New analysis of snowpack data by two research groups has changed conventional understanding of the mechanics of snowmelt: Both teams found warmer weather may change the amount of snow as well as how it melts.
These studies are important in developing a better understanding of the amount of water available in snow (known as snow-water equivalent). This information can be used to calculate the amount of runoff bound for reservoirs and available for hydrogeneration. Understanding this influence on water shortages and surpluses is particularly meaningful information for water managers in times of drought.
Both studies also found the snowmelt analysis can be applied to ecosystem health and flood risks.
Earlier Snowpack Melt
Warmer conditions worldwide will cause mountain snowpack to melt earlier in the year and also melt more slowly, scientists from the National Center for Atmospheric Research found.
Keith Musselman, a post-doctoral researcher on the project, explained:
When snowmelt shifts earlier in the year, the snow is no longer melting under the high sun angles of late spring and early summer. […] The Sun just isn’t providing enough energy at that time of year to drive high snowmelt rates.
This supports other research, which found that as temperatures increase, average streamflows may decline in watersheds reliant on mountain snowpack. This should hold true even if the total amount of precipitation in the watershed remains unchanged, because the snowmelt has more time to be absorbed into the ground.
Consequences of Warming Weather
To confirm anecdotal observations, the researchers looked at a decade of snowpack data from the United States and Canada. They ran models to determine what could happen if the climate continues to warm.
The consequences, while not a part of the study, could include less spring flooding, which could have adverse consequences, such as warming, for river habitats.
Less streamflow also could cause water scarcity in urban areas if less water from snowmelt makes it to reservoirs.
According to a new Oregon State University study, recent anomalies in that state’s snowpack may not be anomalies at all. Oregon had very low snowpack levels in 2014 and historically low levels in 2015. The study found this is related to warmer temperatures, not less precipitation. Researchers say this could become the norm if average temperatures increase by 2 degrees Celsius.
Eric Sproles, the study’s lead author, explains:
California received a lot of attention for its drought, but the economic and environmental impacts from those two low-snowpack years were profound in the Pacific Northwest. We set out to learn whether they were just off years, or if they would be likely to happen more often with increased warming. Unfortunately, the data show these will become more commonplace.
In 2015, when 47 percent of the snow monitoring sites in the Willamette River basin registered zero snow-water equivalent in March, there were reduced summer stream flows, water quality challenges in the Willamette River watershed, increased wildfires, high fish mortality rates, and “a dreadful season for ski resorts.” Some of the ecological issues were precipitated by low water levels and high concentrations of blue-green algae.
The study shows how incredibly sensitive the region’s snowpack is to increasing temperatures. […] The low snow years took place even though precipitation wasn’t that bad. But when it falls as rain instead of snow, it loses that ability to function as a natural reservoir in the mountains.
He added the full consequences are not yet known. Typically, water takes seven or more years in the watershed to percolate through the ground before it feeds into the Willamette River.
Both studies demonstrate how much more there is to discover about the intricacies of hydrology and how the mechanics of the water cycle affect water management.