Runoff Water Quality

Protecting the quality of runoff is a particularly vexing challenge for Southern California’s water-quality management community. During both wet and dry weather, contaminants wash off the land from across hundreds of square miles of urban and agricultural landscapes. The diffuse nature of runoff has complicated management source-control efforts and impeded progress toward improving water quality.

For decades, SCCWRP has been working to help Southern California water-quality managers methodically study runoff contamination, including documenting where contaminants are coming from and how they’re affecting downstream aquatic ecosystems. More recently, SCCWRP has shifted its focus to developing and evaluating management strategies and tools for improving runoff water quality – in particular, through implementation of runoff control measures known as stormwater BMPs (best management practices).

A SCCWRP researcher collects a stormwater runoff sample at the beach. SCCWRP has worked for decades to document the origins of contamination in runoff and how this contamination affects downstream ecosystems.

Searching for solutions to a pervasive challenge

In Southern California, runoff water quality is degraded by a wide array of pollutants – vehicle fluids, heavy metals, fecal matter, trash, nutrients, toxins, pesticides and fertilizers. As this contamination flows through creeks, rivers and storm drainage infrastructure to the coastal ocean, it can disrupt and destroy sensitive plant and animal communities, as well as sicken humans who swim and surf in contaminated waters.

Multiple regulatory programs have been established to provide incrementally tougher, more prescriptive requirements for protecting runoff water quality. Although Southern California water-quality managers have made progress identifying and curbing major pollution sources, much of the pollution in runoff comes from non-point sources that are vexing to control and eliminate.

Surfers in San Diego paddle away from the shore one day after rainfall. Fecal pollution is one of multiple types of runoff contaminants that SCCWRP has extensively studied – both to document health risks to beachgoers, as well as to investigate solutions for remediating these risks.

Science to support runoff management

As water-quality managers work toward compliance with Total Maximum Daily Load (TMDL) regulations and other programs for improving runoff water quality, SCCWRP is turning to science to answer pressing questions about the scope of runoff contamination challenges and how managers can optimally address them. To help Southern California managers focus on areas where runoff challenges are most significant, SCCWRP has built foundational tools for estimating what levels and types of contaminants can be expected to run off the land based on how the land is being used. More recently, SCCWRP has been developing strategies and tools to help managers optimize the effectiveness of stormwater BMPs for reducing contamination in runoff.

Storm drain systems such as this one that terminates at Newport Bay in Orange County carry land-based contaminants to coastal waters. SCCWRP has played a key role in helping environmental managers understand what levels and types of contamination are in this runoff, as well as how to design and implement potential solutions for reducing runoff contamination.