Toward the Human Right to Water for Vulnerable Communities: The Effectiveness of Stakeholder Processes to Control Regional Shallow Groundwater Contamination by Nitrates

Nitrate contamination in shallow drinking water wells is an urgent and persistent concern for agricultural regions and disadvantaged communities worldwide. As viable options for the large‐scale removal of nitrates from groundwater remain elusive, greater emphasis has been placed on stakeholder‐based integrative approaches, yet few have been developed, and fewer evaluated for their effectiveness. The Central Valley in California is one of the most important intensive agricultural regions globally, where such a stakeholder‐based process (CV‐SALTS) has been initiated, and which is poised to serve as a model for controlling nitrate contamination elsewhere. Based on the Groundwater Ambient Monitoring and Assessment Program data for the 2000–2023 period, we develop a new data sufficiency metric, quantify the uncertainties associated with establishing nitrate concentrations and their changes in space and time, the impact of Confined Animal Feeding Operations (CAFOs), seasonal variability and drought on nitrate levels, and how they are addressed through CV‐SALTS policies. Our findings suggest that there remain substantial uncertainties associated with where nitrate concentrations are above safe levels, but that they predominantly intersect with environmental justice communities. Severe drought conditions and the proximity of CAFOS significantly elevated nitrate concentrations, but had previously not been sufficiently monitored or considered. A new data sufficiency metric based on nitrate variability, maximum contaminant level exceedance, and observation density can support stakeholder processes in prioritizing areas for additional monitoring and risk reduction. Our findings form the basis for recommended policy changes that are transferable to other regions.