Moving Bedforms Control CO₂ Production and Distribution in Sandy River Sediments

Abstract

Freshwater systems play an important role in the global carbon (C) cycle (Battin et al., 2009). The C originating from terrestrial sources is stored in aquatic sediments, exported to the ocean, or evaded to the atmosphere in the form of CO 2 (Cole et al., 2007;Raymond et al., 2013;Regnier et al., 2013). Most research on CO 2 evasion from rivers considers the river system as a "black box" where origins of CO 2 are often poorly constrained or neglected (

The Fragility of Bedform‐Induced Hyporheic Zones: Exploring Impacts of Dynamic Groundwater Table Fluctuations

“…The fragility of bedform‐induced advective pumping emphasizes the importance and need for more research attention and considerations of other types of hyporheic exchanges, that is, near‐bed turbulence and turnover (Grant et al., 2018; Nagaoka & Ohgaki, 1990; Roche et al., 2018; Schulz et al., 2023). Although these two types of hyporheic exchange may also potentially be affected by large gradients between surface water and groundwater hydraulic heads, there is still a lack of evidence to quantify how fragile these processes would be.…”

“…The main mechanisms driving bedform‐induced hyporheic exchange include (a) spatial variation in near‐bed pressure head (bedform‐induced advective pumping), (b) near‐bed turbulence, and (c) bedload transport (turnover) (Boano et al., 2014; Buffington & Tonina, 2009; Tonina & Buffington, 2009). Even though these processes co‐occur, and their relative importance depends on channel hydraulic conditions, streambed properties, and regional groundwater flow (hereafter understood as the boundary fluxes contributed by the overall groundwater fluxes from the lower streambed), bedform‐induced advective pumping has received significantly more attention (Boano et al., 2014; Grant et al., 2018; Schulz et al., 2023; Wu et al., 2020) and is at the core of most upscaling frameworks for hyporheic exchange (e.g., Azizian et al., 2015, 2017; Elliott & Brooks, 1997; Gomez‐Velez & Harvey, 2014a; Herzog et al., 2019; Marzadri et al., 2011, 2014; Perez et al., 2021; Stonedahl et al., 2010, 2012, 2013; Wörman et al., 2006, 2007). This emphasis can be partially explained by its intuitive conceptualization.…”