Climate Whiplash – California Flooding During Drought

Over the past several weeks, a series of storms have lashed California, causing widespread damage across the state, including significant flooding of homes, landslides, sinkholes and road closures, downed trees, and sadly, loss of life.  More than a billion dollars of storm damage is estimated to have occurred already, with more storms heading our way.

At the same time, the storms have also dumped much needed snow and rain, coming on the heels of the driest three year period in California’s modern history.  The state’s snowpack is now more than 200% of average for this date and over 100% of the April 1 average. 

While this year is off to a good start in terms of water supply, sadly it’s too early to declare that the drought is over. 

For instance, just last year we saw how major December storms and above average snowpack melted during record dry conditions from January to March, resulting in continued drought.  So while the deep snowpack is encouraging, it doesn’t guarantee that we’ll have even average snowpack in April.

When it comes to groundwater, the unsustainable pumping during the drought is likely to take decades to recover from. 

And when it comes to water storage, even as the State’s 1,400 dams and reservoirs are capturing a lot of water from these storms, storage at the state’s largest reservoirs storage levels remain below average.  Some reservoirs, like Folsom Dam on the American River and Friant Dam on the San Joaquin River, have been in flood operations in recent days, releasing more water than is coming into these reservoirs in order to protect downstream communities from damaging floods later this year (releasing water now to make room for the water that is expected to flow into the reservoirs in the coming weeks and months).  Yet even as some reservoirs are facing too much water and are going into flood operations, the State’s largest reservoirs (Shasta Dam and Oroville Dam) have millions of acre feet of empty storage, as these reservoirs were drained during the drought.  Moreover, these storms haven’t been evenly distributed across California, with some areas getting too much water and other regions hoping for more – at least after we all have some time to dry out!

In other words, California is both in flood and drought at the same time.

As of midnight on January 10th, on average the 48 reservoirs that the California Department of Water Resources tracks on its Daily Reservoir Storage Summary were less than half full:

Storage Capacity

Actual Storage

Storage Change

Percent of Capacity

Average Storage

Storage-Year Ago This Date

     28,938,460

   14,134,260

      496,374

49%

   16,849,788

        12,382,774

On the plus side, we’re capturing a lot of water from these storms – at just these 48 reservoirs, nearly half a million acre feet of water was captured and stored on January 10th!  Between December 29 and January 10, storage in just these 48 reservoirs increased by almost 3.5 million acre feet.  And in the coming weeks and months, the snowpack and storms will produce runoff that increases storage in many of these reservoirs, although it’s still early to know for sure how much runoff will flow into our rivers and reservoirs later this year (at Shasta Dam, for instance, a recent forecast from the California-Nevada River Forecast Center predicted runoff into the reservoir could range this year from 4.5 million acre feet under dry conditions (90% exceedance) to 5.8 million acre feet under median conditions (50% exceedance) to 8.3 million acre feet under wet conditions (10% exceedance)).

However, California also uses a lot of water – in an average year, agriculture uses around 30 million acre feet of water in the state, with cities using several million acre feet more.  So don’t be surprised if, despite these storms, we continue to face dry conditions later this year with limited water allocations for contractors of the CVP and SWP.  

And we shouldn't forget that water flowing down our rivers and through the Bay-Delta thanks to these storms provides huge ecological benefits for salmon and other native fish and wildlife.  Populations of many native fish and wildlife species in the Bay-Delta have been declining in all but the really wet years, largely because of unsustainable water diversions.  And during the drought, salmon and other native fish have been hammered, so these high flows are much needed respite for these species -- and for the Native American Tribes, thousands of fishing jobs, and all of us who care about their health. 

Drought and floods, all in the same year: the new normal of climate whiplash.

About the Authors

Doug Obegi

Director, California River Restoration, Water Division, Nature Program

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