As snow in the mountains of the western United States decreases, new research from Berkeley Lab analyzes when a low-to-no-snow future is likely to arrive and its impact on water management. Snow cover in mountains around the world is decreasing. If the earth continues to warm, climate models predict that snow cover may shrink sharply, and may even disappear completely in certain mountains sometime in the next century, including in the western United States.
A new study led by researchers at Lawrence Berkeley National Laboratory (Berkeley Lab) analyzes the possible time from low snow to no snow in the future, what it means for water management, and investment opportunities that can now avoid disastrous consequences.
They published a review article “A low-to-snow-free future and its impact on water resources in the western United States” published in the journal Nature Review-Earth and Environment. They analyzed previous climate predictions and found that if greenhouse gas emissions continue to be high Emissions programs, low to snow-free winters will become a regular phenomenon in the western United States within 35 to 60 years. In addition, the study reassessed the long-standing assumptions in water management in the United States, and emphasized that scientists and water managers need to work more closely to develop and implement climate adaptation strategies.
The Sierra Nevada, Rocky Mountains, Karst Mountains and other mountain ranges provide tremendous services by capturing, storing and releasing water for downstream use. Historically, the snowmelt time has provided a critical delay for water supply in spring and summer, when precipitation is low and agricultural water demand is greatest. The factors leading to the shrinkage of snowdrifts are mainly related to temperature rise and changes in precipitation characteristics. Warm temperatures also mean that storms will produce more rain and less snow, limiting the amount of seasonal snow that can form in winter.
This research was led by Erica Siirila-Woodburn and Alan Rhoades, authors in the field of earth and environmental sciences at Berkeley Lab. Starting from a literature review, hundreds of scientific studies on snow loss were extracted; in these studies, they determined and Analyzed 18 studies that quantitatively predict snow in the western United States.
When will the future from low snow to no snow come?
“A recent study highlighted that since the 1950s, the amount of snow storage in the western United States on April 1 has fallen by 21%-which is equivalent to the storage of Lake Mead. In our review, we found We should expect a similar decline in snow cover around the middle of this century,” Rhoades said. “By the end of this century, the decline may reach more than 50%, but the scope of uncertainty is greater.”
Many water resources managers use the somewhat arbitrary date of April 1 for snow cover observations and planning decisions. In the past few decades, the peak of snow cover has declined, and the time of peak snow cover has also been advanced. For every temperature increase of 1 degree Celsius (1.8 degree Fahrenheit), the peak value will be advanced about 8 days in the year. Appear.
Many areas have experienced winters with very little snow in recent years. For example, in the Sierra Mountains in 2015, the snow cover on April 1st was 5% of the normal level, which the author called an “extreme” event. The document defines two other types of low to no snow conditions-“incidental low to no snow”, or when more than half of a mountain basin has experienced low to no snow for five consecutive years, and “continuous low to no snow”. “Snow” has occurred in this case for 10 consecutive years. “Low snow” is defined as when the snow pack (or more accurately, snow water equivalent, which measures how much water will be released when the snow pack melts) is at the 30th percentile or lower of the historical peak.
Using these definitions, based on a high-resolution climate prediction, California will experience occasional low to no snow as early as the late 2040s, and continuous low to no snow in the 2060s. For the rest of the western United States, sustained low to no snow will appear in the 1970s. The author reminds that more analysis is needed with broader climate forecasts to strengthen confidence in the timeline of low to no snow conditions.
The authors describe the climate predictions in their research, writing “In the middle and late 21st century, compared to historical periods, more and more areas of the western United States were affected by insufficient snow water equivalent. Especially, in 1950-2000 During the period, only 8-14% of the years are classified as low to snow-free, while in the period 2050-2099, the proportion is 78-94%. In all regions, a sudden change occurred approximately in the mid to late 21st century “.
Impact on water resources
The impact of a low-to-snow-free future is not just a reduction in streams, although this is certainly an important consequence. For example, in the Sierra Nevada, the typical snow cover on April 1 is almost twice the amount of water stored in surface reservoirs in California.
Siirila-Woodburn said: “A low-to-snow-free future will have a huge impact on the location and timing of water storage in the western United States.” In addition to its direct impact on tourism and other aspects, from a hydrological point of view, it has an impact on nature and management. The system also has many secondary effects. As a result, many results will change accordingly, such as from an increase in the incidence of wildfires to changes in groundwater and surface water patterns, and changes in vegetation type and density. “
As snow decreases and rain increases, the groundwater level of mountain systems may be affected because snowmelt seeps into the ground more efficiently than rainfall. In addition, the reduction of snow in low-altitude areas will reduce the total surface area of snow stored in mountainous areas, which may result in a decrease in the amount of snowmelting agents that can penetrate into the ground.
The purpose of the author’s research is to stimulate current thinking on adaptation strategies. Rhoades said: “We hope that society will take the initiative, not passiveness, to these snow changes. When we introduce a literature review of low to no snow, we hope to understand this issue in a’one-stop’ way. In addition, we emphasize Some novel climate adaptation strategies have been produced through the cooperation of non-traditional academic and water agencies, which will be a key part of the combination of adaptation methods needed to overcome snow loss in a warmer world.”
One such partnership is a project called HyperFACETS supported by the Department of Energy, which involves 11 research institutions, including Berkeley Labs, and works with managers of water utilities in California, Colorado, Florida, and Pennsylvania.
The document also discusses potential adaptation strategies, such as a technique known as managed aquifer recharge, in which excess surface water is stored as groundwater for later use. Another relatively new technology, predictive reservoir operation, in which weather and hydrological forecasts are used to inform decisions about retaining or releasing reservoirs, recently showed a 33% increase in water storage in Lake Mendocino, California.
These and other technologies show the promise of increasing water supply, but the authors also recommend more cross-cooperation among scientists and across society to expand the portfolio of climate adaptation strategies.
“We advocate the idea of participating in best scientific practices, as well as more cooperation or partnerships between researchers and stakeholders. For example, city managers are concerned with flood control; farmers are concerned with water storage; everyone has their own The goal. Even within science, the disciplines are usually isolated,” Siirila-Woodburn said. “If everyone worked together to manage water instead of working independently for their own purposes, there would be more water available.”