California's Snowpack Melting Early as Record Heat Hits

Rapid snowmelt threatens to strain state's reservoir system

Mar. 21, 2026 at 7:56pm

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A record-breaking heat wave in California is causing the Sierra Nevada snowpack, which provides about a third of the state's water supply, to melt much earlier than usual. This rapid snowmelt is complicating efforts by reservoir operators to store enough water for the drier summer months, as federal flood control rules limit their ability to capture the runoff. While California's reservoirs are currently in good shape, the early loss of the crucial snowpack reservoir is raising concerns about water supplies in the months ahead.

Why it matters

The Sierra Nevada snowpack is a vital source of spring and summer runoff that refills California's reservoirs when the state needs the water most. Climate change is causing this snowpack to melt earlier each year, putting strain on the state's water management system and raising questions about long-term water security.

The details

Historically, the Sierra Nevada snowpack reaches its deepest levels in April, but this year it has already dropped to 38% of average for mid-March. The snowpack is disappearing at a rate of around 1% per day, a sharp departure from the near-average conditions of last year. Reservoir operators are struggling to capture this early runoff due to federal flood control rules that require them to maintain empty space in the reservoirs until June. This is complicating efforts to store enough water for the drier summer months ahead.

  • In early to mid-March, the Sierra Nevada snowpack has been disappearing at a rate of roughly 1% per day.
  • Historically, the Sierra Nevada snowpack is at its deepest in April.

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.

Don Seymour

Deputy director of engineering at Sonoma Water, which co-manages Lake Mendocino.

Willie Whittlesey

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

Andrea Pook

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

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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, Central Valley Project

“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, Yuba Water Agency

“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, East Bay Municipal Utility District

What’s next

Reservoir operators are working with the U.S. Army Corps of Engineers to update decades-old flood control rules that limit their ability to capture early snowmelt. They are also exploring new forecasting and water management techniques, like the Forecast Informed Reservoir Operations program used at Lake Mendocino, to better adapt to the impacts of climate change.

The takeaway

The rapid melting of California's crucial Sierra Nevada snowpack due to record heat is straining the state's reservoir system, highlighting the need for more flexible and adaptive water management strategies to cope with the effects of climate change. Improving forecasting, updating outdated regulations, and adopting innovative approaches like forecast-based operations can help California's water agencies better prepare for and respond to the shifting water supply patterns driven by a warming climate.