Stream Corridor Hydrologic Controls on Carbon Dioxide Fluxes

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Rivers and streams are increasingly recognized as important sources of greenhouse gases such as carbon dioxide (CO2) to the atmosphere; however, the full magnitude of emissions and the processes that control them remain highly uncertain. This project will combine innovative field characterizations of stream hydrology and carbon processing with advanced computer models to improve our ability to predict and scale stream CO2 fluxes. Results of this research will advance our understanding of an important component of the global carbon cycle and the ability to monitor changes into the future, and generated computer models will be made publicly available. This research will also comprise the training of a PhD student and undergraduate researcher, and it will serve as the focus of a 1-day educational module for a diverse group of high school students through the Rocky Mountain Biological Laboratory’s summer Field Biology course.The primary objective of this project is to develop quantitative models of stream corridor hydrologic processes, their controls on watershed-level stream CO2 fluxes, and their spatial and temporal modes of variability. Through intensive field monitoring of the upper East River watershed in the Colorado Rocky Mountains, the project will address a number of research goals: (1) Provide direct observations of groundwater inputs to streams using high resolution temperature mapping and geochemical characterization to understand their contributions to CO2 fluxes and role in driving spatiotemporal variability through connectivity and flowpath variations; (2) Disentangle in-stream CO2 production between water-column and hyporheic zone sources and characterize the dominant processes that control CO2 exchange with the hyporheic zone through a series of reach-scale monitoring efforts and tracer release experiments; (3) Incorporate process-based representations of groundwater inputs and stream corridor production, along with transport and turbulent gas exchange, into reach- and watershed-scale stream network models of CO2 to improve predictions and monitoring of stream concentrations and fluxes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.