Aptos Creek Lagoon, located on California’s Central Coast in Santa Cruz County, is a small, seasonal estuary where Aptos Creek meets the Pacific Ocean. The lagoon spans less than half a mile and is part of a 25-square-mile watershed. Seasonal sandbar formation at the mouth often blocks tidal exchange, creating a dynamic brackish environment shaped by changes in freshwater inflow, salinity, and oxygen levels.

This estuary provides important habitat for steelhead trout and other aquatic species, offering a protected nursery area for juveniles and a passageway for migrating adults. However, human activities such as urban runoff, infrastructure, and development in the watershed can affect water quality and sediment transport, disrupting natural processes. Sandbar closures during the wet season can also lead to elevated water levels, posing flooding risks to nearby infrastructure and property.

Water level monitoring at Aptos Creek Lagoon helps track these seasonal shifts and supports informed management decisions. The data contribute to habitat conservation, guide flood mitigation planning, and help balance ecological function with human needs in this sensitive coastal system.