Characterizing shallow groundwater nutrient sources in central coast sloughs

Start/End: February, 2018 to February, 2020

Of the 124 Marine Protected Areas (MPAs) along the California coast, eighteen are coastal estuaries. These MPAs help protect a unique set of coastal ecosystems, supporting numerous environmental services and addressing challenges faced at the land-sea interface.

Ten of the protected estuaries are impaired by nutrient loading and/or low dissolved oxygen concentrations, often associated with upstream agricultural discharges. Despite efforts by the agriculture industry to become compliant with water quality regulations, downstream water quality remains polluted with nutrients. Recent studies suggest that groundwater containing old fertilizer runoff could be confounding agricultural efforts to improve water quality management. 

By measuring multiple tracers (radon-222, nitrogen isotopes, and water quality parameters), this project will establish a sampling framework to evaluate the relative contribution of shallow groundwater, irrigation, and surface water nutrient loads to estuarine waters. 

By understanding irrigation and groundwater interactions, industry and state agencies will better document success of adopted actions and further define steps industry and agencies can take to meet water quality objectives.