Man sampling water quality with bucket

Watershed Monitoring Program

Program Objectives:

The Watershed Monitoring Program is a major cornerstone of implementing stormwater compliance. Water quality monitoring includes: 

  • Assess chemical, physical and biological impacts of municipal stormwater and dry weather flows on receiving waters
  • Characterize quality of stormwater and dry weather discharges to identify pollutants and evaluate trends of pollutant contribution within each respective watershed
  • Conduct regular monitoring at facilities (i.e. MS4 outfalls and receiving waters) to determine flow, ambient water quality parameters, and field conditions
  • Identify long-term changes to receiving water quality conditions
  • Analyze data to determine the impact of urban runoff and measure potential impacts to receiving water quality and its beneficial uses
  • Track water quality outcomes of watershed, document pollutant loadings and/or trends in pollutant loadings for specific watersheds or outfall

What’s an MS4?

MS4 is short for Municipal Separate Storm Sewer System. MS4s are conveyances or systems of conveyances including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains that are owned or operated by a public entity, are designed or used for collecting or conveying stormwater, and are not a combined sewer or part of a publicly owned treatment works

Consolidated Monitoring Program

There are three areas in Riverside County under Permittee jurisdiction. They are known as the Santa Margarita River Watershed (SMR), the Middle Santa Ana River Watershed (SAR), and the Whitewater River Region (WWR), each named after their respective watershed. Each watershed is governed by a separate Regional Water Quality Control Board (Water Board) and separate NPDES permits for which the District is listed as Principal (or Co-Principal) Permittee. The Riverside County Flood Control and Water Conservation District (District), as the Principal Permittee, administers the CMP on behalf of the Permittees named in the three NPDES permits in Riverside County.

The Consolidated Monitoring Program (CMP) was created to incorporate and describe the monitoring methods for each type of monitoring conducted by the District on behalf of the Permittees.

Model Monitoring Program for Municipal Separate Storm Sewer Systems in Southern California (MMP).

The goal of the MS4 Urban Runoff Monitoring Program is to manage the quality of urban runoff to prevent impacts to receiving waters within the Permittees’ respective jurisdictions. 

The District anticipates significant growth will occur within its Monitoring Program; thus, the CMP will continue to be updated, and progress will be reported in subsequent Monitoring Annual Reports

For more information you may contact Rebekah Guill at (951) 955-1200

Regional Monitoring Efforts

The Southern California Stormwater Monitoring Coalition (SMC) was formed in 2001 by Phase I municipal stormwater NPDES lead permittees, the NPDES regulatory agencies in southern California and the Southern California Coastal Water Research Project. Each of the NPDES MS4 permits with Riverside County require some level of participation in the SMC’s regional monitoring efforts. Refer to the watershed-specific monitoring plans, corresponding annual reports, or the SMC webpage to learn more.

Monitoring Documents



Post-Fire Monitoring

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