Lake Level- 12/6/07:  686.85

Desired Level:                 687.22

The current lake level is 0.37 feet below the guide curve [see chart below] for this time of year.  We have experienced a significant drought from late spring through the fall.  Recent precipitation and reduced evaporation is starting to bring the lake level closer to the guide curve.  The City is releasing the minimum flows out the feeder canal. 

The lake level is controlled by a variety of factors including precipitation, watershed size, outlet control by the City of Canandaigua, water supply withdrawal and evaporation.  The guide curve was established to try and maintain the multiple uses of the lake for all its inhabitants throughout the year.  Some of those uses include water supply for over 60,000 people, recreational boating, fishing, and maintaining the Hi-Tor wetland system. 

To better understand the various influences on lake level, a summary of each is provided below: 

Precipitation:

This region including the lake surface annually receives approximately 31 inches of precipitation a year.  The City of Canandaigua’s Water Treatment Plant personnel record daily precipitation to the hundredth of an inch.  Precipitation impacts lake level not only in its amount but also in its timing. 

Total: 9.3 billion gallons per year (2.6 feet of lake surface)  

Watershed Size:

Because water runs down hill, the amount of land area (watershed) contributing to a water body increases the amount of water in the lake.  Canandaigua’s watershed (land area the drains to the lake) is 174 square miles extending along either side of the lake down through Naples.  The watershed is approximately 11.5 times the size of the lake area.  On an annual basis approximately 1/3 of the 31 inches of precipitation that lands in the watershed ends up as streamflow entering the lake.  The other 2/3 evaporates, is used by plants or goes to the deep groundwater.  This ratio changes throughout the year and is also impacted by the intensity of an individual storm.  Over an entire year based on rough approximations 34 billion gallons of water enter the lake via the streams.  34 billion gallons is equivalent to 9.5 feet across the surface of the lake. 

Total: 34 billion gallons per year (9.5 feet of lake surface) 

Outlets:

The two outlets are controlled by the City of Canandaigua.  The State of New York granted the City control over the level of the lake in 1886.  The smaller gate is the outlet to the feeder canal to dilute the treated water coming from the Sewage Treatment Plant.  The City is required to maintain a minimum flow of 35 cubic feet per second (cfs) to meet state imposed water quality standards.  This flow equals 22.6 million gallons per day or 8.2 billion gallons a year.  This is equivalent to 2.5 feet of lake surface.  This flow is necessary not only for the City’s Sewage Treatment Plant, but also for other wastewater plants along the outlet. 

Total Feeder Canal:   8.2 billion gallons per year (2.25 feet of lake surface)

The second gate system is on the natural outlet and is opened and closed based on lake levels.  With this gate system fully open the lake can be drained by approximately one inch/day (300 million gallons).  These gates were open for much of the spring season due to high lake levels.  Because the outlets can only lower the lake by one inch a day, the City constantly needs to watch the weather forecasts for the “big storm”.

Water withdrawal:

New York State has issued five separate water withdrawal permits to the following municipalities:

Ø      City of Canandaigua:             6.0 Million Gallons per Day

Ø      Town of Gorham:                    1.5 Million Gallons per Day

Ø      Village of Newark:                   4.0 Million Gallons per Day

Ø      Village of Palmyra:                  3.0 Million Gallons per Day

Ø      Village of Rushville                 0.96 Million Gallons per Day

Only on the dog days of summer do these municipalities come close to their permitted withdrawals.  2003 withdrawals showed that only 3.3 billion gallons of water of the 5.6 billion gallons permitted were taken out over the entire year.  3.3 billion gallons is equivalent to 11 inches of lake surface.  If one of the five water purveyors increased their daily water withdrawal by 1 million gallons a day that would only reduce the lake surface by 1.2 inches over the entire year! 

Total: 3.3 billion gallons per year (11 inches of lake surface)

Evaporation:

Annual evaporation rates are approximations based on experiments.  It would be nearly impossible to accurately measure to an inch of lake water, how much evaporation takes place across Canandaigua Lake.  Many variables change this average substantially.  For our region it is estimated that roughly two feet of lake surface is evaporated on an annual basis.  Most of this evaporation occurs during the summer months.

Total:  7.2 billion gallons per year (2 feet of lake surface)

Summary:

There are obviously many influences on lake level across the year.  The biggest influences (precipitation, watershed size, and evaporation) are completely out of human control.  Human influences, (sewage dilution, water supply) have less of an impact on lake level.  Proper management of the gates on the natural outlet throughout the year by the City of Canandaigua protects lakeshore residents from flooding and maintains the multiple uses of the lake.  Please take a look at the current lake level as compared to the guide curve and the historical data provided.   

© Canandaigua Lake Watershed Council 2002

This Page Last Updates On: December 06, 2007