News•April 26, 2017

California Got More Snow This Winter Than Past 4 Total

That it was wet this winter in California is an understatement. After four years of drought, the Golden State faced a whiteout of epic proportions.

Mountains were caked in nearly 800 inches of snow and ski resorts are slated to stay open into summer to take advantage of snowpack unseen in years. Reservoirs filled, dams overtopped with nearly calamitous consequences and a once-in-a-decade wildflower bloom sprung up in Death Valley.

New data reveals just how extreme this winter was while also putting the four bone-dry years preceding it in perspective. According to the NASA Earth Observatory, this year’s end-of-winter snow water equivalent — a measure of snowpack health taken each April 1 — was greater than the total snow water equivalent measurements taken from 2013-16 in the Tuolumne River Basin.

Credit: NASA Earth Observatory

That basin includes the Hetch Hetchy Reservoir, San Francisco’s main water source. Snowpack remains up to 215 percent above normal for this time of year and it contains enough water in the basin to fill the Rose Bowl 1,600 times.

Overall snowpack in the central Sierra Nevada is up to 199 percent above normal for this time of year with other parts of the mountain range reporting similarly prolific numbers.

It’s a major flip from famine to feast following four consecutive years of drought conditions that left mountains brown and reservoirs dangerously low. That includes 2015, when snowpack hit its nadir. That April, there wasn’t any snow to measure at many locations, an extreme unprecedented in at least 500 years.

The watery feast-and-famine cycle is one that’s becoming more common according to a 2016 study, which found that near-normal precipitation years are becoming more rare.

“What seems to be happening is that we're having fewer 'average' years, and instead we're seeing more extremes on both sides,” Daniel Swain, a PhD candidate at Stanford and author of the study, said in a statement last year.” This means that California is indeed experiencing more warm and dry periods, punctuated by wet conditions.”

The past few winters are indicative of that trend. Swain and other scientists are working to tease out whether the cause of this tip toward more extreme wet and dry years is a sign of climate change or a natural pattern for the state.

One area where climate change did a play a role in the drought is turning up the heat and drying out soils. Temperatures are projected to climb to 10°F higher by century’s end in the Sierra Nevada if carbon pollution continues at its current rate. Days with extreme heat could increase by an order of magnitude from a handful a year to up to 50 days annually.

Research suggests that by 2030 the warm conditions that locked in the drought could become an annual occurrence. That doesn’t mean every year will be a drought year, in part because big precipitation changes aren’t likely in California. It does mean that when dry years do hit, they’ll likely be reinforced by hot weather, so enjoy the wet, relatively cool years while you can.