Supplying Water

Irrigating Crops

If you have ever eaten an almond or a grape, there is a good chance that some of the water that allowed it to grow came from snow. The Central Valley in California, which produces 40% of the fruits and nuts grown in the United States, receives much of its water supply from the San Joaquin River, which is fed by melting snow from high in the Sierra Nevada mountains (USGS, n.d.-a). Like many crop-producing areas, irrigation is essential to produce a harvest. The summer months in particular are dry in this part of California, and water that seeps into underground aquifers is quickly used up. Because mountain snow melts late in the spring or early in the summer, and because it melts gradually, water from snow is available during the summer when rain is uncommon in the Central Valley.

Throughout much of the western U.S. and dry areas in other parts of the world, melting snow at high elevations is an important source of water for agriculture. Often, the crops from these areas are foods that are consumed nation-wide and even world-wide.

In areas with dry climates, melting snow in the mountains is a critical source of water for agriculture. U.S. Geological Survey Photo (Public Domain)

Because human demand remains fairly constant, agriculture uses a greater proportion of available water in dry years than in wet years, when more water is available for natural ecosystems in California. California Department of Water Resources, California Water Plan Update 2018, on Public Policy Institute of California website.

Generating Electricity

When you flip a light switch or plug in your phone to charge, you might have snow to thank for the electricity that you are using! As snow melts in the mountains, it flows into streams and rivers. In many areas of the world, including the United States, that water is used to generate hydroelectricity. (“Hydro” comes from the Latin word for water.)

Diagram of a hydroelectric dam
Hydroelectricity is generated by harnessing the force from water under the influence of gravity to power a turbine. Illustration from Tennessee Valley Authority / Tomea (CC-BY-SA-3.0)

Hydroelectricity uses the energy of flowing water to turn a turbine, which in turn powers a generator, which converts the energy into electricity. The water that moves the turbine is held in a reservoir created by a large dam, and the turbine and generator are located at the bottom of the dam inside its walls. To generate power, water from the reservoir is released into a chute that drops down inside the dam to turn the turbine blades. The water then flows out of the dam and back into the river, or it may be pumped back into the reservoir to reuse.

Hydroelectric power plants are located throughout most of the United States, with many of the largest plants are located in the Pacific Northwest, where hydro-power accounts for 70% of the region’s electricity. U.S. Department of Energy Image, Office of Energy Efficiency & Renewable Energy, Water Power Technologies Office (Public Domain)

Hydropower provides approximately 17% of the world’s total electricity (USGS, n.d.-b), and in the Pacific Northwest of the United States, a series of dams and power plants in the Columbia River basin generates 70% of the electricity that the region uses. Snow that falls in the Cascade Mountains of Canada, Washington, Oregon, and northern California supplies water to hydroelectric facilities and ultimately to people who might live hundreds of miles downstream.

Hydropower is a renewable energy source and accounted for 70% of renewable energy used in the United States in 2015. Benefits of hydroelectricity include its relatively low cost and the fact that it can respond quickly to changes in demands for electricity throughout the day and the year. Downsides to hydropower can include the flooding of natural areas behind dam sites, barriers to migrating salmon, and destruction of plant and animal habitat above and below the dam.

Human use

Not all water use is as obvious as turning on a faucet. Water is used in manufacturing the items that we use everyday. Paper plants such as this one are a major industrial user of water. U.S. Geological Survey Photo / Alan Cressler (Public domain)

In many locations, people benefit indirectly from snow when they eat foods that have been grown using water from snowmelt (water from melted snow) or use electricity generated by rivers fed by melting snow. Snow also benefits people directly by providing water for everything from drinking and washing to watering lawns and manufacturing.  An estimated 1.2 billion people around the world – approximately 1/6th of the world’s population – uses water from snow melt for human consumption and agriculture.

Las Vegas, NV, gets approximately 90% of its water from Lake Mead, approximately 24 miles away. The Lake exists where the Colorado River is dammed by the 726 foot tall, 660 foot thick (at the base) Hoover Dam, shown here. U.S. Bureau of Reclamation Photo (Public domain)

Las Vegas, Nevada, is an example of a desert city that couldn’t exist in its present size without water from snowmelt in the Rocky Mountains. Southern Nevada only gets about 4 inches of precipitation per year.  In 2018, southern Nevada residents used an average 124 gallons of water per person per day – that’s 46,720 gallons of water per person per year! The population of Las Vegas in 2018 was 644,644, so that means that the city of Las Vegas used more than 30 billion gallons of water in 2018! About 90% of the water that Las Vegas uses comes from the Colorado River, which begins in the high Rocky Mountains where it is fed by melting snow (Las Vegas Valley Water District, n.d.).

Sustaining ecosystems

Red fish underwater in a shallow, rocky stream
Coho salmon, among other species, require cold water to survive and spawn (reproduce). Bureau of Land Management Photo (CC-BY-2.0)

Snow is important for many living things due to its ability to provide insulation, shelter, and moisture in cold environments. Even in areas where it doesn’t snow in the winter, however, melting snow is a critical source of water for sustaining healthy ecosystems downstream.

Snow melt happens slowly as compared to a sudden rainstorm that might flood some areas and/or leave them without enough water later in the summer. Rivers and streams fed by snowmelt provide habitat for many fish and other aquatic species, including cold-water fish such as salmon and trout that cannot survive in warm water temperatures. In turn, these organisms form the foundation of important food webs. For example, in many parts of Alaska, salmon are an important source of food for brown (grizzly) bears.

Water from melting snow also seeps into the ground, providing soil moisture that plants need to grow and reproduce during the summer months. While rain in spring, summer, and fall can also provide moisture, if too much water comes at one time, the soil is not able to absorb it all, so it flows into streams and out of the ecosystem.