California Prepares for Extreme Weather Swings as New Water Year Approaches

Record hot summer, looming La Niña conditions, and early-season uncertainty means California must be prepared for both dry conditions and flood risk.

SACRAMENTO, Calif.- The Department of Water Resources (DWR) today previewed the new Water Year which starts on October 1 by highlighting preparations for more extreme weather events this season following a record hot summer across much of California and a looming La Niña pattern.

Over the past decade, climate extremes have posed significant challenges to water managers, especially the extreme hot and dry conditions that frequently persist well past summer months and into the fall. California is seeing that right now with above-average temperatures forecast into October and no rain in the current forecast. At the same time, the water that California does receive will arrive from more powerful storms, and hotter temperatures will mean less winter precipitation falls as snow and more will arrive as rain, increasing flood risk.

"California has experienced the full range of climate challenges in recent years from extreme drought to severe flooding and we will be seeing more of that in the future," said DWR Director Karla Nemeth. "To meet these dramatic challenges, California is starting this water year with more accurate forecasting and additional investments in flood protection and groundwater recharge."

DWR and partner agencies are making California more climate resilient, taking actions to protect and boost California's water supplies by taking an all-of-the-above approachto creating a resilient water supply in the face of a changing climate.

Investments in Forecast Informed Reservoir Operationsand improved data collection on hydrological conditions across the state through DWR's $7 million California Stream Gage Improvement Program(CalSIP) will allow California to incorporate the best available science and data into its water management decisions.

California is also investing in protecting Californians from extreme weather events. Floodplain restoration and flood infrastructure projects such as the Lookout Slough Tidal Habitat Restoration and Flood Improvement Projectand the Lower Elkhorn Basin Levee Setback Projectwill work with nature to improve wildlife habitat while reducing flood risk to hundreds of thousands of Californians.

California is also starting this water year with significant progress in bringing groundwater basinsacross the state closer to long-term sustainability, protecting drinking water supplies against the impacts of climate change. Last winter, DWR launched the Flood Diversion and Recharge Enhancement Initiative, which supports local groundwater recharge efforts that increase the volume of flood flows diverted from local waterways to recharge areas and expand local capacity to divert and receive future flood flows. DWR has invested over $100 million in groundwater recharge projects since the Sustainable Groundwater Management Act was signed into law in 2014.

While Lake Oroville, the State Water Project's largest reservoir, is currently 101 percent of average for this date, the latest outlookfrom NOAA's Climate Predication Center shows a 71 percent chance of La Niña conditions emerging this fall. While seven of the 10 La Niña events this century resulted in dry years, research also suggests that even as the climate grows hotter and drier overall, the precipitation that California does receive will arrive in stronger storms, increasing the risk from flooding.

"California experienced record heat and dry conditions this summer, drying out the landscape and putting our hydrology behind before the water year even starts," said State Climatologist Dr. Michael Anderson. "While there is still a lot of uncertainty around how La Niña could impact the state this year, we know we can count on it to include extreme conditions."

The record dry conditions this summer broke multiple records across the state for consecutive days of triple digit temperatures. In the critically important Sierra Nevada watersheds, precipitation this fall will be vitally important to ensure the winter snowpack can translate into runoff that fills our reservoirs, which provides a third of the water used in California.

In addition to today's preview of the new Water Year, DWR will also release the 2024 Annual Water Supply and Demand Assessment Summary Reporton Monday, September 30. The summary report, which includes water shortage information at the supplier level, as well as regional and statewide analyses of water supply conditions, finds that all suppliers have assessed that they will have adequate supplies to meet demand in the coming year.

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Additional Resources (will be available at the links below shortly)

• Recordingof Today's Media Briefing
• PowerPointPresentation from Today's Briefing