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New Study Identifies Mountain Snowpack Most “At-Risk” from Climate Change

As the planet warms, scientists expect that mountain snowpack should melt progressively earlier in the year. However, observations in the U.S. show that as temperatures have risen, snowpack melt is relatively unaffected in some regions while others can experience snowpack melt a month earlier in the year.

This Year Will Likely Be Critically Dry for California, State Officials Say

The winter storms that dumped heavy snow and rain across California early in 2021 are likely not enough to negate what will be a critically dry year, state water officials believe.

California’s Department of Water Resources on Tuesday recorded a snow depth of 56 inches and water content of 21 inches at Phillips Station in the Sierra Nevada. The water content of the overall snowpack was 61% of the average for March 2 and 54% of the average for April 1, when it is historically at its maximum.

California Experiences Fifth Straight Month of Below Average Snow, Precipitation

The Department of Water Resources today conducted the third manual snow survey of the season at Phillips Station. The manual survey recorded 56 inches of snow depth and a snow water equivalent (SWE) of 21 inches, which is 86% of average for this location. The SWE measures the amount of water contained in the snowpack and is a key component of DWR’s water supply forecast.

“As California closes out the fifth consecutive dry month of our water year, absent a series of strong storms in March or April we are going to end with a critically dry year on the heels of last year’s dry conditions,” said DWR Director Karla Nemeth. “With back-to-back dry years, water efficiency and drought preparedness are more important than ever for communities, agriculture and the environment.”

In Rapidly Warming Colorado River Basin, The Negotiating Table Is Being Set

Anyone who has hosted a good dinner party knows that the guest list, table setting and topic of conversation play a big role in determining whether the night is a hit or the guests leave angry and unsatisfied.

That concept is about to get a true test on the Colorado River, where chairs are being pulled up to a negotiating table to start a new round of talks that could define how the river system adapts to a changing climate for the next generation.

Humans Have Completely Transformed How Water Is Stored on Earth

Human fingerprints are all over the world’s freshwater. A new study published Wednesday in the journal Nature shows that while human-controlled freshwater sources make up a minimal portion of the world’s ponds, lakes, and rivers, they are responsible more than half of all changes to the Earth’s water system.

Without Active Spring Snow, State’s Snowpack on Track to be Below Average

Colorado’s high country is just weeks away from its average peak snowpack date. Current measurements are on the fast track to coming up short. “Our snowpack has been struggling. We’re close to average, but not quite to average so the likelihood of getting average snowpack is pretty low at this point. It’s most likely that most areas of our state will have a little bit below average snowpack when we end the season,” said Becky Bolinger, Assistant State Climatologist with the Colorado Climate Center at CSU.

SSJID Worried Drought May be on the Way

The South San Joaquin Irrigation District season is starting March 10 although board members added an asterisk to that decision. Restrictions on water allocation as the irrigation season unfolds loom as a possibility especially if March ends up being mostly dry. The board last week was guided by the conservative outlook the National Oceanic and Atmospheric Administration posted for its California and Nevada River Forecast that includes the Stanislaus River watershed that the SSJID relies on to make deliveries to farmers irrigating 52,000 acres around Manteca, Ripon, and Escalon as well as deliver drinking water to Manteca, Lathrop, and Tracy.

Opinion: As Another Dry Year Looms in California, Key Steps Will Make a Resilient Water Future

On issues ranging from climate policy to immigration and health care, the past four years have been full of discord between California and Washington, D.C. Unfortunately, water users throughout California have not escaped the conflict, including in the Central Valley, where our communities have suffered as a result. Now, with drought conditions returning and the impacts of climate change intensifying, it is time to advance a solution for statewide water policy that will transition us from an era of conflict to one of collaboration.

Phillips Station-Mountain Snowpack-Climate Change-DWR Snow Survey

New Study Identifies Mountain Snowpack Most “At-Risk” from Climate Change

As the planet warms, scientists expect that mountain snowpack should melt progressively earlier in the year. However, observations in the U.S. show that as temperatures have risen, snowpack melt is relatively unaffected in some regions while others can experience snowpack melt a month earlier in the year.

This discrepancy in the timing of snowpack disappearance—the date in the spring when all the winter snow has melted—is the focus of new research by scientists at Scripps Institution of Oceanography at the University of California San Diego.

In a new study published March 1 in the journal Nature Climate ChangeScripps Oceanography climate scientists Amato Evan and Ian Eisenman identify regional variations in snowpack melt as temperatures increase, and they present a theory that explains which mountain snowpacks worldwide are most “at-risk” from climate change. The study was funded by NOAA’s Climate Program Office.

Mountain snowpack changing rapidly in coastal regions

Looking at nearly four decades of observations in the Western U.S., the researchers found that as temperatures rise, the timing of snowpack disappearance is changing most rapidly in coastal regions and the south, with smaller changes in the northern interior of the country. This means that snowpack in the Sierra Nevadas, the Cascades, and the mountains of southern Arizona is much more vulnerable to rising temperatures than snowpack found in places like the Rockies or the mountains of Utah.

The scientists used these historical observations to create a new model for understanding why the timing of snowpack disappearance differs widely across mountain regions. They theorize that changes in the amount of time that snow can accumulate and the amount of time the surface is covered with snow during the year are the critical reasons why some regions are more vulnerable to snowpack melt than others.

Mountain Snowpack-Climate Change-Scripps Institution of Oceanography

Using a new model, the Scripps researchers theorize that snowpack in coastal regions, the Arctic, and the Western U.S. may be among the most at-risk for premature melt from rising temperatures. Graphic: Courtesy Scripps Institution of Oceanography

Snowpack vulnerable due to increasing temperature

“Global warming isn’t affecting everywhere the same. As you get closer to the ocean or further south in the U.S., the snowpack is more vulnerable, or more at-risk, due to increasing temperature, whereas in the interior of the continent, the snowpack seems much more impervious, or resilient to rising temperatures,” said Evan, lead author of the study. “Our theory tells us why that’s happening, and it’s basically showing that spring is coming a lot earlier in the year if you’re in Oregon, California, Washington, and down south, but not if you’re in Colorado or Utah.”

Applying this theory globally, the researchers found that increasing temperatures would affect the timing of snowpack melt most prominently in the Arctic, the Alps of Europe, and the southern region of South America, with much smaller changes in the northern interiors of Europe and Asia, including the central region of Russia.

Climate Change and snowmelt

To devise the model that led to these findings, Evan and Eisenman analyzed daily snowpack measurements from nearly 400 sites across the Western U.S managed by the Natural Resources Conservation Service Snowpack Telemetry (SNOTEL) network. They looked at SNOTEL data each year from 1982 to 2018 and focused on changes in the date of snowpack disappearance in the spring. They also examined data from the North American Regional Reanalysis (NARR) showing the daily mean surface air temperature and precipitation over the same years for each of these stations.

Using an approach based on physics and mathematics, the model simulates the timing of snowpack accumulation and snowpack melting as a function of temperature. The scientists could then use the model to solve for the key factor that was causing the differences in snowpack warming: time. Specifically, they looked at the amount of time snow can accumulate and the amount of time the surface is covered with snow.

“I was excited by the simplicity of the explanation that we ultimately arrived at,” said Eisenman. “Our theoretical model provides a mechanism to explain why the observed snowmelt dates change so much more at some locations than at others, and it also predicts how snowmelt dates will change in the future under further warming.”

A “shrinking winter” and longer fire season

The model shows that regions with very large swings in temperature between the winter and summer are less susceptible to warming than those where the change in temperature from winter to summer is smaller. The model also shows that regions where the annual mean temperature is closest to 0˚C are less susceptible to early melt. The most susceptible regions are ones where the differences between wintertime and summertime temperatures are small, and where the average temperature is either far above, or even far below 0˚C.

For example, in an interior mountain region of the U.S. like the Colorado Rockies, where the temperature dips below 0°C for about half the year, an increase of 1°C can lead to a quicker melt by a couple of days—not a huge difference.

However, in a coastal region like the Pacific Northwest, the influence of the ocean and thermal regulation helps keep the winter temperatures a bit warmer, meaning there are fewer days below 0°C in which snow can accumulate. The researchers hypothesize that in the region’s Cascade Mountains, a 1°C increase in temperature could result in the snow melting about a month earlier in the season—a dramatic difference.

Arctic “at risk”

One of the most “at-risk” regions is the Arctic, where snow accumulates for nine months each year and takes about three months to melt. The model suggests that 1°C warming there would result in a faster melt by about a week—a significant period of time for one of the fastest warming places on Earth.

This study builds upon previous work done by Scripps scientists since the mid-1990s to map out changes in snowmelt timing and snowpacks across the Western U.S. The authors said that a “shrinking” winter—one that is shorter, warmer, and with less overall precipitation—has adverse societal effects because it contributes to a longer fire season. This could have devastating impacts on already fire-prone regions. In California, faster snowpack melt rates have already made forest management more difficult and provided prime conditions for invasive species like the bark beetle to thrive.

Funding for this work was provided by a NOAA/CPO grant to the University of California.

State Water Project Takes Aim at Restoring Salton Sea, Alleviating Health Risks

California is spending more than $200 million to keep an unfolding ecological crisis from getting worse. The state wants to stabilize habitat along the southern bank of the Salton Sea, the state’s largest lake.

That is good news for nearby residents concerned about their health, but the restoration could also affect everyone who draws water from the Colorado River.