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Singley, Joel G ¹ ; Wlostowski, Adam N ² ; Bergstrom, Anna J ³ ; Sokol, Erick R ⁴ ; Torrens, Christa L ⁵ ; Jaros, Chris ⁶ ; Wilson, Colleen E ⁷ ; Gooseff, Michael N ⁸

¹ Environmental Studies Program, University of babyÖ±²¥app Boulder
² Department of Civil, Environmental, and Architectural Engineering, University of babyÖ±²¥app Boulder
³ Department of Geological Sciences, University of babyÖ±²¥app Boulder
⁴ Institute of Arctic and Alpine Research, University of babyÖ±²¥app Boulder
⁵ Environmental Studies Program, University of babyÖ±²¥app Boulder
⁶ Institute of Arctic and Alpine Research, University of babyÖ±²¥app Boulder
⁷ Department of Civil, Environmental, and Architectural Engineering, University of babyÖ±²¥app Boulder
⁸ Department of Civil, Environmental, and Architectural Engineering, University of babyÖ±²¥app Boulder

The analysis of concentration-discharge (C-Q) relationships has often been used in an inverse modeling framework to quantify source water contributions and biogeochemical processes occurring within catchments, especially during discrete hydrological events. Yet, the interpretation of C-Q hysteresis is often confounded by catchment complexity, such as a large number of source waters and non-stationarity in their hydrochemical composition. Attempts to overcome these challenges often necessitate ignoring or lumping together potentially important runoff pathways and geochemical sources/sinks. This is especially true of the hyporheic zone because it acts as an integrator of multiple sources and typically lacks a unique hydrochemical signature. Furthermore, these complexities often limit efforts to identify catchment processes responsible for the transience of C-Q hysteresis between discrete hydrological events. To address these challenges, we leverage the hydrologic simplicity and long-term, high frequency Q and electrical conductivity (EC) data from streams in the McMurdo Dry Valleys, Antarctica. In this two end-member system, EC can serve as a proxy for the concentration of solutes derived from the hyporheic zone and reveal the legacy of mixing processes occurring along the stream. We utilize a novel approach to decompose loops into sub-hysteretic EC-Q dynamics in order to identify individual mechanisms governing hysteretic patterns and transience across a wide range of timescales. From this analysis, we find that hydrologic and hydraulic processes govern EC response to diel and seasonal Q variability resulting in discrete hysteretic behavior. We also observe that variable hyporheic turnover rates govern EC-Q patterns at daily, annual, and interannual timescales and contribute differently to transient hysteresis in short and long streams. The framework we utilize to analyze sub-hysteretic dynamics may be applied more broadly to constrain the processes controlling C-Q transience and aid advancements in understanding the evolution of catchment processes and structure over time.