California Snowpack Melting Early, Straining Reservoir Levels

Record-breaking heat and early snowmelt are challenging water managers to adapt reservoir operations for the new climate reality.

Mar. 21, 2026 at 7:06pm

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A warm wet storm following February's snow, and record-breaking March temperatures are shattering records in California, prompting warnings of rapid snowmelt and swift rivers. The Sierra Nevada snowpack, which provides about a third of the state's water supply, is disappearing much earlier than usual, leaving less water trickling down the mountains in warmer months for homes, farms, fish, hydropower and forests. Reservoir operators are working to adapt their management strategies, but rigid federal rules and aging infrastructure are complicating their efforts to capture and store the early runoff.

Why it matters

California's snowpack is a vital source of spring and summer runoff that refills the state's reservoirs when water is needed most. But climate change is shifting this runoff earlier, leaving less water available during the dry summer months when demand is highest. This early melt poses challenges for reservoir managers who must balance flood control and water storage, and could lead to water shortages if the trend continues.

The details

The Sierra Nevada snowpack is currently at 38% of average for mid-March, rapidly approaching the worst five on record for April 1. Reservoir operators like the Yuba Water Agency and the East Bay Municipal Utility District are struggling to capture and store the early runoff due to rigid federal flood control rules and aging infrastructure. They are working with state and federal agencies to update outdated operating rules and improve forecasting to better adapt to the new climate reality.

  • In mid-March, the snowpack has been disappearing at a rate of roughly 1% per day.
  • Historically, the snowpack is at its deepest in April, but climate change is shifting the runoff earlier.

The players

Levi Johnson

Operations manager for the Central Valley Project, the massive federal water system that funnels Northern California river water to the Central Valley and parts of the Bay Area.

Michael Anderson

California state climatologist.

Willie Whittlesey

General manager of the Yuba Water Agency, which operates the New Bullards Bar reservoir.

Andrea Pook

Spokesperson for the East Bay Municipal Utility District, California's second-largest urban water supplier.

Andrew Schwartz

Director of UC Berkeley's Central Sierra Snow Laboratory.

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What they’re saying

“In an ideal world, you'd have your reservoir full right now, and this additional huge snowpack reservoir that we know will help replenish and provide more water supply. We're not going to have that.”

— Levi Johnson, operations manager

“We're seeing snowmelt conditions in mid-March that we normally don't see until at least mid-May. It's pretty obvious that this is the runoff — this is the snowmelt — and it's just happening about two months early.”

— Willie Whittlesey, general manager

“We're tracking to not necessarily be in a drought situation. But I am not convinced that we're going to fill our reservoirs by July 1, which is our usual goal.”

— Andrea Pook, spokesperson

What’s next

The Yuba Water Agency is working with the U.S. Army Corps of Engineers to update decades-old flood control rules that are complicating their ability to store the early snowmelt. The California Department of Water Resources is also seeking permission from the Army Corps to store more water in Lake Oroville beyond normal flood control limits.

The takeaway

California's water managers are facing a new climate reality, with snowpack melting much earlier due to record-breaking heat. This is straining the state's reservoir system, which was designed around historical snowmelt patterns. Adapting reservoir operations and updating outdated rules will be crucial to ensuring reliable water supplies in the face of a rapidly changing climate.