Rivers, Streams Release Far More Carbon Dioxide Than Do Lakes: Study
December 10, 2013

Rivers, Streams Release Far More Carbon Dioxide Than Do Lakes: Study

April Flowers for redOrbit.com - Your Universe Online

Contrary to common belief, rivers and streams release carbon dioxide (CO2) into the atmosphere at a rate five times greater than the world's lakes and reservoirs combined. The findings of this international study, which included the University of Waterloo, have been published in the journal Nature.

"Identifying the sources and amounts of carbon dioxide released from continental water sources has been a gap in understanding the carbon cycle. Our findings show just how much carbon dioxide inland waters release and identified that rivers and streams are the main source not lakes and reservoirs, as previously thought,” said Professor Hans Dürr, research professor from the Faculty of Science at Waterloo.

The team, which included scientists from Belgium, Canada, Finland, France, Germany and the US, discovered that the rate at which lakes and reservoirs release CO2 -- known as the evasion rate -- was lower than previously estimated. Rivers and streams were three times greater, with smaller, faster moving streams being even higher. The team found that the global CO2 evasion rate from rivers and streams was 1.8 billion tons of carbon per year. In comparison, lakes and reservoirs have an evasion rate of 0.32 billion tons.

Professor Dürr, a member of the Ecohydrology Research Group and Water Institute at Waterloo, used a modeling tool he developed called Coastal Segmentation and related Catchments, or COSCAT, which was critical to putting the data into the global context.

"This study is an example of how new knowledge can be gained by bringing together different tools, techniques and ideas from hundreds of scientists to tackle a global issue," said Professor Dürr. "More integrated, international collaborations like this are needed."

COSCAT is a global database of water bodies, or catchments, that connect to oceans. This connection between land and ocean is important for the movement of nutrients, greenhouse gases and metals in water systems.

The findings will provide new insights into how rivers and streams affect the global carbon cycle. They will also emphasize the need for additional research to determine the carbon dioxide evasion rate for inland waters in the northern hemisphere.

More accurate estimates of CO2 emissions are crucial because climate models project higher temperature increases than the global average in latitudes higher than 60 degrees north. Many of the tools, however, are derived from satellite products that do not yet exist for these latitudes.