Decision support tools for participatory sustainable groundwater management in California

One hundred years of government agency inaction on groundwater sustainability management in California was reversed in 2014 with passage of the Groundwater Sustainability Act, (SGMA) https://water.ca.gov/Programs/Groundwater-Management/SGMA-Groundwater-Management. Unregulated groundwater pumping has, since the last major California drought of 2012-2013, led to a significant increase in the number of deep aquifer wells installed and a return of land subsidence in some of the most intensively farmed agricultural area – some areas dropping more than 0.5 metres annually in recent years. The State of California has adopted an innovative stakeholder-centric approach to SGMA planning and implementation through a requirement that stakeholders form locally controlled groundwater sustainability agencies (GSAs) with the authority to fund local governance to collectively support and protect groundwater resources. These GSAs are responsible for preparing groundwater sustainability plans (GSPs) and implementing SGMA through cooperation and coordination with other Basin GSAs to address: (a) persistent lowering of groundwater levels; (b) significant reductions in groundwater storage; (c) saltwater intrusion; (d) degradation of water quality and (e) irreversible land subsidence. Although the State of California promoted use of well documented, public domain, regional integrated surface and groundwater models for GSA decision support and long-term planning through the 2040 compliance deadline - stakeholders have largely ignored these tools and instead adopted simpler conceptual modeling approaches. This instance of basin-scale, water resource planning process oversight is not uncommon in agency-led participatory modeling and decision support whereby shared conceptual understanding of a problem and potential solutions among stakeholders trumps model performance and accuracy of results. This is especially true given the long-term resource implications of any negotiated groundwater management plan. This paper describes the rationale and successes to date of the SGMA planning process and the challenges ahead when using models for GSA planning purposes as the State of California grabbles with one of the most serious resource management problems in its 200-year history.