Will California’s extreme storms offset its years-long drought?

Located on the West Coast of the United States, California — the country’s most populous state — has experienced a devastating, multiyear drought that has depleted reservoirs, forced officials to plead with residents to conserve water and constrained supplies to vital farmland.

But over the last three weeks, the state has been hit by a sudden, severe series of storms, with more expected in the coming days.

The rain is soaking a state that desperately needs water, even as it takes a devastating human toll. The office of Governor Gavin Newsom estimates that at least 17 people have been killed during the extreme weather.

While experts say the precipitation will help drought conditions, it isn’t yet clear exactly how much. And the rain and snow won’t be enough to fix some of California’s long-term water problems that climate change is making worse.

“We are transitioning to a climate that is warming and more arid,” said Jeannie Jones, the interstate resources manager at the California Department of Water Resources.

Here’s how the storms will likely affect California’s long struggle with drought.

Where is the rain helping?

California has experienced heavy precipitation from six atmospheric rivers — narrow bands of concentrated water vapour — in recent weeks.

And the state is bracing for as many as three more, with the wild weather set to continue for at least another week, Governor Newsom said on Tuesday, January 10 from Santa Cruz County, where raging ocean water damaged an iconic wooden pier.

The storms have poured a tremendous amount of water on the state, especially in central California, including the San Francisco Bay Area and Sacramento Valley. Precipitation is 138 percent of average for this time of year, officials said. The storms have also dumped snow on the Sierra Nevada mountain range that runs along California’s eastern border.

Most of the state’s reservoirs remain below average for this time of year, but some have begun to fill, especially those close to the hard-hit Sacramento region and along parts of the Sierra Nevada.

The reservoirs are essential for irrigating the Central Valley, a productive stretch of farmland that grows large amounts of fruits, nuts and grains. The reservoirs also supply water to millions of people living in coastal cities.

For example, a small reservoir in Sonoma County that was at roughly half its historical average on December 25 had risen to 80 percent of that average by January 9.

“What we’ve got so far puts us in good shape, probably for at least the next year,” said Alan Haynes, the hydrologist in charge of the California Nevada River Forecast Center.

Snowpack is its own type of reservoir, storing moisture that ideally melts slowly into reservoirs, supplying residents with water during the drier months of summer and fall. But now that snowpack often melts too quickly and reservoirs aren’t able to capture enough of it.

“The California system was built for a climate we don’t have anymore,” said Laura Feinstein, who leads work on climate resilience and environment at San Francisco Bay Area Planning and Urban Research Association (SPUR), a public policy non-profit.

Where could the storms fall short?

It’s still early in the winter and it’s unclear what the next few months will bring. Last year, statewide snowpack around this time also looked promising. But a few warm, dry months followed, and when snowpack was supposed to peak in early April, it was just 38 percent of the historic average.

“We are not out of the drought yet,” said Feinstein.

Plus, the storms haven’t dropped as much water on Northern California. The state’s largest reservoir at Lake Shasta, which was at 55 percent of its historical average on December 25, had risen to 70 percent by January 10 — an improvement, but still well below historical averages due to years of water scarcity, according to Haynes.

The atmospheric rivers aren’t striking everywhere. They move around “like a garden hose if you are spraying it across the yard”, said David Gochis, an expert in how water affects the weather at the National Center for Atmospheric Research in Boulder, Colorado.

“Those biggest reservoirs are just so massive it is probably going to take a while for them to fill,” he said. For some of the biggest, most crucial reservoirs, it may take five or six such drenchings, he said.

David Novak, director of the National Weather Service’s Weather Prediction Center, says the atmospheric rivers still to come will likely be weaker. The problem is the already wet ground will not be able to absorb much more water, creating problems with runoff. In about 10 days, weather patterns may shift and finally “turn off the spigot”, he said.

And the Colorado River, a major source of water for Southern California, has also been stricken by drought that has depleted major reservoirs on that river. The recent storms won’t fix that problem.

What about long-term issues like climate change?

Many farmers in California pump water from underground, with the enormous amounts pulled from aquifers depleting groundwater. Some wells are running dry. It is an entrenched problem and is not going to be solved by a short-term series of storms, experts said.

“Our management of land has prevented it from being recharged very well,” said Mike Antos, a watershed specialist at Stantec, a consulting company. He says the Central Valley needs more places for water flows to seep down and replenish aquifers.

And California is facing a long-term problem. Although there have been some wet years mixed in, California’s drought has been going on for roughly two decades. Climate change is creating drier, hotter conditions. Water evaporates faster. California officials predict there will be less water in the state’s future.

“So in that big picture, this series of storms really is kind of just a drop in the bucket,” Jones said.