Snowpacks in the Western US are trending smaller because of climate change, and the dwindling runoff that supplies meltwater to the Colorado River is a sign that western water supplies are threatened.
Snowpack, Snow Drought and the Western US
Snowpacks in the United States are a critical water reserve, but climate change induced hot spots are sparking “snow droughts” that threaten water resources. The US Drought Portal describes snow drought as “a period of abnormally low snowpack for the time of year, reflecting either below-normal cold-season precipitation (dry snow drought) or a lack of snow accumulation despite near-normal precipitation (warm snow drought).” Snow droughts are caused by warm temperatures, precipitation falling as rain instead of snow or abnormally early snowmelt – in short, when the snow doesn’t fall and accumulate when and where people want it to.
A recent study by UC-Irvine examined how detrimental snow droughts are to mountain snowpack meltwater. With new methods developed, they compared water availability from snowpack in distant places and found that the negative impacts are widespread.
Researchers evaluated such snowpack-dependent mountain ranges as the Hindu Kush and the greater Himalayas in Asia; the Andes mountain range and Patagonia in South America; the Alps in Europe; and the Rocky and Sierra Mountains in the North America.
Afghanistan, reliant on the Hundi Kush mountains, was noted for its extreme vulnerability because about three-quarters of the country’s snow-covered area faced widespread drought from December 2017 to March 2018. Snowmelt is critical for crop irrigation, yet the country does not have dams or other infrastructure to store runoff. The snow drought has not only caused food shortages and monetary loss for millions of Afghans, but leaves them at risk to both droughts and floods.
The impacts to agriculture are significant, especially in the hub of US agriculture, California. As UC-Irvine co-author, Dr. Laurie Huning stated:
Snowmelt provides freshwater to more than a billion people, one sixth of the world’s population. Water from melting snow irrigates the crops of farming regions including areas that seldom if ever receive any snow during the winter, such as California’s Central Valley— so it’s important from an agricultural resources standpoint to have a clear picture of snow drought trends and their impacts.
California, which relies heavily on western snowpacks for water supplies, was hit hard during the 2014-15 drought. The agricultural sector experienced losses estimated at $2.7 billion in revenues and 18,600 jobs. The drought originated from the combined effects of low snowpack, low precipitation and hot temperatures. Reservoir water levels dropped throughout the larger system, which led to reduced hydropower production and greater consumption of fossil fuel-based electricity that increased greenhouse gas emissions, further amplifying the climate crisis.
The Colorado River is a significant part of California’s water supply, and, in total, supports more than 40 million people in the American southwest who use it for drinking water, agriculture, power generation and healthy ecosystems. For those who experience the downstream flow of mountain snowpack as essential for life, there is real concern that the climate crisis might be shifting the baseline to an even drier environment, which, in turn, will lower Colorado River water levels. If droughts of any type – hot droughts, dry droughts and snow droughts – are permanent, then the Colorado River Basin might well be moving into a new climate regime of aridification.
Colorado River Water Levels in a Climate Hot Spot
Elevated heat in high mountain elevations represents yet another way climate change spells water supply worries. This was reiterated when the biggest US climate change hot spot was identified as a large section of the Colorado River Basin, which continues to suffer a 20-year drought as snowpack dwindles and runoff dries up. The hot spot covers Colorado’s Western Slope and three neighboring counties in eastern Utah, an area that has warmed more than 2 degrees Celsius, double the global average, according to a Washington Post analysis. The extreme heat wave currently scorching the western US is a concerning reminder of this warming trend.
As climate change markedly heats up in this dryland region, the average flow of the Colorado River has declined 19 percent from 2000 to 2014, with approximately one-third (if not more) due to warming temperatures.
Over time, these higher temperatures have shrunk snowpack levels in the Rocky Mountains, the natural water storage for the region that melts off and feeds the river. Increased warming induces smaller snowpack, earlier melt, more evaporation, more rain and less snow, all of which produce less runoff for the river. Just last week, Arizona and Nevada announced that they would be forced to accept water allotment cuts triggered by low reservoir levels in Lake Mead, a process that’s part of the 2019 Lower Basin Drought Contingency Plan agreed upon by the states that share Colorado River water.
Broadly speaking, the Colorado River exhibits “hot drought” conditions of high temperatures that causes higher evaporation rates, as opposed a “dry drought” that refers to lower average precipitation over time.
Reduced flow in the Colorado River has serious repercussions even at the most personal level.
Longtime Colorado farmer, Norman Kehmeier, has firsthand experience with “hot drought” on his fourth-generation ranch.
“In all my years of farming in the area, going back to about 1950, 2018 was the toughest, driest year I can remember,” the 94 year-old Colorado farmer told the Washington Post.
The conundrum for Kehmeier and his family is whether it makes more economic sense to sell their valuable water rights or continue to operate their fourth-generation ranch.
Under such conditions, adapting to a new way of life under a more water-scarce reality is no longer an afterthought but a critical new normal. Now, gazing at white-tipped mountains often becomes something more profound, and wet.
Written by Kai Olson-Sawyer.