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Water Quality Update for September 24, 2021


For Friday, September 24, 2021

Reports so far this week (Week of Monday, September 20 - Sunday, September 26):

• 18 surveys performed

• 2 Suspicious Blooms

Welcome to the 13th edition of your Friday Water Quality Update! These updates are crafted in partnership with CLWA and the Canandaigua Lake Watershed Council (intermunicipal watershed organization consisting of the fourteen watershed and water purveying municipalities).

Update on HABS Season Thus Far

We are in the final weeks of the Volunteer Shoreline Harmful Algae Bloom Monitoring Program, with the last official reporting date on Sunday, October 3rd for our routine weekly monitoring. All eyes won’t be off the lake, however, as many will continue to provide reports and assessments even after the program has ended - which is a huge testament to the dedication of our CLWA volunteers! In addition, our partners at the Canandaigua Lake Watershed Council will be continuing with their monthly sampling program in partnership with FLCC, as well as their HABs surveillance and sampling at both shoreline and open water locations.

All in all, so far this season has been “milder” in terms of HABs reports as compared to 2020. Even with the addition of 29 volunteers to the program this year (more eyes out there actively looking for and reporting blooms), we have had fewer bloom reports.

Of the samples that have been collected and sent for analysis at the Finger Lakes Institute, so far we have not seen the high values that we have in year’s past of CyanoChlophyll (measurement of blue green algae). We had a few blooms this summer with high values - our highest to date being a bloom reported on July 1st on the west side of the lake (adjacent to the City of Canandaigua Water Treatment Plant) with a blue green algae value of 266.8 micrograms per liter (ug/L). As a reminder, DEC threshold for a confirmed bloom is 25 ug/L. In 2020, we saw some sample values spike to 1,400 ug/L and 2,500 ug/L at the highest!

While this year’s observations are interesting to compare to 2020, we have learned that the HABs situation is uniquely different each year and can be influenced by a variety of factors, including weather and wind speed. Following the activity of our neighboring Finger Lakes, other lakes such as Skaneateles and Owasco have had fairly active bloom seasons. At this point, we do not have scientific reasoning to share as to why some lakes have active HABs seasons and others do not - which is why documenting the occurrence and severity of blooms has become an important activity for many lake associations. As we collect information to share with community members, documenting HABs trends and learning more about the contributing factors to HABs formation is helping the scientific community to better understand the regional shift of increased frequency and severity of bloom events in recent years.

As the program comes to a close in October, we will look to put together a year end summary of our findings to share with the watershed community.

Current Water Quality Status

On to the current status of the lake. We had 2 bloom reports come in yesterday from the east side of the lake in Rushville around the Long’s Point area. A sample was collected and brought to the Finger Lakes Institute in Geneva this morning (9/24), and although results were elevated (18.8 ug/L of blue green algae), they were below the DEC bloom threshold.

Other areas of the lake have been reporting clear conditions. Today’s 15-20 mph winds do not provide the ideal calm conditions for the formation of blooms.

Last Sunday (9/19) was a very calm sunny day, and was our most active day for bloom reports thus far, with 9 HAB reports filed by volunteers. Surface streaking of algae was reported out in the open water in the morning hours, and a sample collected by a volunteer in a dense streak showed results of 123.52 ug/L blue green algae. Additional samples were collected in the open water from areas that were not experiencing such heavy streaking, and those results came back well below the bloom threshold. This reinforces the concept that when areas of surface streaking are observed, they should be avoided.

As September comes to a close, please remember that there is still the potential for isolated blooms to appear, especially when conditions are just right - calm, sunny weather. Please continue to use your visual indicators and look for signs of a HAB before swimming or letting pets into the lake.

The six Canandaigua Lake water purveyors (the City of Canandaigua, the Village of Newark, the Village of Palmyra, the Village of Rushville, the Town of Gorham, and Bristol Harbour) continue their routine testing of both raw (untreated) and finished (treated) drinking water for microcystin (the toxin that may be produced by cyanobacteria / blue green algae). All results to date have come back as non detects. Results are uploaded weekly on the CLWA website.

As always, we encourage you to follow our reports on our website, and on the facebook page. If you have a question on a suspected bloom, please feel free to send in a photograph to


More Information on Blue Green Algae

Click below for our Harmful Algae Bloom brochure.

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