Oral Presentations and Performances: Session I
Project Type
Presentation
Project Funding and Affiliations
Geosciences
Faculty Mentor’s Full Name
Payton Gardner
Faculty Mentor’s Department
Geosciences
Abstract / Artist's Statement
Gas exchange velocity (K) was measured on the Upper Clark Fork River (UCFR) across three seasonal flow regimes to constrain estimates of K used in a dissolved radon groundwater flux model. Dissolved oxygen sensors were deployed at two stations 75 km apart during June (peak runoff), July (irrigation-induced low flow), and October (natural baseflow) for periods of 3-10 days. Gas exchange velocity normalized to a Schmidt number of 600 (K600) was calculated using a two-station Bayesian model, a one-station Bayesian model, nighttime regressions of dissolved O2 and O2 saturation deficit, and energy dissipation scaling relationships. Bayesian models failed to produce physically meaningful parameter estimates due to parameter equifinality between K600 and ecosystem respiration. Nighttime regressions yielded an average K600 of 10.1 ± 5.0 m d-1 during peak flow, 9.5 ± 1.1 m d-1 during irrigation induced low flow, and 8.7 ± 0.7 m d-1 during natural baseflow with differences of up to 5.5 m d-1 between the upper and lower stations. Nighttime regression k600 values fell within the expected range based on established energy dissipation scaling relationships, and significant differences between upstream and downstream stations indicate that gas exchange varies spatially across the 75 km reach. These findings provide seasonal k600 constraints for radon-based groundwater flux modeling on the Upper Clark Fork River and demonstrate that a single reach-averaged value would inadequately represent the spatial variability in gas exchange across this system.
Category
Physical Sciences
Gas Exchange Velocity Variation on the Upper Clark Fork River
UC 327
Gas exchange velocity (K) was measured on the Upper Clark Fork River (UCFR) across three seasonal flow regimes to constrain estimates of K used in a dissolved radon groundwater flux model. Dissolved oxygen sensors were deployed at two stations 75 km apart during June (peak runoff), July (irrigation-induced low flow), and October (natural baseflow) for periods of 3-10 days. Gas exchange velocity normalized to a Schmidt number of 600 (K600) was calculated using a two-station Bayesian model, a one-station Bayesian model, nighttime regressions of dissolved O2 and O2 saturation deficit, and energy dissipation scaling relationships. Bayesian models failed to produce physically meaningful parameter estimates due to parameter equifinality between K600 and ecosystem respiration. Nighttime regressions yielded an average K600 of 10.1 ± 5.0 m d-1 during peak flow, 9.5 ± 1.1 m d-1 during irrigation induced low flow, and 8.7 ± 0.7 m d-1 during natural baseflow with differences of up to 5.5 m d-1 between the upper and lower stations. Nighttime regression k600 values fell within the expected range based on established energy dissipation scaling relationships, and significant differences between upstream and downstream stations indicate that gas exchange varies spatially across the 75 km reach. These findings provide seasonal k600 constraints for radon-based groundwater flux modeling on the Upper Clark Fork River and demonstrate that a single reach-averaged value would inadequately represent the spatial variability in gas exchange across this system.