The Effect of Non-Steady Overlying Water Velocity on Oxygen Consumption Under Losing and Gaining Flow Conditions

J. A. Galloway, L. Wu, J. Lewandowski, S. Arnon

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Wastewater treatment plants which discharge treated effluent into river systems can drastically alter downstream flow regime from steady flow velocities to water velocities which fluctuate on a diurnal cycle. The impacts of flow variations are expected to have complex and non-linear impacts on the temporal and spatial redox dynamics within the hyporheic zone. The objective of the current study was to qualitatively describe the effect of non-steady flow on oxygen consumption under losing and gaining conditions. A novel system which allowed for precise control and modulation of pore water velocities was deployed in a specially designed, 260 cm-long by 29 cm-wide flume. Experiments were carried out under various vertical fluxes. Oxygen dynamics were investigated by using planar optodes to measure oxygen concentrations in the hyporheic zone at a high temporal and spatial resolution. These empirical measurements were then used as inputs for a reactive transport model allowing for the calculation of oxygen consumption rates. A complex interplay between direction and magnitude of surface water velocity changes as well as antecedent flow conditions was discovered and quantitatively described. The development and calibration of the model allowed us to explore the relationships discovered in a variety of scenarios. Overall, unsteady flow conditions lead to up to a 2-fold increase in the delivery of dissolved oxygen to the hyporheic zone and lead to a higher rate of oxygen consumption than would have been predicted by a comparable steady surface flow. Vertical fluxes reduce the magnitude of the effect of surface water perturbations. The results of the current study provide an insight into how anthropogenic changes to discharge regimes in river systems can impact the biogeochemistry of the hyporheic zone.
Original languageEnglish GB
Title of host publicationAmerican Geophysical Union, Fall Meeting 2017
Volume23
StatePublished - 1 Dec 2017

Publication series

NameAmerican Geophysical Union, Fall Meeting 2017

Keywords

  • 0414 Biogeochemical cycles
  • processes
  • and modeling
  • BIOGEOSCIENCES
  • 0496 Water quality
  • 1830 Groundwater/surface water interaction
  • HYDROLOGY
  • 1839 Hydrologic scaling

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