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Abstract Downstream flow in rivers is repeatedly delayed by hydrologic exchange with offâchannel storage zones where biogeochemical processing occurs. We present a dimensionless metric that quantifies river connectivity as the balance between downstream flow and the exchange of water with the bed, banks, and floodplains. The degree of connectivity directly influences downstream water quality--too little connectivity limits the amount of river water exchanged and leads to biogeochemically inactive water storage, while too much connectivity limits the contact time with sediments for reactions to proceed. Using a metric of reaction significance based on river connectivity, we provide evidence that intermediate levels...
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Rivers are the veins of the landscape, providing environmental benefits that are disproportionately high relative to their aerial extent; shedding flood waters, hosting aquatic ecosystems, transporting solutes and energy-rich materials, and storing and transforming pollutants into less harmful forms. From uplands to the coasts, rivers facilitate key biogeochemical reactions that cumulatively influence water quality. Many of the reactions are optimized outside the main channel, in hyporheic zones, riparian zones, and floodplain areas, where riverine water is in close contact with geochemically and microbially-active sediments. However, little is known about the distribution, intermittency, and overall effectiveness...
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