Carbon dioxide emissions from rivers, lakes, and reservoirs are mainly driven by organic matter breakdown. When CO2 levels in water exceed those in the air, CO2 is released, but questions linger about how much is produced and its sources. Researchers’ new approach helps bridge this knowledge gap by offering detailed estimates.
Matthew Winnick, assistant professor of Earth, Geographic, and Climate Sciences at UMass Amherst, highlights the importance of this data: “Understanding CO2 production is essential for predicting responses to climate change.” He notes that higher temperatures could accelerate natural carbon processes, potentially intensifying climate impacts.
Traditional estimates averaged CO2 levels over large regions, overlooking variations between waterways. "A turbulent stream releases CO2 more rapidly,” Winnick explains, while headwater streams have distinct dynamics due to groundwater influx. The new method calculates emissions by simulating carbon movement in individual stream sections for more accurate results.
Winnick’s team, including co-lead author and graduate student Brian Saccardi, partnered with Colin Gleason and Craig Brinkerhoff to apply their model across 22 million U.S. stream reaches. This model estimated emissions at 120 million metric tons of carbon—25% lower than prior models. “Mountain regions play a significant role in national CO2 emissions, shifting the overall carbon budget,” Winnick says.
These findings could inform carbon sequestration projects introducing calcium carbonate minerals to stabilize CO2 in rivers. Winnick emphasizes that scientists need a precise understanding of CO2 distribution in waterways to gauge these projects' effectiveness.
Debates continue whether CO2 in rivers originates from groundwater or near-stream sediments. Winnick’s research points to the stream corridor as the primary source, but further studies are needed to confirm this and refine models for predicting emissions under climate change.
This study, funded by the U.S. National Science Foundation, could serve as a blueprint for future research on carbon cycling in North America and beyond aquatic systems.
