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Monitoring The Lake's Water Quality

2017 Update

In 2006, Dorothy Jamison took over the primary responsibility for testing for lake water transparency.

YEAR Average Transparency
Depth in feet
Carlson Ratio
Carlson Ratio
2014 13.9 39 11 39
2013 14.8 38 8


2012 14.7 38 - -
2011 15.7 ? 11 39
2010 17.5 36 9 36
2009 17 36 14 42
2008 12.8 40 14 42
2007 17.1 36 12 40
2006 21.3 33 8 34
2005 18.8 35 7 35
2004 19.97 35 5 28
2003 18.2 35 - -
2002 18.9 35 15 43
2001 13 40 10 37
2000 14.2 39 - -

For more information on the lake water monitoring program in Michigan and to access data on Gratiot and other inland lakes go to:
Michigan Department of Environmental Quality (MDEQ) Inland Lakes web page
Michigan Clean Water Corps: micorps.net

Larry Anderson and Ian McPherson are scientists and GLC supporters who have been discussing with Bonnie various ways in which GLC might gather additonal data to monitor Lake quality and factors which may have an impact upon it. Larry has gathered and charted various Gratiot Lake data gathered over time from a number of sources. This data will be used to determine what data might be most useful to gather beyond the transparency and phosphorus readings GLC currently gathers.

Click on this chart to open slides of all of the data Larry has charted.

2004 Update

In 2004, Al Hochstein did transparency testing from May through September. Below is a summary of five years of volunteer water quality monitoring at Gratiot Lake. Some variation from year to year is expected due to factors such as lake level and weather. Gratiot Lake transparency readings indicate that there is not an overabundance of algae or a lot of suspended solids such as silt in the water tested. The 2004 phosphorus reading is lower than previous readings. Since phosphorus can be an indicator of polluted runoff from failing septic systems or fertilizer runoff, lower levels are considered better.

Taken with other data collected from time to time by the Michigan Department of Environmental Quality (MDEQ) this data indicates that Gratiot is a healthy lake capable of supporting a broad spectrum of aquatic life. This data gives a picture of the lake’s status from year to year and the Carlson Ratio can be used to compare it to other lakes.

Thanks to Al and Carol Hochstein who have helped GLC in many ways in addition to water monitoring—from trail map box building to gutter installation for the rain barrel!

Water Monitoring Information
2000 - 2003

The Conservancy is a member of Michigan Lakes and Streams Association (ML&SA). ML&SA’s goals are to assist lake, river, and watershed associations in the management of waterfront property and to prevent degradation and pollution of surface waters.

ML&SA members keep tabs on surface water quality throughout Michigan through the Cooperative Lake Monitoring Program (CLMP). CLMP is a partnership of the
Michigan Department of Environmental Quality Inland Lakes Monitoring and the ML&SA. Volunteers monitor water quality and note changes over time to assist lake, river, and watershed organizations in the management of waterfront property. CLMP is also a cost effective way for the MDEQ to compile baseline data on lake water quality.

Volunteers perform weekly tests from May until September to determine the clarity/turbidity of the water and its phosphorus content. Only a few Upper Peninsula groups are involved in the program. Ed Kaeding is taking weekly readings by submerging a black and white disk into the water and viewing the point at which it is no longer visible. These secchi disk readings track the clarity of the water. Ed also samples phosphorus levels in Gratiot. Phosphorus can influence the growth of algae in the water.

The data collected serve as indicators of the water quality of the lake and provide a point from which to view changes in the lake over time.

Ed's original data from weekly (June through September 2000) secchi disk monitoring showed the depth at which the disk was visible varied from 11’ to 18’8”. The depths were generally the greatest in June and July and the least in August and September. Historically, the occasional secchi sampling done by the DNR had shown depths from 15’ to 20’ which is considered deep for Michigan lakes.

This reading along with measures of phosphorus in the water classify Gratiot as oligo-mesotrophic. According to the DEQ “oligotrophic lakes are generally clear, deep, and free of weeds or large blooms of algae.” Although available nutrients are generally low in oligotrophic lakes “a food chain capable of supporting large game fish” is often developed. Mesotrophic lakes have more nutrients in the water which can result in the growth of more vegetation including algae. In this more “productive” type of lake, lack of oxygen near the bottom may adversely affect cold water fish. Northern pike and walleye are usually the dominant fish in mesotrophic lakes.

2001 Water Sampling for Gratiot Lake
Indicates Good Water Quality

Results of 2001 Cooperative Lakes Monitoring Program (CLMP) indicate that Gratiot Lake ranks well on the two measures taken but may have room for improvement.

In the secchi test a black and white disc is lowered into the lake to measure turbidity, this indicates the amount of sediment or algae in the water. This measurement is taken weekly mid-May to mid-September. In reports from 184 Michigan lakes measurements from 1.4 - 62 feet were recorded. The average for the state was 12.2 feet. Gratiot fluctuated between 8.7 feet and 16 feet with an average of 13 feet. Historically, readings from Gratiot taken in 1975 and 1988 by the State averaged 15-20 feet. Current readings indicate that Gratiot is a healthy lake with some periods of algal “blooms” which may indicate some pollution from fertilizers, leaky septic systems, or sediment runoff into the water.

In 2001, for the first time a summer phosphorus reading was taken in August. A high phosphorus reading may indicate fertilizer runoff or faulty septic leakage that can cause over production of algae in lake water. The 150 Michigan Lakes which measured summer phosphorus in 2001 ranged from <5 to 95 ug/L with an average of 14 ug/L. Gratiot was on the low side with 10 ug/L which is a very good reading indicating a healthy lake.

The CLMP protocal required that these readings be taken in the area where the lake is deepest. Sampling nearer to an area where homes are concentrated might yield a different result.

Thanks again to Ed Kaeding who has been steadfast in looking into the water and taking measurements.

Contact GLC Program Director: director@gratiotlakeconservancy.org
(Please put "Gratiot Lake" in subject line.)