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Abstract Inland waters are an important component of the global carbon budget. However, our ability to predict carbon fluxes from stream systems remains uncertain, aspCO2varies within streams at scales of 1–100 m. This makes direct monitoring of large‐scale CO2fluxes impractical. We incorporate CO2input and output fluxes into a stream network advection‐reaction model, representing the first process‐based representation of stream CO2dynamics at watershed scales. This model includes groundwater (GW) CO2inputs, water column (WC), benthic hyporheic zone (BHZ) respiration, downstream advection, and atmospheric exchange. We evaluate this model against existing statistical methods including upscaling and multiple linear regressions through comparisons to high‐resolution streampCO2data collected across the East River Watershed in the Colorado Rocky Mountains (USA). The stream network model accurately captures GW, evasion, and respiration‐drivenpCO2variability and significantly outperforms multiple linear regressions for predictingpCO2. Further, the model provides estimates of CO2contributions from internal versus external sources suggesting that streams transition from GW‐ to BHZ‐dominated sources between 3rd and 4th Strahler orders, with GW, BHZ, and WC accounting for 49.3%, 50.6%, and 0.1% of CO2fluxes from the watershed, respectively. Lastly, stream network model atmospheric CO2fluxes are 4‐12x times smaller than upscaling technique predictions, largely due to relationships between streampCO2and gas exchange velocities. Taken together, this stream network model improves our ability to predict stream CO2dynamics and efflux. Furthermore, future applications to regional and global scales may result in a significant downward revision of global flux estimates.
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This content will become publicly available on December 1, 2025
Toward Modeling Continental‐Scale Inland Water Carbon Dioxide Emissions
Abstract Inland waters emit significant amounts of carbon dioxide (CO2) to the atmosphere; however, the global magnitude and source distribution of inland water CO2emissions remain uncertain. These fluxes have previously been “statistically upscaled” by independently estimating dissolved CO2concentrations and gas exchange velocities to calculate fluxes. This scaling, while robust and defensible, has known limitations in representing carbon source limitations and spatial variability. Here, we develop and calibrate a CO2transport model for the continental United States, simulating carbon transport and transformation in >22 million hydraulically connected rivers, lakes, and reservoirs. We estimate 25% lower CO2fluxes compared to upscaling estimates forced by the same observational calibration data. While precise CO2source distribution estimates are limited by the resolution of model parameterizations, our model suggests that stream corridor CO2production dominates over groundwater inputs at the continental scale. Our results further suggest that the lack of observational networks for groundwater CO2and scalable metabolic models of aquatic CO2production remain the most salient barriers to further coupling of our model with other Earth system components.
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- PAR ID:
- 10574837
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- AGU Advances
- Volume:
- 5
- Issue:
- 6
- ISSN:
- 2576-604X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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