Water quality monitoring is crucial to maintaining the health of habitat and water resources. This program identifies contaminant levels in the Arroyo Seco and sets the stage for corrective measures.
Arroyo Seco Foundation volunteers collect water samples from the stream and test the levels of a set of parameters, such as pH, dissolved oxygen, and bacteria. Anyone can participate! If you are interested, please let us know at info@arroyoseco.org.
The water quality data collected will:
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, and 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.
For more information, see Developing a Citizen Water Quality Monitoring Program in the Arroyo Seco, a complete guidebook for water quality testing and improvement in the Arroyo Seco.
Samples are collected from 11 locations along the main stem of the Arroyo Seco. These sites were established by the Los Angeles County Department of Public Works as being important for determining the condition of the stream in general. You can view a map of them here.
The presence of certain substances in water indicate conditions that are harmful to individual organisms and a balanced ecosystem. The parameters ASF tests include:
For more information on these parameters and why they are important, see our water quality parameters page.
Arroyo Seco Water Quality Monitoring Handbook
March 2013
ASF Report | PWP Report