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Grad student talk - Sub-hysteretic analysis: Transient EC-Q relationships and hyporheic exchange

Thursday, March 23, 2017, 12:30PM - 1:30PM


Joel Singley



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. 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. We use a novel approach to decompose hysteretic 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 use 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.