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Tribal Programs in the Pacific Southwest

Understanding Key Water Quality Indicators in EPA's Pacific Southwest (Region 9)

This page contains a collection of fact sheets about key water quality indicators. These were produced in Region 9, but contain useful information for any area.

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  • Dissolved Oxygen Fact Sheet (Region 9) (PDF)(1 pg, 110 K, 07/16/2009)
    Information about Dissolved Oxygen, which serves as an indicator of the biological health of a water body, and the importance of having enough data to adequately determine trends and/or compliance with tribal, state, or federal standards.
  • pH Fact Sheet (Region 9) (PDF)(1 pg, 231 K, 7/16/2009)
    pH is a measurement of acidity or alkalinity and affects many chemical and biological processes in a water body. Most aquatic organisms prefer a neutral pH range of 6.5 - 8.5. Changes in pH can be caused by a variety of factors, including: acid rain, mining activities, and wastewater discharges.
  • Temperature Fact Sheet (Region 9) (PDF)(1 pg, 113 K, 7/16/2009)
    Temperature is an important indicator of the general condition of a water body and the ecosystem it supports.
  • Turbidity Fact Sheet (Region 9) (PDF)(1 pg, 122 K, 7/16/2009)
    Turbidity is a measure of the clarity of a water body and is related to erosion and sedimentation which impacts streams and lakes.
  • Total Phosphorus Fact Sheet (Region 9) (PDF)(1 pg, 163 K, 7/16/2009)
    Total Phosphorus is an essential nutrient for plants and animals. It is naturally limited in most fresh water systems because it is not as abundant as carbon and nitrogen; introducing a small amount of additional phosphorus into a waterway can have adverse effects.
  • Total Nitrogen Fact Sheet (Region 9) (PDF)(1 pg, 286 K, 7/16/2009)
    Total Nitrogen is an essential nutrient for plants and animals. However, an excess amount of nitrogen in a waterway may lead to low levels of dissolved oxygen and negatively alter various plant life and organisms.
  • E. coli Fact Sheet (Region 9) (PDF)(1 pg, 140 K, 2013)
    E. coli and enterococci levels are used as indicators of the presence of fecal material in drinking and recreational waters. Both indicate the possible presence of disease-causing bacteria, viruses, and protozoans. Such pathogens may pose health risks to people fishing and swimming in a water body.