How healthy is Michigan’s longest river?
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EmailGrand River in the spotlight at Tenth Annual Water Quality Forum.
For the past ten years, attendees at the annual Ottawa County Water Quality Forum have heard from researchers on a variety of topics ranging from E. coli and beach closures to emerging issues such as pharmaceutical contamination. The Grand River has often been the focus of questions related to water quality, but do we really know how healthy the Grand River is?
The question is a tricky one because the concept of “health” has many components. For example, a person might be running a fever of 103˚F but be healthy in terms of blood pressure and cholesterol. Looking at a single measure of health may be equally misleading when dealing with environmental health.
A presentation from Michigan Sea Grant and Michigan State University Extension kicked off the forum on Nov. 13, 2015, by addressing the many aspects of water quality and other components of ecological health in rivers. Water quality measures related to physical, chemical, and biological properties are often interrelated. For example, temperature affects the amount of oxygen dissolved in water, which in turn affects the microbes that live in water. Nutrient availability also affects microbial activity, and high levels of phosphorus lead to high biochemical oxygen demand and low dissolved oxygen.
Other components of ecological health in rivers include watershed characteristics such as land use patterns and nutrient sources. Land use, along with soil types, also affect hydrology or the “flashiness” of streams. Flashy streams tend to flow very little during droughts but flood quickly during heavy rains.
The Grand River is not as flashy as some streams in the Saginaw River watershed, but is it is more flashy than the Muskegon River and many northern Lower Peninsula rivers with more forested watersheds and sandier soil. Nutrient sources were also high in the lower Grand River watershed relative to most other Michigan watershed according to a recent study, although some Saginaw Bay and thumb area watersheds were higher.
As for water quality, the city of Grand Rapids has monitored water quality since 1985 using a Modified Water Quality Index. This index does not provide for direct comparison to other rivers, but measurements taken upstream and downstream of the city show a trend of improving water quality over time. The index also shows only a slight decrease in water quality downstream of Grand Rapids, with all values in recent years indicating “Good” water quality and very few limits to recreational use.
Biological communities are often used as indicators of ecosystem health because rivers change dramatically based on precipitation and season. Organisms like fish, and especially invertebrates, must tolerate changing conditions through time. Finding sensitive species in a river therefore indicates relatively good water quality through time while abundant “tolerant” species tends to indicate water quality problems.
The Michigan DEQ found that bottom-dwelling invertebrates in Ottawa County waters of the Grand River were rated “Poor” in 2009. A more comprehensive research paper published in 2010 classified 38.6 percent of river miles in the Grand watershed as “impaired” based on fish and invertebrate communities. In comparison to 31 other Michigan watersheds, the Grand River watershed ranked as the 9th most impaired.
In terms of fecal contamination, a 2012 study found that human sewage is not a major contributor of Bacteroides and other fecal coliforms such as E. coli. Grand Rapids has done much to remedy past problems with Combined Sewer Overflows (CSOs), but it should be noted that 2012 was a low water year.
More details on Grand River health are given in the full presentation, and presentations from the past decade of Ottawa County Water Quality Forums can be found at miottawa.org.
Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.
