The Pescadero Lagoon Estuary, located on the central California coast in San Mateo County, is a dynamic and ecologically rich coastal system where Pescadero Creek flows into the Pacific Ocean. This intermittently-closed estuary features a mix of freshwater and brackish habitats, including tidal marshes, mudflats, and a coastal lagoon. These diverse environments support a wide range of species, including steelhead trout, tidewater goby, and numerous migratory birds that rely on the estuary during key parts of their life cycles.

A sandbar regularly forms at the estuary’s mouth, temporarily blocking tidal exchange with the ocean. The timing and duration of these closures affect salinity, water levels, and nutrient dynamics, shaping the availability and quality of habitat throughout the year. These shifts create complex ecological interactions and make the estuary especially sensitive to changes in freshwater flow, rainfall, and ocean conditions.

The Pescadero Lagoon Estuary faces challenges from land use changes, upstream water diversions, sedimentation, and pollution. As a result, it has become a critical site for restoration, habitat protection, and scientific study. Monitoring water levels and breaching events provides essential data for understanding how the system functions and for guiding efforts to improve its long-term ecological health and resilience.