Flow of many great rivers declining dramatically, according to new analysis

The flow of water in the world’s largest rivers has declined over the past half-century, with significant changes found in about a third of the big rivers.

A tow boat moves up the Mississippi River at the Port of New Orleans. The flow of water in the world’s largest rivers has declined over the past half-century

WASHINGTON — The flow of water in the world’s largest rivers has declined over the past half-century, with significant changes found in about a third of the big rivers.

An analysis of 925 major rivers from 1948 to 2004 showed an overall decline in total discharge.

The reduction in inflow to the Pacific Ocean alone was about equal to shutting off the Mississippi River, according to the new study appearing in the May 15 edition of the American Meteorological Society’s Journal of Climate.

The only area showing a significant increase in flow was the Arctic, where warming conditions are increasing the snow and ice melt, said researchers led by Aiguo Dai of the National Center for Atmospheric Research in Boulder, Colo.

“Freshwater resources will likely decline in the coming decades over many densely populated areas at mid- to low latitudes, largely due to climate changes, Dai said.

“Rapid disappearing mountain glaciers in the Tibetan plateau and other places will make matters worse.”

Added co-author Kevin Trenberth, “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.”

While Dai cited climate change as a major factor in the changes, the paper noted that other factors are also involved, including dams and the diversion of water for agriculture and industry.

Nonetheless, he said, “long-term changes in streamflow should be a major concern under global warming.”

Indeed, the researchers wrote that “for many of the world’s large rivers the effects of human activities on yearly streamflow are likely small compared with that of climate variations during 1948-2004.”

“This is an important paper with new findings that are relevant to the health of river ecosystems and the people who live near or rely upon rivers to meet water needs,” said Margaret Palmer, director of the Chesapeake Biological Laboratory of the University of Maryland Center for Environmental Science.

“What is important from this study is these authors show that these decreases are due to a changing climate, not human activities like extractions or dam building, yet these changes will have impacts on humans and ecosystems because many of these regions have large populations and drought-stressed ecosystems,” said Palmer, who was not part of the research team.

Among the rivers showing declines in flow, several serve large populations. These include the Yellow River in northern China, the Ganges in India, the Niger in West Africa and the Colorado in the southwestern United States.

On the other hand, areas with rising streamflow near the Arctic Ocean tend to have small populations.

There was considerable year-to-year variation in the flow of many rivers, but the overall trend over the period showed annual freshwater discharge into the Pacific Ocean fell by about six per cent, or 526 cubic km of water. That’s close to the 552-cubic km average annual flow of the Mississippi, the researchers reported.

The annual flow into the Indian Ocean dropped by about three per cent, or 140 cubic km.

In contrast, annual river discharge into the Arctic Ocean rose about 10 per cent, or 460 cubic km.

There was little change in inflow to the Atlantic Ocean, where increases in the Mississippi and Parana rivers were balanced out by decreases in the Amazon River.

A cubic km is a cube one km on each side. A km is about six-tenths of a mile.

Just Posted

Tory MPs gather in Red Deer to hear from voters

Eight MPs from across the province got input on a wide range of topics

Red Deer food bank to re-evaluate to stay up to date on new Canadian food guide

The Red Deer Food Bank Society, which feeds thousands of families every… Continue reading

Young Blackfalds mother copes with double tragedies with community support

Three fundraisers are being held to help Alana Newbold and her children

Red Deer careful about overuse of road salt

Focus on anti-icing to reduce salt use

Carjacking victim would stop to help again

Springbrook woman has some sympathy for carjacker

2-for-1: Total lunar eclipse comes with supermoon bonus

On Sunday night, the moon, Earth and sun lined up to create the eclipse, which was visible throughout North and South America

Liberals have options to help more millennials buy homes, experts say

OTTAWA — The federal Liberals have several options as they look for… Continue reading

Parks Canada puts brakes on Icefields Parkway bike trail in Alberta

Parks Canada says it won’t go ahead with a plan to build… Continue reading

Sylvan Lake resident to receive kidney from younger sister

Sylvan Lake resident Lexie Libby had been losing hope of ever finding… Continue reading

Closing arguments at trial of accused in slaying of Calgary Stampeders player

CALGARY — Final arguments are to be heard today at the trial… Continue reading

Edmonton Oilers fire general manager Peter Chiarelli: reports

EDMONTON — Peter Chiarelli has been fired as general manager of the… Continue reading

Canadian Milos Raonic has Australian Open run end in quarterfinals

MELBOURNE, Australia — Canadian Milos Raonic is done at the Australian Open… Continue reading

$20K pay gap between women, men in Canadian tech jobs

The report defines tech workers as people either producing or making extensive use of technology, regardless of industry

Two Quebec short-film directors mark first Oscar nominations together

TORONTO — Two Quebec filmmakers celebrated in solidarity on Tuesday after learning… Continue reading

Most Read