Water Quality of Michigan’s Inland Lakes
	29th April, 2010 - Tony Groves, Pam Tyning, Paul Hausler - Progressive AE

Download Article

Monitoring of select Michigan lakes has been conducted by the Michigan Department of Natural Resources and Environment (MDNRE) since 1973. Currently, as part of Michigan’s Lake Water Quality Assessment Program, the MDNRE and the U.S. Geological Survey (USGS) are jointly monitoring certain Michigan lakes to determine baseline water quality conditions and trophic state. Between 2001 and 2005, 364 inland lakes were sampled. By 2015, all lakes larger than 25 acres with public boat launch sites are proposed to be monitored. These data will then be compared to historical data to evaluate changes in water quality, and to discern differences in water quality in different regions of the state.

Sampling schedule for inland lakes larger than 25 acres. Source: Fuller and Minnerick.1

USGS published a report of findings entitled State and Regional Water-Quality Characteristics and Trophic Conditions of Michigan’s Inland Lakes, 2001-2005. Key findings of the report are summarized as follows:

• About 20% of lakes were oligotrophic, more than 50% were mesotrophic, and about 30% were eutrophic.
• Phosphorus is the nutrient that controls the rate of lake aging or “eutrophication” in most Michigan lakes.
• Total phosphorus and chlorophyll-a levels were lowest and Secchi transparency was greatest in lakes in the northern Lower Peninsula and the Upper Peninsula.
• Specific conductance, a measurement of dissolved solids in water, was generally highest in the southern part of the Lower Peninsula and decreased further north.
• Many lakes in Michigan have high alkalinity. As such, they are able to neutralize acid and buffer the adverse effects of acid rain. However, some lakes, especially in the western Upper Peninsula, have lower alkalinity and are more acidic than lakes in other regions of the state.
• Differences in some of the data collection protocols used over the years make it difficult to definitively compare historical and current lake conditions. However, comparison of some data suggests that about 72% of lakes sampled did not show significant changes in water quality, 18% showed improved water quality, and 11% showed decreased water quality.

References

1. Fuller, L.M., and R.J. Minnerick. 2008. State and regional water-quality characteristics and trophic conditions of Michigan’s inland lakes, 2001–2005. U.S. Geological Survey Scientific Investigations Report 2008–5188, 58p.  Date Posted: December 17, 2008: http://pubs.water.usgs.gov/sir20085188/