MDEQ-AQD Air Toxics Rules Overview and Regulatory Reinvention
Neither Wolf nor Dog: P-Management in a Quasi-Polymictic Lake€¦ · Kieser & Associates and...
1
Neither Wolf nor Dog: P-Management in a Quasi-Polymictic Lake Introduction Drowned river mouth lakes are common along the western shore of Lake Michigan. Hydrodynamically linked to the larger system, these small lakes receive intrusions of colder, cleaner water that impact thermal stratification (e.g. vertical mixing) and biogeochemical (e.g. sediment phosphorus flux) processes. Mona Lake (MI) has historically received wastewater effluent leading to its present eutrophic state. Wastewater diversion, implemented in 1972, has failed to improve trophic state conditions and the lake continues to experience hypolimnetic anoxia, elevated phosphorus levels and cyanobacteria blooms, with 2018 peak microcystin concentrations nearing 400 ug/L (DEQ Monitoring). The work reported here tests the hypothesis that water quality conditions in Mona Lake are driven by internal phosphorus loading. The role of the system’s weakly stratifying nature and intrusions from Lake Michigan in mediating recovery are explored. Study Site Description Stratification P Transport Trophic State References • Length of 6.5 km, average width of 0.5 km • Mean and maximum depths of 4.5 and 11.0 m • Oriented east-west, aligned with strong prevailing westerly winds over Lake Michigan. • HRT: 105 to 160 days during low tributary flows, less than 35 days during high flows 3 • Tributaries: ~90 percent of the hydrologic and phosphorus load enters the lake at its east end 5 Mona Lake stratifies ephemerally, i.e. exhibits metastable polymixis, driven by strong winds traveling parallel to its major axis. The system alternates between a thermally stratified state with oxygen depletion and soluble reactive phosphorus accumulation in the hypolimnion and a completely mixed state where oxygen is re- introduced to bottom water and phosphorus is transported to surface waters. • Seiches and surges from Lake Michigan can change water chemistry, stratification. • Hypothesis: colder migrant water increases the resistance to mixing, strengthens hypolimnion. Intrusions Current Conclusions Modeling Both intrusions and mixing events can be observed in hypolimnetic temperature variances during the ice-free sampling season. While Mona Lake has spatial differences in stratification regimes, vertical profiles showed heterogeneity-at-depth between sites, and thus, a 1D mass-balance modeling platform (LAKE2K) 2 is to be used to simulate physical and biogeochemical processes as a means to: • Identify maximum achievable external load-based trophic state • Testing external load reduction strategies • Quantify diffusion-based P transport4 Upon completion of further model confirmation and calibration, hypothetical loading scenarios are intended to form the basis for remedial and management action plans. Field data and empirical models support the hypothesis that Mona Lake is capable of assimilating it’s current external load – but trophic state improvements will not be made manifest until internal loading is addressed. Based on 2017 and 2018 field data, approximately 30 percent of Mona Lake possess a depth capable of stratification strong enough to result in anoxia, found to be ~6m. Thus, application of engineering approach management solutions may need only be present in a small area of the lake bottom, making some often cost- prohibitive approaches feasible. Beyond the established deliverables of this research, it aims to serve in increasing the understanding of other shallow, dynamic systems and how best they are managed. Figure 1. Mona Lake Watershed Area (Annis Water Resources Institute) Figure 2. Bathymetry, with imposed basins based on relative mean depth bins. Figure 3. Continuous temperature monitoring at a single deep site. Figure 4. Intrusion detection through conductivity profiles at westernmost field sites. Figure 5. Hypolimnetic temperature variances between sampling dates (2018). [1] Carlson, R. (1977). A trophic state index for lakes. Limnology and Oceanography 22. [2] Chapra, S., and Martin, J. (2004). LAKE2K: A Modeling Framework for Simulating Lake Water Quality (Version 1.2): Documentation and Users Manual. Civil and Environmental Engineering Dept., Tufts University, Medford, MA. [3] Evans, E. (1992). Mona, White, and Muskegon Lakes in Muskegon County, Michigan: the 1950s to the 1980s. Michigan Department of Natural Resources, Lansing, MI. MI/DNR/SWQ-92/261. [4] Limno-Tech. (1982). The Effect of Wastewater Land Treatment on Eutrophication in Muskegon County Lakes. [5] Steinman, A., Rediske, R., Denning, R., Nemeth, L., Chu, X., Uzarski, D., Luttenton, M. (2006). An environmental assessment of an impacted, urbanized watershed: the Mona Lake Watershed, Michigan. Arch. Hydrobiol., 166. Major Turnover Minor Major Intrusion Intrusion Wastewater diversion reduced the external phosphorus loading to Mona Lake by 75-80 percent from 1972 to 1981 4 . Analysis of changes in external phosphorus loading according to the Vollenweider (1975) model predicts a transition in trophic state from eutrophic (pre-diversion) to near mesotrophy (post-diversion). Water Quality Internal Loading Field measurements made in this study provide clear evidence of sediment-P release to hypolimnetic waters (rates of 10-12 mgP m -2 d -1 ) for the 30 days of anoxia occurring irregularly over the summer season. Increases in phosphorus levels in the epilimnion, an important trigger for algal blooms, are likely ascribable to wind- driven mixing events as tributary discharges are modest (at best) during summer and diffusive vertical mass transport is not of a sufficient magnitude to account for the rate of increase observed. Figures 6 and 7. Vollenweider (1975) loading plot and Carlson (1977) TSI. Figures 8 and 9. 2017 TP concentrations at deep sites and whole lake. Application of a trophic state index (TSI) 1 based on field measurements of water column conditions suggest minimal improvement occurred in response to wastewater diversion. This forms the basis of our hypothesis that internal loads govern trophic state conditions in the post-diversion period. Upwellings of highly bioavailable phosphorus-rich water, driven by vertical mixing events, lead to discernible increases in surface water phosphorus. Chlorophyll and microcystin observations (MDEQ 2018) correlate well to the increase in phosphorus concentration. Figure 10. Observed TP concentrations , MDEQ chlorophyll and microcystin detection for 2018. Acknowledgements: George Cannon Scholarship, Mona Lake Watershed Council, Kieser & Associates and Michelle Storey (MDEQ) Hayden Henderson and Dr. Martin T. Auer Great Lakes Research Center at Michigan Technological University Presented at the 38th International Symposium of the North American Lake Management Society, Cincinnati, Ohio - October 30-2 November 2018
Transcript of Neither Wolf nor Dog: P-Management in a Quasi-Polymictic Lake€¦ · Kieser & Associates and...
TEMPLATE DESIGN © 2008
www.PosterPresentations.com
Neither Wolf nor Dog: P-Management in a Quasi-Polymictic Lake
Introduction
Drowned river mouth lakes are common along the western shore of Lake Michigan. Hydrodynamically linked to the larger system, these small lakes receive intrusions of colder, cleaner water that impact thermal stratification (e.g. vertical mixing) and biogeochemical (e.g. sediment phosphorus flux) processes.
Mona Lake (MI) has historically received wastewater effluent leading to its present eutrophic state. Wastewater diversion, implemented in 1972, has failed to improve trophic state conditions and the lake continues to experience hypolimnetic anoxia, elevated phosphorus levels and cyanobacteria blooms, with 2018 peak microcystin concentrations nearing 400 ug/L (DEQ Monitoring). The work reported here tests the hypothesis that water quality conditions in Mona Lake are driven by internal phosphorus loading. The role of the system’s weakly stratifying nature and intrusions from Lake Michigan in mediating recovery are explored.
Study Site Description
Stratification P Transport Trophic State
References
• Length of 6.5 km, average width of 0.5 km• Mean and maximum depths of 4.5 and 11.0 m• Oriented east-west, aligned with strong prevailing westerly
winds over Lake Michigan. • HRT: 105 to 160 days during low tributary flows, less than 35
days during high flows3• Tributaries: ~90 percent of the hydrologic and phosphorus load
enters the lake at its east end5
Mona Lake stratifies ephemerally, i.e. exhibits metastable polymixis, driven by strong winds traveling parallel to its major axis. The system alternates between a thermally stratified state with oxygen depletion and soluble reactive phosphorus accumulation in the hypolimnion and a completely mixed state where oxygen is re-introduced to bottom water and phosphorus is transported to surface waters.
• Seiches and surges from Lake Michigan can change water chemistry, stratification.
• Hypothesis: colder migrant water increases the resistance to mixing, strengthens hypolimnion.
Intrusions
Current Conclusions
Modeling
Both intrusions and mixing events can be observed in hypolimnetic temperature variances during the ice-free sampling season.
While Mona Lake has spatial differences in stratification regimes, vertical profiles showed heterogeneity-at-depth between sites, and thus, a 1D mass-balance modeling platform (LAKE2K)2 is to be used to simulate physical and biogeochemical processes as a means to:
• Identify maximum achievable external load-based trophic state • Testing external load reduction strategies • Quantify diffusion-based P transport4
Upon completion of further model confirmation and calibration, hypothetical loading scenarios are intended to form the basis for remedial and management action plans. Field data and empirical models support the hypothesis that Mona Lake is capable of assimilating it’s current external load – but trophic state improvements will not be made manifest until internal loading is addressed.
Based on 2017 and 2018 field data, approximately 30 percent of Mona Lake possess a depth capable of stratification strong enough to result in anoxia, found to be ~6m. Thus, application of engineering approach management solutions may need only be present in a small area of the lake bottom, making some often cost-prohibitive approaches feasible.
Beyond the established deliverables of this research, it aims to serve in increasing the understanding of other shallow, dynamic systems and how best they are managed.
Figure 1. Mona Lake Watershed Area (Annis Water Resources Institute)
Figure 2. Bathymetry, with imposed basins based on relative mean depth bins.
Figure 3. Continuous temperature monitoring at a single deep site.
Figure 4. Intrusion detection through conductivity profiles at westernmost field sites.
Figure 5. Hypolimnetic temperature variances between sampling dates (2018).
[1] Carlson, R. (1977). A trophic state index for lakes. Limnology and Oceanography 22. [2] Chapra, S., and Martin, J. (2004). LAKE2K: A Modeling Framework for Simulating Lake Water Quality (Version 1.2): Documentation and Users Manual. Civil and Environmental Engineering Dept., Tufts University, Medford, MA.[3] Evans, E. (1992). Mona, White, and Muskegon Lakes in Muskegon County, Michigan: the 1950s to the 1980s. Michigan Department of Natural Resources, Lansing, MI. MI/DNR/SWQ-92/261.[4] Limno-Tech. (1982). The Effect of Wastewater Land Treatment on Eutrophication in Muskegon County Lakes.[5] Steinman, A., Rediske, R., Denning, R., Nemeth, L., Chu, X., Uzarski, D., Luttenton, M. (2006). An environmental assessment of an impacted, urbanized watershed: the Mona Lake Watershed, Michigan. Arch. Hydrobiol., 166.
Major TurnoverMinor Major
IntrusionIntrusion
Wastewater diversion reduced the external phosphorus loading to Mona Lake by 75-80 percent from 1972 to 19814. Analysis of changes in external phosphorus loading according to the Vollenweider (1975) model predicts a transition in trophic state from eutrophic (pre-diversion) to near mesotrophy (post-diversion).
Water Quality
Internal Loading
Field measurements made in this study provide clear evidence of sediment-P release to hypolimnetic waters (rates of 10-12 mgP m-2
d-1) for the 30 days of anoxia occurring irregularly over the summer season. Increases in phosphorus levels in the epilimnion, an important trigger for algal blooms, are likely ascribable to wind-driven mixing events as tributary discharges are modest (at best) during summer and diffusive vertical mass transport is not of a sufficient magnitude to account for the rate of increase observed.
Figures 6 and 7. Vollenweider (1975) loading plot and Carlson (1977) TSI.
Figures 8 and 9. 2017 TP concentrations at deep sites and whole lake.
Application of a trophic state index (TSI)1 based on field measurements of water column conditions suggest minimal improvement occurred in response to wastewater diversion. This forms the basis of our hypothesis that internal loads govern trophic state conditions in the post-diversion period.
Upwellings of highly bioavailable phosphorus-rich water, driven by vertical mixing events, lead to discernible increases in surface water phosphorus. Chlorophyll and microcystin observations (MDEQ 2018) correlate well to the increase in phosphorus concentration.
Figure 10. Observed TP concentrations , MDEQ chlorophyll and microcystin detection for 2018.
Acknowledgements: George Cannon Scholarship, Mona Lake Watershed Council,
Kieser & Associates and Michelle Storey (MDEQ)
Hayden Henderson and Dr. Martin T. AuerGreat Lakes Research Center at Michigan
Technological University
Presented at the 38th International Symposium of the North American Lake Management Society, Cincinnati, Ohio - October 30-2 November 2018
