Prediction of Hypoxia in Eutrophic Polymictic Lakes. Issue 6 (4th June 2021)

• Record Type: Journal Article
• Authors: Cortés, A.; Forrest, A. L.; Sadro, S.; Stang, A. J.; Swann, M.; Framsted, N. T.; Thirkill, R.; Sharp, S. L.; Schladow, S. G.
• Is Part Of: Water resources research. Volume 57:Issue 6(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-06-04
• Subjects: hypoxia -- polymictic lake -- eutrophic lake -- surface heat fluxes -- lake number -- 1‐D methods; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2020WR028693
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Quantifying and predicting the drawdown of dissolved oxygen (DO) in lakes is important to ensuring healthy ecosystems and safe water sources. The characterization of DO depletion using available definitions and models requires extensive monitoring to obtain reliable results. These approaches have been mostly developed for seasonally stratified monomictic and dimictic lakes, limiting their applicability for polymictic systems which stratify and mix repeatedly. We compared the predicted duration of hypoxic events in the three basins of a large eutrophic polymictic lake (Clear Lake, CA, USA) by using three different one‐dimensional (1‐D) analytical approaches; two being original and requiring minimal input variables. Data on meteorology, lake temperature, and DO were all measured at multiple locations for one year and used to develop a novel method, named the Birge‐Winkler method. The daily net surface heat fluxes provided an energy term from which estimates of the onset and length of hypoxic periods could be made with minimal calibration. We used the Lake Number method to evaluate the level of accuracy of the Birge‐Winkler method. Finally, we estimated DO values next to the sediments using a Buoyancy Frequency method. Our results from the two original methods provided simple and effective tools for early warning of onset and duration of hypoxia, with a maximum of ±3–5 days uncertainty in the predictions. These indices can become powerful decision support tools for addressing aquatic ecological challenges triggered by hypoxia, including fish kills, internal nutrient loading, heavy metals release, and harmful algal blooms. Key Points: We present a new one‐dimensional method to estimate onset and duration of hypoxic events in eutrophic polymictic lakes The model only requires basic meteorological variables, lake surface temperatures, and dissolved oxygen at the lake bottom for calibration The method can be a cost‐effective decision‐making tool for management actions affecting ecosystem health and water quality