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Steps dominate gas evasion from a mountain headwater stream
Gianluca Botter1, Anna Carozzani2, Paolo Peruzzo2
1Department of Civil, Environmental and Architectural Engineering, University of Padua, via Marzolo 9, 35131, Padua (PD), Italy. gianluca.botter@dicea.unipd.it.
Nature Communications
|December 17, 2022
Summary
River steps significantly impact gas evasion, especially at high and low flows. These findings suggest current models may underestimate global river gas fluxes, highlighting the importance of small-scale river morphology.
Area of Science:
- Geomorphology
- Environmental Science
- Biogeochemistry
Background:
- Steps are key geomorphic features in high-energy rivers, influencing gas processing and exchange.
- Understanding how small-scale features affect large-scale gas evasion remains a challenge.
Purpose of the Study:
- To assess the contribution of localized steps to gas evasion in river networks.
- To integrate theoretical and experimental methods for evaluating gas fluxes.
Main Methods:
- Applied a framework combining theoretical and experimental approaches.
- Measured carbon dioxide concentrations across steps and a step-free segment in a 1km mountain reach in Italy.
- Evaluated gas evasion under varying hydrologic conditions.
Main Results:
- Localized steps were found to drive reach-scale gas outgassing.
- This effect was particularly pronounced during both high and low discharge events.
- Steps represent critical, yet overlooked, components in gas flux scaling laws.
Conclusions:
- River steps are crucial for accurate assessment of gas evasion.
- Existing scaling laws for gas fluxes may need revision to include step morphology.
- Global estimates of riverine gas evasion may require substantial upward adjustment.
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