The Huron River:"Urban Nonpoint Pollution"
The Huron River is inseparable from the land through which it flows. How people care for the lands that comprise the Huron River watershed greatly influences the health of this river system. The Huron River flows clear and cool in its marsh-dominated headwaters. Streamside vegetation shades the water from the warm sun, provides nourishment for aquatic insects, and prevents erosion. There are few cities in the upper reaches of the watershed.
Through its midreach, the Huron River becomes a chain-of-lakes near Hamburg. As it flows past Dexter, the river is still relatively clear, the water quality relatively good.
When the Huron River reaches Ann Arbor, its nature changes; this is the beginning of the lower reaches of the river. The water quality of the river decreases as it flows past Ann Arbor and Ypsilanti through impoundment after impoundment.
Why the somewhat abrupt change in water quality? Although many people have labeled the Huron River "the cleanest urban river in Michigan" there is still room for improvement.
The primary obstacle to better water quality in the Huron River is the cumulative effect of "nonpoint source pollution". "Nonpoint" refers to the pervasive nature of this pollution that arises from many sources. It is unlike "point source pollution" which is a single identifiable discharge point, usually from industries and wastewater treatment plants.
Let's explore nonpoint source pollution as a consequence of urbanization and the implications of this type of pollution to the Huron River.
Urbanization is a change in land use from generally extensive, open uses (agricultural) to more intensive uses (residential, commercial, and industrial). Major characteristics of urbanization include: (a) conversion of permeable land to impermeable surfaces (concrete, roofs, asphalt), (b) construction of a drainage system (storm sewer) to handle increased stormwater run off, (c) enclosure of natural creeks and their transformation into storm drains (Allen Drain), (d) removal of natural riverbank vegetation, (e) development of flood plains, (f) increased construction, and (g) greater concentrations of people, their cars, their homes, and thereby, a greater concentration of pollutants.
The implications of urbanization for the health of the Huron River can be understood under the following conditions: nutrient enrichment, sedimentation, bacterial contaminations, and heavy metal and toxic compounds contamination.
Implications of Urban Nonpoint Pollution
Nutrient Enrichment: Nutrients, like nitrogen and phosphorus, enter rivers and lakes via rain and melting snow. These nutrients originate from overapplication of fertilizers to lawns, golf courses, and urban parks, leachings from leaves and grass clippings, urban wildlife and pet wastes, illicit sanitary connections into untreated stormwater systems, and poorly functioning on-site septic systems.
Nitrogen and phosphorus stimulate rooted aquatic plant and algal growth. Too much phosphorus can lead to profuse algal growth, called an algal bloom, which colors water a pea-soup green. Algal blooms usually occur in the spring and fall and afflict some of the river lakes near Hamburg and Belleville Lake. Dead algae is fed upon by bacteria that also consume dissolved oxygen during decomposition, thereby robbing dissolved oxygen needed by aquatic invertebrates and fish. Recreational activities, such as swimming, fishing and waterskiing are restricted in waters thick with aquatic plants and/or algae. Some algae can also impart an unpleasant taste and odor to water, restricting its use as a source of drinking water.
Sedimentation: Sedimentation refers to two physical events related to urban runoff. These are: deposition of sediments and particulate suspension. Sediment refers to dirt, silt and organic particles (small pieces of leaves and other debris). Heavy metals (lead, zinc, chrome, etc.) and fecal coliform bacteria may be attached to these organic particles. Sediment comes from urban runoff carrying dirt and heavy metals from streets and parking areas, construction sites and combined sewer overflows.
Deposition of sediments smothers the eggs of fish, aquatic insects and their homes among the rocks, mollusks and attached algae. A rainstorm monitored in August 1979 discharged 212,000 pounds of sediments from five storm drains in Ann Arbor into Geddes Pond on the Huron River.
Sedimentation is an even greater problem in impoundments and results in loss of storage capacity (increasing the potential for flooding), restricted boat use and required filtering by industries that use water. Sediment particles suspended in water scatter and absorb sunlight needed for photosynthesis by aquatic plants; clog fish gills, thereby weakening fish and reducing their resistance to disease; and act as an abrasive to the shells of clams.
Fecal Coliform Bacteria: Fecal coliform bacteria are derived from the feces of warm-blooded animals, including humans. These bacteria enter lakes and rivers from many sources, including: stormwater runoff containing pet and wild animal waste; combined sewer overflows; illicit connections of sanitary sewers into storm sewers; and on-site septic systems.
Because fecal coliform bacteria are common and are associated with pathogenic bacteria and viruses in affected individuals, a high fecal coliform level is an indication that risks to human health are also high.
In Ann Arbor, fecal coliform contamination to Geddes Pond from stormwater runoff has been linked to animal wastes and as yet unknown factors that may contribute to bacterial growth in storm drains. Fecal coliform levels of 200 colonies/ 100 ml or above are considered unacceptable for total body contact recreation, like swimming.
Heavy Metals and Toxic Compounds Contamination: Cars are responsible for most of the heavy metal transported by urban runoff. Examples include lead from exhaust (leaded gasoline),zinc from tire wear,iron from vehicle rust, and copper from metal plating and brake lining wear.
Heavy metals are also derived from some commercial and industrial sites, deposition of industrial air pollutants, and pesticide applications around homes, businesses, golf courses and urban parks.
Because of the pervasiveness of heavy metals, it is a more significant problem than many believe. Between August 17 and August 27, 1979, the five storm drains in Ann Arbor discharged 4,620 pounds of iron, 45 pounds of lead and 220 pounds of zinc into the Huron River (NURP Study, 1981). Most of these particles become trapped in bottom sediments. However, biological activity in sediments and changes in water chemistry can lead to re-suspension of heavy metals. Heavy metal contamination can disrupt natural food chains and bio-accumulate in organisms, like fish.
It seems clear that technological solutions alone will not be enough to curb nonpoint pollution. It will ultimately require a change in values as to how we see ourselves in connection with the land.
For more information, contact:
Huron River
Watershed Council
415 W. Washington
Ann Arbor, MI 48103
769-5123