Snow Droughts
Atmosphere Daily Earth Science Hydrosphere Repost

Snow Droughts

The word ‘drought’ conjures up images of deserts and parched fields of corn. But keep in mind that drought is an extended period of lower than normal precipitation. Snow droughts occur in the cold of winter, high in the mountains. Winter snow and ice feed the water towers of the world. When the snow doesn’t fall, the consequences can be dire. 

‘Water tower’ is a term referring to freshwater locked away in the form of mountain ice and snow. These mountain reservoirs hold more ice than anywhere else on earth, other than the polar regions. During the warm months, the meltwater from these water towers feeds a steady supply of fresh water to many of the world’s mighty rivers. Meltwater from glaciers of the Karakoram, Hindu Kush and Himalayan ranges feeds the Indus river, providing life to over 120 million people.

In the United States, water towers supply rivers like the Colorado, Columbia, and Missouri. Mountain snow and ice are critical components of ecosystems in the headwaters of these rivers. But snow droughts deprive them of needed water resources. The knock-on effect of low water supplies carries on downstream, affecting farms and cities.

American West

The American West has suffered from drought for the past two decades, and scientists now believe the area is in a megadrought cycle. The word ‘drought’ denotes a prolonged period with less water than average. The term megadrought changes the understanding of “prolonged” to encompass decades as opposed to years. Research tells us that the last megadrought in western America ended before the Pilgrims landed in 1620.

The effects of this latest megadrought are far-reaching and challenge the current system of water regulation and distribution across the West. Lake Mead is only 40 percent full, and if it drops another 25 feet, then water restrictions will go into effect across much of the southwestern USA.

 But megadroughts bring less precipitation in all forms, and that includes snow. Every April, researchers measure the snowpack depth throughout the mountains of the American West. The year 2012 was terrible, with greatly reduced snowpacks. The following two years also yielded disappointing results, and in 2015 some sites in the Sierra Nevada mountains were barren of snow.

As the climate warms, the western mountains are receiving less snow, and the length of the snow season is growing shorter. Generally, a single year with a low volume of snow-fall has a minimal impact on the region’s water resources in terms of water shortages. However, two back-to-back years of snow droughts start to impact water usage and planning.

Warmer temperatures and less water

The recent years of snow drought are not one-off events. Hydrologists have revised their models to reflect likely long-term drought conditions in the American West. The chance of two-year snow droughts has increased from 7 percent to 42 percent, and the chances of a four-year drought moved up to 25 percent. 

These predictions impact agriculture, municipal water supplies, and recreation activities. Farmers were hit hard during the last 4-year California drought. Since the state accounts for 13 percent of the USA’s agricultural revenue, more people than just Californians are affected. The shortened snow season also impacts a large winter sports industry. Peak snowpack traditionally occurred in April, but that is now shifting back to March or even February, creating shorter ski seasons.

Megadroughts create lower precipitation conditions year-round. Less rain and less snow translate into less available water and hotter, dryer wildfire seasons. If we are genuinely in a megadrought cycle, then these events will become the norm.


ArcheanWeb:

The world’s water towers (Source: ArcheanWeb) – https://archeanweb.com/2019/12/19/the-worlds-water-towers/  Also:

Hot and dry in the Western USA, a megadrought in progress (Source: ArcheanWeb) – https://archeanweb.com/2020/04/21/hot-and-dry-in-the-western-usa-a-megadrought-in-progress/  Also:

The Colorado River is running dry (Source: ArcheanWeb) – https://archeanweb.com/2020/03/03/the-colorado-river-is-running-dry/  Also:

Sinking ground – Water in the American West (Source: ArcheanWeb) – https://archeanweb.com/2020/05/06/sinking-ground-water-in-the-american-west/  Also:


Sources:

‘Snow droughts’ are coming for the American West (By ALEJANDRA BORUNDA; National Geographic) – https://www.nationalgeographic.com/environment/2019/08/snow-droughts-coming-to-winters-western-us-california-water/  Also:

Feature Image: Fricaba covered by snowpack (Modified) – By Eggbones – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=82900514

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.

Leave a Reply

Your email address will not be published. Required fields are marked *