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  • Terry Gronwall

Monday July 19th 2021 Honeoye Lake Water Quality

Surface Water Temperature: 77.9 F

Water Clarity: 3.3 Feet

Lake Level: 804.1 Feet above sea level

Lake Level Relative to Weir: +0.6 Feet

Observations: Monday (7/19/21), The water clarity has decreased by ~7 feet over the last week, due to last Saturday’s rain storm, to 3.3 feet and the surface water temperature has increased 2.5 degrees Fahrenheit to 77.9 Fahrenheit. There was light Gloeotrichia, an early season blue-green algae species, visible in the water column in most areas of the lake this morning. We did not see any Gleoetrichia surface scum. For more information on Gloeotrichia see the articles at HARMFUL ALGAL BLOOMS | Honeoye Lake (

The DEC recommends that you, your family, and pets avoid contact with water that contains blue-green algae bloom like Gloeotrichia. Everyone should be very careful to watch for blue-green algae blooms for the next few weeks.

Last Saturday we got ~4.5 inches of rain. Lake level rose about one (1) foot during this storm. We have not had a rain event of this magnitude since the three 5–6-inch rain events in 2014 & 2015. This storm water run-off brought a lot of sediment and nutrients into the lake. This external load of nutrients could potentially fuel a blue-green algae bloom over the next few weeks.

This storm also deposited a lot of shale, dead trees, and other floating debris into the lake. Be very carefully when boating on the lake over the next week or so. Many culverts plugged on County Road 36 and East Lake Road causing temporary road closures to allow the town and county highway departments to clear this debris off the road. Private property owners also had shale and dead trees deposited on their property.

Today, July 19th, the lake remains stratified releasing legacy phosphorus from the bottom sediments all over again. When a lake stratifies and forms a thermocline the decaying organic matter, dead algae and weed fragments, on the lake bottom consumes dissolved oxygen in the water below the thermocline. When the dissolved oxygen has been completely consumed the phosphorus iron bond in the bottom sediments becomes weak releasing legacy phosphorus into the water near the bottom sediments. See dissolved oxygen chart 8-9 m to the left.

Always use your own visual assessment before making contact with the lake water at this time of year as the blue-green algae situation can change daily if not hourly. Please regularly check the DEC HABs alert map for more detailed updates on Honeoye Lake HABs alerts:

Click on the blue outlined box that says "Log in / Sign up" in the upper right hand corner of this page to sign-up to be notified when we update our weekly Honeoye Lake water quality blog.


- Click on this link for "2021 Honeoye Lake Aeration Engineering Planning Project"

- The NYSDEC has recently released a new report “Feasibility Assessment of Harmful Algal Bloom Management Options for Honeoye Lake and Conesus Lake” as a follow-up to their 2018 Honeoye and Conesus Lake HABs Action Plans. Click on the link SCIENTIFIC RESEARCH | Honeoye Lake ( to see report:

This report evaluates various techniques for mitigating Harmful Algae Blooms in Honeoye Lake by preventing the release of legacy phosphorus from the lake bottom sediments.

- Click on this link for HLWTF Winter newsletter: e6fc30_ef8d01223f42408ba11b3a7a5f83bebe.pdf

- Click on this link for "2020 Water Quality: What, Why, What's Next"

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