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Most people recognize a bad drought when they see one. Lakes and rivers recede from normal water levels, crops wither in fields, lawns turn brown, and rivers and streams become less frequent. These droughts are usually attributed to a lack of rain. However, scientists can also track drought in other ways.
“The common ways to measure droughts are through precipitation, soil moisture and runoff,” says Laurie S. Huning, an environmental engineer at the University of California, Irvine. Her latest work examines water stored in snowpack and adds an additional dimension to this equation.
Huning is co-author of a study on the Proceedings of the National Academy of SciencesWith U.C. Irvine colleague Amir AghaKouchak, who developed a new framework for characterizing “snow droughts.” These can occur when there’s an abnormally low snowpack, which may be triggered by low precipitation, warm temperatures or both.
Their research is timely. This winter, southwestern states have received just a quarter to half of the average snow-water equivalent —the amount of water held in the snowpack — the key metric for determining a snow drought.
It can have huge consequences. The water content in a snowpack can have an impact on when runoff occurs and how much. wildlife, ecosystems and water resources, flood control, hydropower, drought mitigation.
Snow droughts can also have far-reaching effects on agriculture — and economies. California’s Central Valley, the heart of its agriculture industry, relies on snow melt from the Sierra Nevada. After low precipitation and warm temperatures in 2014-2015, the sector suffered losses of $2.7Billion.
In regions already struggling with conflict and resource shortages, snow droughts can make things worse. In Afghanistan, a 2017-2018 snow drought resulted in 10 million people being food insecure due to crop failures and livestock loss.
The concept of a “snow drought” has been around for several years, and it’s been studied in certain key locations, but until now scientists and water managers lacked a worldwide method to assess them.
This is the goal of the study. Huning and AghaKouchak developed a standardized snow water equivalent index to help better compare and characterize the duration and intensity snow droughts around the globe.
Some areas are already of concern, according to the results. The researchers looked at data from 1980 to 2018 and found some hotspots in which snow-droughts became more intense and prolonged during the 21st Century.
The western United States saw the most notable increase in snow drought durations, with 28% more. However, the effects on Europe and Eastern Russia were less severe.
On the flip side, snow drought durations decreased in some areas, including the Hindu Kush and Central Asia.
“It’s important to remember that not only does the snowpack vary but the impact that it has differs across the world,” says Huning.
Huning hopes that the framework for the study will help water managers better understand snowmelt’s timing and how it affects water management. He also hopes to integrate drought monitoring systems with the framework to improve resilience and management of resources.
“We know that the snowpack is highly variable,” she says. “Further development of this framework can improve our near real-time monitoring of drought.”
The study didn’t delve into the specifics of Why? snow droughts may be becoming more severe in certain places, but other studies have found that climate change is playing, and will play, a role in reducing snowpack in some areas — including western U.S. states.
A studyUCLA climate scientists published their findings on August 10, showing that California’s warmer temperatures will lead to more rain and less snow in the coming decades. This will increase flood risk and decrease the snowpack, which usually melts slowly in the spring months.
An earlier research showed that a decrease in Arctic sea iceThis causes changes in atmospheric circulation, which creates an atmospheric ridge off the Pacific coast. These ridges act as a deflector of storms, pushing them northwards and leaving the region high-and-dry. A particularly stubborn system that developed in 2013, nicknamed the “ridiculously resilient ridge,” had a big hand in California’s five-year drought, which extended until 2017.
Water managers will have another tool in their arsenal to plan for similar droughts and better manage this resource.
“Snow is a natural resource and, given the warming temperatures that some parts of the world will see, the amount of snow is changing,” says Huning. “We need to recognize that there are so many different ways the environment and humans will be affected.”
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