> Water > Rivers, Streams, and Lakes Monitoring > Streams Monitoring

Water Quality Variables Analyzed

Metropolitan Council Environmental Services monitors streams in the Twin Cities Metro Area and Mankato Area for a variety of water quality variables (listed on the right). These variables are not always analyzed at all sites all of the time. The variables and sample frequency depends on the sample condition and water quality concern.

Sample Collection

Stream samples are collected on a regular basis during base flow conditions. In the winter, monthly grab samples are obtained. In the spring, summer and fall, sample frequency increases to twice a month. Depending on specific site conditions, additional grab samples might be taken to help further characterize water quality. Along with these base flow grab samples, composite samples are collected by the automatic samplers during storm runoff events. Samples are collected by the automatic sampler on an equal-flow increment (EFI) basis. With EFI sampling, composite samples are collected throughout the event, with discrete sub-samples representing equal volumes of flow.

The photo below shows Equal Flow Increment samples collected from the Le Sueur River in June 2001. The two jars are poured into the bigger plastic jug, to create a "composite" sample. From the big plastic jug, the composite samples are poured into labeled lab bottles. These sample bottles are then transported to the MCES analytical laboratory, which conducts water chemistry analysis on all stream monitoring samples obtained (grab samples and event composite samples).

Stream Water Quality Variables Analyzed

• Temperature
• Dissolved Oxygen
• BOD 5-day
• BOD Ultimate
• CBOD 5-day
• CBOD Ultimate
• Total Organic Carbon
• pH
• Total Alkalinity
• Bicarbonate
• Carbonate
• Fecal Coliform Bacteria
• Turbidity
• Total Suspended Solids
• Volatile Suspended Solids
• Total Dissolved Solids
• Total Kjeldahl Nitrogen
  
• Total Nitrate/Nitrite Nitrogen
• Ammonia Nitrogen
• Total Phosphorus
• Total Dissolved Phosphorus
• Ortho Phosphate
• Chlorophyll-a, Total
• Chlorophyll-a, Pheophytin-corrected
• Conductivity
• Calcium
• Magnesium
• Potassium
• Sodium
• Chloride
• Sulfate
• Hardness
• Metals:
• • Aluminum
  • Cadmium
  • Chromium
  • Copper
  • Iron
  • Lead
  • Manganese
  • Nickel
  • Zinc
• Volatile Organics

(Not all parameters are monitored at all sites)