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OC Watersheds implements monitoring and assessment programs designed to inform program management decisions and 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 (OC Stormwater Program). 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 picture_as_pdf Santa Ana Region of Orange County See the following links for maps of Santa Ana Region monitoring sites:

Monitoring Program Goals

While these programs satisfy MS4 permit requirements, the overall goal of the monitoring, assessment, and research efforts is 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 as detailed in the explore Santa Ana State of the Environment Report prepared in 2013

SAR Monitoring chart

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?

The following three monitoring & assessment themes, also detailed in the State of the Environment Report, provide a foundation and framework for evolving the program to provide more effective information to support smarter stormwater management.

  • Theme 1: Focus on priority areas and constituents rather than trying to monitor all constituents, potential problems, and locations
  • Theme 2: Increase the integration of data from a wider range of sources in order to leverage the value and impact of the Program’s efforts to address the five assessment questions
  • Theme 3: Continue evolving from a strictly discharge-specific approach to a risk prioritization approach that can highlight problem areas and support more flexible monitoring designs that include data driven adaptive triggers

Additional Programs

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 ( monitoring/southern-california-bight-regional-monitoring-program/ ) – 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. 

Water Quality Monitoring Data

Santa Ana Region of Orange County (north and central watersheds) 

Data from water quality and other environmental monitoring efforts in the north and central watersheds of  Orange County (Santa Ana Region) is summarized and analyzed on an annual basis in Section 11 of the Orange County Stormwater Program Unified Program Effectiveness Assessment (Unified PEA).  The Unified PEA is finalized by November 15th of each year and covers a reporting period of July 1st through June 30th.  

(Please note that all water quality monitoring data is reported in Section 11 of the document). 

Data Requests 

All data requests should be submitted through MyOCeServices  - please select the "Information Only" service request category.