Temporal Variations in Dissolved Oxygen Concentrations Observed in a Shallow Floodplain Aquifer: Fid-Bau Portal

Temporal Variations in Dissolved Oxygen Concentrations Observed in a Shallow Floodplain Aquifer

Schilling, K. E. / Jacobson, P. J.

Dissolved oxygen (DO) concentrations play an important role in many groundwater biogeochemial processes, yet assessments of temporal variations are lacking. In this study, we examined daily DO concentrations using a continuously‐reading optical DO probe in a shallow floodplain setting in Iowa to (i) quantify fluctuations across two growing seasons; (ii) examine hydrologic controls on DO values; and (iii) model daily DO concentrations using easily measured variables. DO concentrations exhibited both rapid and long‐term changes in concentrations over time, rapidly increasing and decreasing more than 1 mg/l in response to precipitation recharge and stream stage increase over the span of several hours and days. On 40% of the monitoring days in this study, DO concentrations increased, on average, 0.2–0.4 mg/l from one day to the next. DO concentrations decreased approximately 5–6 mg/l from spring through late summer and fall, likely owing to microbial and root respiration. Daily DO concentrations were successfully modelled using a combination of hydrologic (groundwater level and river stage) and temperature variables (r² > 0.7). Improved understanding of temporal controls on groundwater DO patterns is needed to help clarify the dynamics of many biogeochemical processes. Copyright © 2014 John Wiley & Sons, Ltd.