Skip to main content

Water Quality Issues


We measureĀ E. coli, a type of bacteria that can be found naturally in the environment, as an indicator of possible fecal contamination. While E. coliĀ is often harmless, persistently high levels can indicate fecal pollution and an increased risk of illness when recreating in a waterbody. Learn more in the E. coli Fact Sheet (Spanish).

Potential Sources:

  • Pets
  • Trash and urban wildlife
  • Livestock
  • Faulty sewers and septic systems


Nutrients, such as nitrogen and phosphorus, occur naturally in the environment and are important for healthy aquatic systems. Human activities contribute excess nutrients to waterbodies that can lead to harmful algae growth, reducing oxygen for aquatic life and sometimes producing harmful toxins.

Potential Sources:

  • Fertilizers
  • Detergents
  • Pets, urban wildlife, and livestock
  • Faulty sewers and septic systems
  • Treated wastewater


Certain metals can impact drinking water quality or be toxic to aquatic life when there are high concentrations in our waterbodies. Metals are naturally occurring in our environment, but human activities can contribute excess metals that become a water quality issue.

Potential Sources:

  • Active and legacy mines
  • Soil erosion and rock weathering
  • Road salts and urban runoff
  • Various industrial sources