In a recent Water Watch issue, titled “New Storage Finally on the Horizon,” we mentioned a new study by the University of California, Davis regarding water storage. The study, authored by Tiffany Kocis and Helen Dahlke, quantifies “high-magnitude flows” – i.e. surface water flows above the 90th percentile when compared to all other years, like the flows seen during this year’s historically wet winter. The authors estimate that an additional 2.6 million acre-feet of water is available from an average high-magnitude event.
That’s a lot of water – enough to irrigate 867,000 acres of farmland, provide water for 5.8 million families or 23 million Californians, or the average annual groundwater overdraft in the Central Valley.
These findings come at a crucial time. With the 2014 passage of the Sustainable Groundwater Management Act (SGMA), local Groundwater Sustainability Agencies around the state are hard at work preparing Groundwater Sustainability Plans, carefully balancing every available drop of water to recharge these depleted aquifers. As the state continues to recover from five years of historic drought, these aquifers could use all the extra water they can get.
The UC Davis researchers suggest that if the extra water from these high-magnitude events could be redistributed to the San Joaquin and Tulare Basins, there could be considerable groundwater recharge and aquifer recovery. However, in order to do so California’s broken water system needs some serious upgrades.
The study submits, and we agree, that projects like Sites Reservoir and the California WaterFix could provide the operational flexibility needed to capitalize on these high-magnitude opportunities. More above ground storage would allow water managers to capture and store these peak flows for slower releases as groundwater aquifers soak up the extra water. The study cites the 2017 Department of Water Resources report, Water Available for Replenishment, that points to water infrastructure capacity as “a limiting factor to full use of high-magnitude flows for groundwater banking.” Improved conveyance capacity through projects such as the California WaterFix would help with this impediment.
The alternative is letting 2.6 million acre-feet of excess water wash out to sea while groundwater aquifers could be moving more quickly towards sustainability.
This opportunity comes against the backdrop of a pending State Water Resources Control Board Bay-Delta Plan update that would call for an unprecedented increase in unimpaired flows (water required to be left in the river for environmental purposes), likely resulting in a severe decrease in available surface water for families, farmers and groundwater recharge.
Policy makers need to act swiftly to improve infrastructure and operational flexibility to ensure the next high-magnitude opportunities are captured, not lost. Equally important, the State Water Resources Control Board needs to recognize their policies to increase unimpaired flows and the Department of Water Resources’ goal of achieving groundwater sustainability are not aligned. State agencies must get on the same page, otherwise families, business and the environment will continue to suffer!