California's reservoirs swell in the wake of winter storms

Water levels fell so low in key reservoirs during the depth of California's drought that boat docks sat on dry, cracked land and cars drove into the centreof what should have been Folsom Lake.

Those scenes are no more after a series of powerful storms dumped record amounts of rain and snow across California, replenishing reservoirs and bringing an end mostly to the state's three-year drought.

Now, 12 of California's 17 major reservoirs are filled above their historical averages for the start of spring. That includes Folsom Lake, which controls water flows along the American River, as well as Lake Oroville, the state's second-largest reservoir and home to the nation's tallest dam.

It's a stunning turnaround of water availability in the nation's most populous state. Late last year, nearly all of California was in drought, including at extreme and exceptional levels. Wells ran dry, farmers fallowed fields and cities restricted watering grass.

The water picture changed dramatically starting in December, when the first of a dozen "atmospheric rivers" hit, causing widespread flooding and damaging homes and infrastructure, and dumped closeto 18 metresof snow in the Sierra Nevada mountains.

"California went from the three driest years on record to the three wettest weeks on record when we were catapulted into our rainy season in January," said Karla Nemeth, director of California Department of Water Resources. "So, hydrologically, California is no longer in a drought, except for very small portions of the state."

All the rain and snow, however, may bring new challenges. Some reservoirs are so full that water is being released to make room for storm runoff and snowmelt that could cause flooding this spring and summer, a new problem for weary water managers and emergency responders.

Flooding expected

The storms have created one of the biggest snowpacks on record in the Sierra Nevada mountains. The snowpack's water content is 239 per centof its normal average and nearly triple in the southern Sierra, according to state data.

As the weather warms up, water managers are preparing for all that snow to melt, unleashing a torrent of water that's expected to cause flooding in the Sierra foothills and Central Valley.

"We know there will be flooding as a result of the snowmelt," Nemeth said. "There's just too much snowmelt to be accommodated in our rivers and channels and keeping things between levees."

Managers are now releasing water from the Oroville Dam spillway, which was rebuilt after it broke apart during heavy rains in February 2017, and forced the evacuation of more than 180,000 people downstream along the Feather River.

The reservoir is 16 per centabove its historic average. That's compared to 2021, when water levels dropped so low that its hydroelectric dams stopped generating power.

That year, the Bidwell Canyon and Lime Saddle marinas had to pull most recreational boats out of Lake Oroville and shut down their boat rental business because water levels were too low and it was too hard to get to the marinas, said Jared Rael, who manages the marinas.

In late March, the water at Lake Oroville rose to 262 metresabove sea level, about 70 metreshigher than its low point in 2021, according to state data.

"The public is going to benefit with the water being higher. Everything is easier to get to. They can just jump on the lake and have fun," Rael said. "Right now we have tons of water. We have a high lake with a bunch of snowpack. We're going to have a great year."

The abundant precipitation has prompted Gov. Gavin Newsom to lift some of the state's water restrictions and stop asking people to voluntarily reduce their water use by 15 per cent.

Some shortages remain

Newsom has not declared the drought over, however, because there are still water shortages along the California-Oregon border and parts of southern California that rely on the struggling Colorado River.

Cities and irrigation districts that provide water to farms will receive a big boost in water supplies from the State Water Project and Central Valley Project, networks of reservoirs and canals that supply water across California. Some farmers are using the stormwater to replenish underground aquifers that had become depleted after years of pumping and drought left wells dry.

State officials are warning residents not to let the current abundance lead to wasting water. In the era of climate change, one extremely wet year could be followed by several dry years, returning the state to drought.

"Given weather whiplash, we know the return of dry conditions and the intensity of the dry conditions that are likely to return means we have to be using water more efficiently," Nemeth said. "We have to be adopting conservation as a way of life."