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SFS Annual Meeting

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MOVING FROM CONCENTRATION-DISCHARGE CURVES TO PROCESS-DISCHARGE RELATIONSHIPS

Concentration-discharge (CQ) analyses have traditionally been used to explain solute fluxes driven by catchment connectivity; yet the prevalence of nonlinear CQ relationships can inform the complex dynamics of stream processes across variable flows. Using two years of high-frequency data from three stream reaches with varying land use and riparian connectivity (urban drainage, urban-agricultural, and agricultural with restored floodplain connections), we examined the influence of lateral connectivity and catchment morphology on physicochemical-discharge breakpoints in segmented regressions. Statistically-derived changes in slope were significant (p < 0.05) across all parameters (dissolved oxygen, temperature, pH, turbidity, conductivity), and CQ slopes displayed chemodynamic and chemostatic trends, exhibiting four of the possible CQ modalities. Slope breakpoints relative to median flow were used as indicators of catchment connectivity. In the urban reach CQ slopes were segmented after median flow, while slope breakpoints within the restored agricultural reach occurred before median flow and signified enhanced connectivity with riparian floodplains. The change of slopes at the urban-agricultural intermediary site varied relative to median flow. Ongoing research compares nonlinear CQ relationships of bioreactive parameters (e.g., dissolved oxygen) to ecosystem metabolism to elucidate the relationship between CQ curves and process-discharge responses.

Erin Hotchkiss (Co-Presenter/Co-Author), Virginia Tech, ehotchkiss@vt.edu;


Brynn ODonnell (Primary Presenter/Author), Virginia Tech, brynno@vt.edu;