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Water Quality Update for August 27, 2021

So far this week:

• 38 surveys performed

• 7 Blooms reported

Welcome to your Friday Water Quality Update!

The good news is that the vast majority of our 10,500 acre lake and 36 miles of shoreline remains free of significant concentrations of blue green algae (cyanobacteria). As of 3:00 PM today (Friday) we have had zero bloom reports. Over the last two weeks, we have done two rounds of testing in 9 locations to look at average levels of blue green algae in the open water and all test results are showing low levels of cyanobacteria that are well below bloom levels. Secchi Disk measurements by staff and volunteers are also showing that our water clarity is holding at about 5.0-5.5 meters on average. The cloudy weather and slight north winds today have reduced any potential for blooms to form. Watershed staff looked at several locations on both the east and west sides of the lake and conditions at these locations looked clear as of 12:00 PM.

However, yesterday (Thursday) proved that conditions can change quickly. Yesterday, we had multiple reports of isolated blooms on the east side of the lake- especially in the Cottage City/Crystal Beach area. Deep Run Beach in Gorham (run by Ontario County) closed yesterday due to some visible concentrations of blue green algae. NYS Department of Health will test the water on Monday to determine if the beach can re-open.

Recent rains and duckweed

We were also reminded this week that the lake is connected to a larger ecosystem and watershed area. The rains of last week raised the level of the lake by about 9 inches. Although the lake surface received about 2 inches of rain on average- the 109,000 acre drainage area contributed the other seven inches of water in the lake. There is about 300 million gallons of water in an inch of lake depth- so approximately 2.1 billion gallons of water flowed into the lake from the surrounding watershed! The main outlet gates have been opened since the storms of last week and the lake level has been lowered by about 4.5 inches to 688.75 feet above sea level.

The southern half of the watershed, especially the Naples and Middlesex/Italy area had closer to 4 inches of rain. We had significant flooding in the Naples Creek watershed. The stream flow from Naples Creek and the West River ultimately flows through the High Tor wetland system. This wetland system supports a tremendous amount of duckweed and watermeal (harmless tiny aquatic plants) as part of this ecosystem. The major streamflows pushed much of this duckweed and watermeal into the lake. Within a week, we have seen these visually imposing floating mats make their way to the north end of the lake - 15 miles!

Duckweed and watermeal are harmless tiny floating aquatic plants that grow in the High Tor wetland system and are an important part of this ecosystem. However, many other items including debris and blue green algae can sometimes get caught up in these dense mats of duckweed, so please use caution if boating or swimming in them.

As we move into the weekend, if the hot weather combines with sunny/calm conditions, we can expect isolated blooms of blue green algae (cyanobacteria) to occur. If you notice discolored water, streaking, or surface scums - please avoid these areas. Conditions can change quickly so please use your visual indicators before going in the water. Look for signs of concentrations of algae. As recommended by the DEC, if you see it, avoid it.

If you have a question on a suspected bloom, please feel free to send in a photograph to This email address is monitored by CLWA and Canandaigua Lake Watershed Council staff. We may be able to assist with identification though a clear photograph.

Volunteers and watershed staff will be continuing daily observations throughout August and September and we will communicate any significant changes in bloom activity through our weekly email updates, on our websites, and on the Association's facebook page.

Enjoy your weekend!


More Information on Blue Green Algae

Click below for our Harmful Algae Bloom brochure.

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