Water Quality Monitoring

The Environmental Monitoring Division of OC Watersheds implements monitoring programs to comply with municipal separate storm sewer system (MS4) permit requirements on behalf of the County, the Orange County Flood Control District, and the 34 cities of Orange County. Since Orange County is within the jurisdiction of two Regional Water Boards (Santa Ana and San Diego), there is a monitoring plan for each region of Orange County, as follows:

MS4 Permit Monitoring Plan for the Santa Ana Region of Orange County
See the following links for maps of Santa Ana Region monitoring sites:    

MS4 Permit Monitoring Plan for the San Diego Region of Orange County (maps of monitoring sites included in document)

While these programs satisfy MS4 permit requirements, the overall goal of the monitoring, assessment, and research efforts are intended to track progress toward solving existing problems, identify emerging issues that could become problems in the future, and support research and development that improves our understanding of key processes and advances the efficiency and effectiveness of monitoring methods. The approach is based on answering the following five assessment questions:

  1. Is there a problem?
  2. If so, what is its magnitude and extent?
  3. What are the sources of the problem?
  4. Are conditions getting better or worse?
  5. Are management actions working as intended?



OC Watersheds is also a participating agency in the following efforts to examine emerging water quality issues and environmental concerns for Southern California at the regional scale:

  • Southern California Bight Studies – The Bight studies, coordinated by the Southern California Coastal Water Research Project (SCCWRP), utilize standardized sampling and analytical methods to produce a wide range of data from both impacted and reference areas.
  • Stormwater Monitoring Coalition (SMC) – The SMC often use exploratory data analysis methods to investigate new measurement methods, improve basic understanding, characterize problems, or provide one-time measurements of important parameters or processes.