1. Bahram Khazaei, Hector Bravo, and Harvey Bootsma
MODELING THE TRANSPORT AND FATE OF PHOSPHORUS FROM A POINT SOURCE IN THE LAKE MICHIGAN NEARSHORE ZONE
Bahram Khazaei, Hector Bravo, and Harvey Bootsma
Poster Competition University of Wisconsin-Milwaukee
April 8, 2017

2. Research Motivation & Objectives
Nutrient loading into Lake Michigan can produce:
algal blooms,
hypoxia,
beach closures,
clogging of water intakes, and
reduced water quality

3. Materials & Methods
A 3D nested model were applied to determine the influence of MMSD SSWWTP phosphorus loading:
the coastal area of interest is simulated by the nested model,
a grid size of 100m, 120x445 cells in the cross- shore and alongshore directions, and
20 equally-spaced sigma layers
simulations were focused on the time of year for Cladophora growth, detachment, and shoreline fouling (June-October)

4. Materials & Methods
The 3D model consists of a hydrodynamic model linked with a biogeochemical model:
hydrodynamic component: National Oceanic and Atmospheric Administration (NOAA) Lake Michigan model of the Great Lakes Coastal Forecasting System (GLCFS) based on the Princeton Ocean Model (POM)
biogeochemical component: a mussel model, a Cladophora model, and a sediment dynamics model are linked

5. Results: DP and PP Comparison
Loading patterns were different in 2013 and 2015, especially in July and September. This can be related to different:
rainfall patterns,
water consumption, or
wastewater treatment practices
MMSD Outfall Location

6. Results: DP and PP Comparison
Simulations of DP and PP showed reasonably good agreement with measurements
DP shows more fluctuations and variability in 2015
PP showed a smaller range of variation than that of DP, however, more frequent spikes of concentration in 2013 were observed, due to resuspension events:
It can be explained by the meteorological variability of the study area, with stronger winds in 2013
Atwater Station: DP
Atwater Station: PP

7. Atwater Station: Cladophora Atwater Station: Temperature
Results: Cladophora
Seasonal trends in Cladophora biomass were similar in 2013 and 2015, however, the biomass is significantly higher in The reasons could be:
interaction with higher DP concentration in water, and
reduced temperature due to climate variability
Atwater Station: Cladophora
Atwater Station: Temperature

8. Results: Assimilative Capacity
Assimilative Capacity: difference between the total phosphorus target of 7 µg/L and the lake background concentration
Limit loading rate: the loading rate that, when diluted over the control volume reaches the assimilative capacity, on average over the averaging period
A process-based control volume can be defined using the maps of spatial distribution of total phosphorus criterion exceedance, with contour lines of percentage of time that the criterion is exceeded during the summer season
Total volumes and areas of lake’s water affected by TP higher than 7 μg/L more than 25% of the time

9. Results: Footprints of exceedance of TP target concentration
2013
2015

10. This is what we are trying to accomplish!
Summary
Simulations are reasonably in good agreement with measurements
Different loading patterns in 2013 and could be explained by climate variability and human interventions
DP shows more variability in 2015 due to algal bloom
PP showed spikes of concentration in were observed, due to frequent resuspension events, comes from meteorological variability
Cladophora biomass increased in due to higher DP concentration in water, and climate variability
This is what we are trying to accomplish!
Questions?