Adopted in 2014, the Sustainable Groundwater Management Act (SGMA) sets milestones that must be met to achieve groundwater sustainability. The law requires formation of local groundwater sustainability agencies—or GSAs—to guide groundwater management in basins and sub-basins classified by the state as medium or high priority.
Groundwater matters to everyone. It’s an important source of water stored in the earth beneath our feet, in spaces between sand, soils, and fractured rock known as an aquifer. Layers of aquifers make up a groundwater basin, which can extend for miles. Groundwater is a critical buffer against the impacts of drought and climate variability/change and plays a vital role in maintaining our region’s (and the State’s) economic and environmental sustainability. Sustainable groundwater management balances groundwater resources in a manner that ensures basin resiliency, which greatly benefits present and future generations.
The San Benito County Water District is the GSA for the North San Benito Basin and prepared a Groundwater Sustainability Plan (GSP) in partnership with Santa Clara Valley Water District (now known as Valley Water), for small areas of the basin that extend into Santa Clara County. The North San Benito Basin is the result of consolidation of the previously defined Bolsa, Hollister, San Juan Bautista, and Tres Pinos Valley basins. This consolidation of basins, approved by DWR in 2019, supports comprehensive and cost-effective management.
The local GSP was completed in November 2021 and is still in review at the state level. The GSP provides the basic information, analytical tools, and projects and management actions for continued groundwater management, guided by SGMA and by locally defined sustainability goals, objectives, and metrics.
The levels of our groundwater is not a straight forward answer. The levels differ throughout the basin. I can’t tell you we have “x” amount of water in the entire basin right now. Some areas showed larger declines than others. In general, in 2021 groundwater elevations declined slightly throughout most of the basin. This is the second year of groundwater declines after a three-year period of groundwater recovery after the last major drought. With continued drought conditions; groundwater levels will decline further, especially with zero CVP allocations. That’s why Sunnyslope, Hollister and San Juan will all be implementing Stage II of our Water Shortage Contingency Plan the first week in May. This will be mandatory water conservation measures aimed mainly at outdoor water use.
The basin when full holds approximately 500,000 acre-feet of water. It was almost full at the beginning of this current drought. We use approximately 40,000 acre-feet of water per year ( 30K agriculture and 10K residential).
During wet years the District tries to fill the basin so we can use it during dry years. Local water from Hernandez Reservoir is run down the San Benito River to fill the aquifer. The Sunnyslope County WD, San Juan and Hollister all have wells that take advantage of this. Also, when the District gets large allocations of water during wet years they will percolate water into the basin. The City of Hollister’s Reclamation Plant after recycling wastewater and treating it to high standards, also helps percolate water and delivers recycled water to agricultural and landscape accounts. It’s all about the balance!
The first groundwater report since the adoption of the GSP was produced in March 2022. One of the changes to the annual groundwater reports associated with SGMA compliance is the inclusion of groundwater contours for the entire basin. A consequence of this basin-wide approach is inclusion of areas with limited or no previous groundwater monitoring. The Annual Groundwater Report documents water sources and uses, groundwater elevations and storage, and management activities for the Water Year and provides recommendations.
One of the recommendations is to improve the monitoring programs to provide the SBCWD Board of Directors with information to support management of the groundwater supplies. Detailed monitoring recommendations were developed as part of the GSP, including accurate measurement of groundwater pumping, which has been identified as an important data gap.
Past District percolation operations helped to reverse historical overdraft and then accumulate a water supply reserve. The District currently manages groundwater storage and surface water to minimize excessively high or low groundwater elevations. Another recommendation is the District should continue to operate Hernandez and Paicines to improve downstream groundwater conditions. The District provided off-channel percolation of Central Valley Project water (imported to county); this too should be continued given availability of CVP water and persistence of local low groundwater levels. Basin-wide analysis of opportunities for additional percolation is being conducted as part of the Managed Aquifer Recharge Study.
To read the Groundwater Report for Water Year 2021, go to: https://sbcwd.temp312.kinsta.cloud/wp-content/uploads/2022/03/SGMA-Annual-WY21-FINAL-032222.pdf
To learn more about the GSP, go to: https://www.sbcwd.com/resources-and-documents/