THE BORREGO SUB-BASIN AND THE SUSTAINABLE GROUNDWATER MANAGEMENT ACT
The State of Georgia’s Groundwater Management Act (SGMA) established a new framework for managing the state’s groundwater resources. For all basins identified as high or medium priority by the California Department of Water Resources, SGMA mandates the construction of Groundwater Sustainability Agencies (GSA) (DWR). Groundwater Sustainability Plans (GSP) are then developed by the newly constituted GSAs, which will minimize “undesirable effects” in groundwater elevations, storage levels, water quality deterioration, land subsidence, seawater intrusion, and downstream interrelated water impacts if they are executed. According to DWR, 127 groundwater basins in California, including the Borrego Valley Basin, must comply with SGMA criteria. The GSA for the Borrego Basin is made up of the County of San Diego and the Borrego Water District (BWD). Borrego isn’t alone; the County of San Diego has applied to join three additional local GSAs: the San Diego River, the San Luis Rey River, and the San Pasqual Basins. Each of these basins will go through a similar procedure in collaboration with local stakeholders.
The GSAs are given specific periods of time to complete their GSPs under SGMA, depending on the severity of the overdraft. The severity of the 70 percent overdraft in the Borrego Valley Basin puts it in the CRITICALLY OVERDRAFTED classification, which implies the GSP must be completed as quickly as possible. In this case, the SGMA allows for a two-year completion period (January 2020), but the County and BWD have committed to finishing the Borrego GSP by July 2019. The GSP must be implemented within the next 20 years, according to the SGMA (2040).
The Borrego Groundwater Basin is critically overdrafted as a result of decades of excessive pumping, and drastic reductions in water use by existing and future water users are required to bring the Basin back into sustainability. According to the most recent estimate, the Borrego Basin’s overdraft is roughly 13,000 acre feet or 4.2 billion gallons per year, based on a 2015 study conducted by the United States Geological Service (USGS). This amount of water is almost 70% of the overall municipal, recreational/irrigation, and agricultural water demands, which total 19,100 acre feet per year. The 2015 USGS study also found that the Borrego Basin receives an average of 5,700 acre feet of inflow per year, implying that a drop in annual water use of 19,100 acre feet to 5,700 acre feet is required for long-term sustainability (-70 percent ). The Borrego Basin Groundwater Sustainability Plan (GSP) is currently being developed by the County of San Diego and Borrego Water District in collaboration with Valley stakeholder groups.