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Cyanobacteria on Lake Mendota at the Memorial Union

Cyanobacteria

All five Yahara lakes saw cyanobacteria (blue-green algae) blooms throughout the summer of 2019. One bloom in particular on Lake Mendota was quite large, covering at least an area from Picnic Point to the Memorial Union on August 1st. The bloom was well-documented by photos from community members as having a green pea soup-like consistency.

Cyanobacteria blooms are often bright green, but can also appear in shades of brown, blue, and white. Typically, blooms are spotted on warm days with calm winds. On August 1st, Madison reported a high of 81 degrees with an average wind speed of two miles per hour. 

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2018 Flooding

Yahara Lakes 2018 Water Quality Monitoring Results

Overview

From May to September of 2018, water quality monitoring took place at piers and beaches around the five Yahara lakes. Volunteers measured near-shore water clarity, air and water temperature, and noted several visual observations. Visual observations included presence of algal blooms (green/blue-green), floating plant debris, swimmers, waterfowl, wave intensity, and general water appearance. Volunteers report conditions on our website, Lakeforecast.org. The website displays updated data in real time.

Highlights

  • 79 near-shore and 7 offshore monitoring stations on all five Yahara lakes (Figure 1)
  • Weekly off-shore measurement of Secchi depth on all five lakes
  • Measured temperature and dissolved oxygen profiles on all five lakes (seven sites total)
  • Weekly monitoring continued at all 25 public beaches
  • 44% increase in number of condition reports from 2017 (Table 1)
  • Collected continuous near-shore temperature measurements at 17 sites on lakes Mendota, Monona, and Waubesa, and Kegonsa
  • Implemented E. coli sampling and cyanobacteria toxin testing pilots
  • Averaged 2.3 condition reports per site each week across all sites
  • Continued weekly Weekend Lake Reports with over 77,000 views on social media
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Water Quality Monitoring

2017 monitoring season

What started in 2013 as a handful of Clean Lakes Alliance board members testing the water has now grown into a network of over 70 volunteers doing weekly water quality monitoring on all five lakes.

Each week this summer, our team of monitors gathered data on water clarity and temperature. They also made visual observations on beach conditions and identified potentially harmful cyanobacteria (blue-green algae) blooms. And what a summer it was!

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