What
are Impaired Waters? *
Every two years, the Clean Water Act requires states to publish an updated
list of streams and lakes that are not meeting their designated uses because
of excess pollutants. The list, known as the 303(d) list, is based on violations
of water quality standards and is organized by river basin.
What are TMDLs?
A newly invigorated approach to help solve the old problem of water pollution
is developing Total Maximum Daily Loads (TMDLs). The federal Clean Water Act
requires states to adopt water quality standards to protect the nation’s
waters. These standards define how much of a pollutant can be in a surface
and/or ground water while still allowing it to meet its designated uses, such
as for drinking water, fishing, swimming, irrigation or industrial purposes.
Many of Minnesota’s water resources cannot currently meet their designated
uses because of pollution problems from a combination of point and nonpoint
sources.
For each pollutant that causes a water body to fail to meet state water quality
standards, the federal Clean Water Act requires the MPCA to conduct a TMDL
study. A TMDL study identifies both point and nonpoint sources of each pollutant
that fails to meet water quality standards. Water quality sampling and computer
modeling determine how much each pollutant source must reduce its contribution
to assure the water quality standard is met. Rivers and streams may have several
TMDLs, each one determining the limit for a different pollutant.
2002
303(d) List
In the Minnesota River Basin, there are 29 rivers and creeks that are impaired
for one or more of the following pollutants: Low Dissolved Oxygen, impaired
biota, mercury, fecal coliform, turbidity, excess ammonia, Chloride, PCBs,
and eutrophication. The Minnesota River has the most reaches listed for impariment
in the Basin - 46. There are also 81 lakes listed with one or more of the
following impairments: excess nutrients and mercury or PCBs in the water column
and/or fish tissue. Altogether, there are 320 river reaches and lakes listed
as imparied in the Basin.
*Text courtesy of Minnesota Pollution Control Agency (MPCA)
FOR MORE INFORMATION
MPCA's Total Maximum Daily
Loads and Minnesota's Waterways
http://www.pca.state.mn.us/water/tmdl.html
MPCA's Minnesota River Basin
http://www.pca.state.mn.us/water/basins/mnriver/index.html