Water Quality Monitoring Results

Stream Team

For several years the Arroyo Seco Stream Team has been collecting water quality data at various key sites in the Arroyo Seco. These wonderful volunteers are providing an invaluable service because water quality monitoring is a key tool to improve the health of the Arroyo Seco watershed.

The water quality data collected will:

  • Be used in the planning and evaluation of stream enhancement activities;
  • Promote understanding of the overall function of the Arroyo Seco stream;
  • Measure upstream-downstream, seasonal, year-to-year, and long-term changes in water quality and watershed conditions;
  • Detect point sources and non-point sources of pollution;
  • Educate the public about the stream and its riparian corridor; and
  • Develop a sense of community stewardship for the Arroyo Seco and its rich aquatic resources.

Seasonal monitoring is essential for an accurate assessment of the water quality of the Arroyo Seco because the ecological life of the watershed varies with the seasons. Changes in weather conditions have a great influence on water quality. Heavy rainstorms in the winter and early spring introduce large amounts of pollutants due to runoff. In the summer, reduced flows and higher temperatures caused by dry weather alter the conditions. Baseline monitoring data (chemical, physical, biological) are necessary to identify vulnerable areas to be targeted for improvement.

Water quality in the Arroyo Seco Watershed is degraded in several significant ways. The Hahamongna Basin is a Superfund site due to the presence of volatile organic chemicals and perchlorate. Nitrates from past agricultural practices and septic tank systems are a significant factor in some parts of the watershed. Street runoff from throughout the watershed pollutes the Arroyo Seco stream with trash and contaminants, and the Los Angeles Regional Water Quality Control Board has detected unacceptable levels of coliform from animal waste.

News Coverage

Pasadena Star-News

Long Beach Press Telegram

Here's How the Stream Team Got Started

Stream Team

Wet Feet