevitably continues in coming decades, we are likely to see greater impacts on many rivers and water resources that society has come to rely on," says NCAR scientist Kevin Trenberth, a co-author of the study.

David Hosansky | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

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 >>>