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River Monitoring

In 1927, the Minnesota and Wisconsin Boards of Health declared the Mississippi River from St. Paul, MN to Prescott, WI a public health hazard, "unfit for use as a source of water supply, for bathing or for boating." At that time, raw sewage and other wastes were discharged directly into the river. It was at that time when a predecessor agency to the Metropolitan Council Environmental Services (MCES) began assessing the water quality of the Mississippi River. The monitoring program has evolved over the years to reflect changing needs and water quality issues.

Today, monitoring allows MCES to:

• measure compliance with state water quality standards and criteria
• meet National Pollutant Discharge Elimination System (NPDES) permit requirements
• assess the performance and effectiveness of MCES wastewater treatment facilities
• determine the biological health of large river ecosystems
• obtain information on the sources and water quality impacts of nonpoint source pollutants
• document long-term trends and changes in water quality
• project future water quality conditions.

The MCES River Monitoring Program is comprised of several sub-programs, including River Water Monitoring, Biological Monitoring, and Riverbed Sediment Monitoring, as described below. In all, more than 150 river miles are monitored on six TCMA rivers: the Mississippi, Minnesota, St. Croix, Rum, Vermillion, and Cannon Rivers.

View the 2006 River Water Quality Summary Report (pdf) for the Twin Cities Metropolitan Area

River Water Monitoring

MCES operates an automatic monitoring network that was initiated in 1973 as a cooperative program with the United States Geological Survey (USGS). The network consists of six monitors which continuously measure dissolved oxygen, temperature, pH and specific conductance of the river water. In addition to the previously listed variables, turbidity is continuously measured at the Fort Snelling site. These variables are good indicators of river water quality and the effectiveness of MCES wastewater treatment plant operations. The data are reported to the Minnesota Pollution Control Agency via monthly monitoring reports, as required by NPDES permits.

Extensive conventional pollutant monitoring is also conducted to complement automatic monitoring. Samples are manually collected at numerous sites in addition to the automatic monitoring stations, and are analyzed for a wide variety of variables not measurable by the automatic monitors. Sample collection takes place on a weekly (March-October) or semi-monthly (November-February) basis at most sites. This sampling schedule may be reduced depending on the variable being monitored. Sample analyses are conducted in the field as well as in the MCES laboratory in St. Paul, MN. The river monitoring results are used to more fully characterize water quality and to help determine specific sources of pollution, as well as the extent and nature of problems that may exist. Monitoring also helps to determine the effectiveness of the MCES Industrial Waste Control (Pretreatment) Program (Industrial Waste & Pollution Prevention Section).

For additional information on river water monitoring site locations, equipment, and variables monitored, check the following link.

• River Water Monitoring

Biological Monitoring

Biological monitoring serves as a useful screening tool for assessing the integrated effects of water pollution on aquatic organisms. Improving or deteriorating trends in water and riverbed sediment quality can be assessed by the composition of aquatic life, since these organisms are greatly affected by the quality of their environment.

Biological monitoring provides information on the presence and abundance of four groups of aquatic organisms: attached algae (periphyton), immature insects, worms and clams (macroinvertebrates), floating algae (phytoplankton) and floating microcrustaceans (zooplankton). Each of these groups represents a different portion of the aquatic community in a river ecosystem.

Biological monitoring is conducted annually during the summer months at 16 sites located on the Mississippi, Minnesota, St. Croix, and Vermillion Rivers. Periphyton sampling is conducted using artificial substrates called periphytometers, which are placed at monitoring sites and allowed to colonize for 14 days. Macroinvertebrate sampling is also conducted using artificial substrates called Hester-Dendy multiple plate samplers, which are placed at the monitoring sites and allowed to colonize for 30 days. Macroinvertebrate samples are also collected via Ponar grab sampling. Phytoplankton sampling is conducted by collecting a composite sample using a Van Dorn water sampler. Zooplankton sampling is conducted using a Wisconsin plankton net, and at some sites using a Clarke-Bumpus plankton sampler. All plankton samplers filter phytoplankton and zooplankton from known volumes of water, allowing their abundance to be calculated (organisms/liter). Taxonomic identification, counts, and diversity index calculations are performed for each of the four biological groups: periphyton, macroinvertebrates, phytoplankton and zooplankton.

For additional information on biological monitoring site locations, equipment, and variables monitored, check the following link.

• Biological Monitoring

Riverbed Sediment Monitoring

Since the passage of the Clean Water Act in 1972, the water quality of our nation's river systems has greatly improved. Riverbed sediment, however, can act as a long-term reservoir for contaminants such as pesticides, herbicides, PCBs, PAHs, and metals. Under certain conditions these contaminants can become more bioavailable, causing direct harm to bottom dwelling (benthic) organisms and leading to bioaccumulation in the aquatic food chain. Riverbed sediments are monitored at selected sites on the Mississippi, Minnesota, and St. Croix Rivers in the TCMA. Historically, MCES riverbed sediment monitoring surveys have been conducted at frequencies ranging from annually (in the 1980's) to decadally (most recent survey concluded in 1998-2001). At each site, samples are collected for toxicity testing, assessing indigenous benthic macroinvertebrate (bottom dwelling insect larvae, worms, snails and clams) populations, and characterizing the physical and chemical make-up of the riverbed sediment. This combination of biological monitoring, toxicity-testing, and chemical monitoring is referred to as the sediment quality triad approach.

Riverbed sediment toxicity testing exposes benthic test organisms to riverbed sediment under controlled laboratory conditions. These toxicity tests are conducted to determine if riverbed sediments have the potential to adversely affect aquatic organisms. The ten-day tests are conducted according to US Environmental Protection Agency sediment test methods using bloodworms (Chironomus tentans) and scuds (Hyalella azteca).

Benthic macroinvertebrates are also sampled at each site and preserved for later identification and determination of abundance. The presence of certain indicator species can provide information about riverbed sediment quality.

Riverbed sediment samples are collected at each site for characterization of physical and chemical composition. Particle size analysis is conducted to determine the sediment grain size composition, and the samples are also analyzed in the MCES laboratory for a variety of chemical constituents.

For additional information on riverbed sediment monitoring site locations, equipment, and variables monitored, check the following link.

• Riverbed Sediment Monitoring

Glossary

Helpful definitions for words located through the Rivers, Streams and Lakes web page.

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