Central Sierra snowpack is a third of average, but researchers say there’s time for a turnaround

Thirty seven percent of the historical average. 

That’s the current snowpack measurement at Donner Summit. Which stings a little more when coming off a near record-setting season.

But when you have the perspective of more than 75 years, you know better than to write off the rest of winter, while understanding how the season has become much more challenging over time.

“Even though we're starting off in kind of a slow, and maybe a little bit of a precarious, spot with our snowpack, that doesn't necessarily mean it'll stay that way,” said Andrew Schwartz, the lead scientist at the UC Berkeley Central Sierra Snow Lab, which measures precipitation, snowfall, snow depth, and air temperature.  

Perched at an elevation of 6,894 feet, the lab has been at Donner Summit since 1946, with records that date back to the 1800s. 

“We have one of the longest records in the world,” he said.

Schwartz joined CapRadio Insight Host Vicki Gonzalez with a look at how December is shaping up as well as introducing some new instruments to measure snowpack. 

This interview has been edited for clarity and length. 

Interview Highlights

Tell us about the UC Berkeley Central Sierra Snow Lab and what scientists like you do. 

We have been up here on Donner Summit since about 1946. And we've been researching all things water, weather, climate since then. We take daily measurements of our snowpack and put those into our database, and we also look at how the weather's affecting that. And actually, even though we've only been here since 1946, we have one of the longest records in the world that goes all the way back to 1878. So really cool stuff up here.

Last season was a near record-breaking snow season. We’re in mid-December. How does this season compare so far? 

Realistically, last year was the second biggest we've had on record. The only bigger year was 1951-52. We ended up getting about 63 feet last year of snowfall. And the record-breaking year was 68 [feet], so pretty close to that. This year, we're a little bit behind the ball. 

Since we’re currently below the historical average, should we expect that to stay consistent for the rest of this winter?

No, not at all. We've had these slow starts to the year before. Probably the most recent one that ended up panning out really well for us was in the winter of 2016-2017. We got a really late start to that year. We were getting almost no snowfall. And then about midway through January, the snow took off and just did not stop for a couple months. That's one of the biggest years in recent memory for a lot of people. So even though we're starting off in kind of a slow, and maybe a little bit of a precarious, spot with our snowpack, that doesn't necessarily mean it'll stay that way.

Your measurements are focused on the central Sierra. How is this season so far in the southern and northern Sierra?

We've seen more snow go up north. Last year the thing that brought us so much of that wonderful moisture was those atmospheric rivers that kind of hit the Central Coast and went down south a little bit, too. But this year those storm tracks have been much further north up in Washington, Oregon and in British Columbia. And so that means they're getting all that moisture and we've kind of been on the southern edge. The snow that we have gotten has been primarily in the northern Sierra Nevada and in the southern Cascades. We've had a little bit here in the central Sierra, but the southern Sierra is also hurting because they haven't had too much yet. 

We have been experiencing more precipitation than snowfall in recent years. How challenging is that in terms of water storage to carry us through the drier months?

It can be immensely challenging. A lot of people, myself included, for a very long time kind of considered rain and snowfall to be the same in terms of our water needs. You realize that snow is immensely important, and that rain doesn't quite fulfill the same role. We have these big reservoirs around the state that store our water. But our snowpack exists as another reservoir on top of the mountains that we don't have to manage. It manages itself. It can give us a consistent feed of water through the spring and into the summer — last year even into the fall. So it's a really valuable asset. And as we all probably notice it was a lot less smoky this last summer as well, which means that when we do have that good snowpack, it really helps keep our vegetation moist and lower our fire danger. So when we get a slow start to the year like this, it's not the end of the world, but we're definitely hoping that it bulks up soon.

Are snow seasons getting shorter?

They are, yes. So we're seeing, of course, warming of the atmosphere as a whole. But that warming has taken kind of what we call the ‘fringe months of winter.’ So October, November, April and May, when things used to be below zero Celsius or below 32 degrees Fahrenheit at night, that would support a snowpack, and it’s brought those temperatures above that. So now in those months we've seen a big shift away from snowfall as the dominant precipitation type, to rainfall. And that makes it challenging because, for one, if we're recreating the ski resorts can't open as early as we would like. And that makes it hard for them to operate, and they have to invest in snowmaking equipment. But it also presents issues because we don't get that early start to the snowpack that really helps wet our soil and set us up for a successful water year.

You have some new instruments this year. Tell us about them. 

We embarked on a new project with our partners of the Department of Water Resources to install about 25 to 30 new sensors here at the site. I've kind of dubbed it the ‘sky to stream’ measurement system, because from the moment that a snowflake or a raindrop falls out of the sky, until the moment it goes downhill in a stream, it's being measured — whether that be with wind speed and air temperature, or in a number of different ways. This is realistically the biggest investment that we've had on this site in decades for our measuring capabilities. 

If we kind of break it down a little bit, there's two ways that we really measure snow and our snowpack. There's what we call mass balance, which is the mass coming in versus the mass going out. So mass coming in is just snow or rain. And then mass going out is going to be melt water going down streams, sometimes evaporation, sometimes soil recharge. And then we have energy balance, which is all the energy sources going into and out of that snowpack that caused it to melt. And this new system will be doing all of those measurements. And we'll also have a live streaming camera. So you can see what the conditions are like up here during those big storms that roll through.

What do these sensors look like?

We have big precipitation gauges. We have something that I worked on heavily for my Ph.D. called an Eddy Covariance Sensor. It kind of looks like one spider on its back, and another one facing on its top with these crazy legs that point at each other. And it measures 3D wind speed and then takes measurements of carbon dioxide and water vapor and air. So we can figure out how much is going into and out of the environment. We've got a sensor in our stream now that's measuring our stream level. So we're really understanding how our stream flows respond to certain events like rain on snow. And it's just a very exciting time. This will be the first winter this system's tested in its complexity and completeness. And then hopefully next year we'll be fully operational and all the data can go out to whoever would like to see it. 

That must be pretty cool for you seeing it go from an academic setting into the environment. 

It's incredibly exciting. It's one of those things where there's very few sites, if any around the world, that have this complete of a measurement system for our atmosphere and for snow. Off the top of my head I can think of maybe three or four [sites] that would be up there with us. So it really is a groundbreaking system and it's been so great to see it come to fruition.