Arroyo Grande Lagoon, located near the mouth of Arroyo Grande Creek on California’s Central Coast, is a seasonal estuary that forms when sandbars block creek flow into the Pacific Ocean. The lagoon is part of a 154-square-mile watershed that receives an average annual rainfall of 15 to 20 inches, concentrated during winter storms. These sandbar closures create a dynamic lagoon environment where water levels, salinity, and oxygen conditions fluctuate based on seasonal changes and storm events.

The lagoon provides critical habitat for steelhead trout and other aquatic species, serving as a nursery and migratory pathway. However, human influences, such as urban runoff, upstream agricultural activity, and channel modifications, can degrade water quality, alter sediment transport, and exacerbate flooding risks during high flow events. The sandbar dynamics also pose challenges for managing water levels, which can impact nearby farmland and infrastructure.

Real-time water level monitoring at Arroyo Grande Lagoon tracks sandbar formation, flooding patterns, and seasonal hydrology, providing essential data to inform habitat restoration, flood mitigation, and water quality management. This integrated approach helps address the complex interactions between natural processes and human impacts in this sensitive estuarine system.