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08/03/2012

Dust on Snow Impacts Millions in the Desert Southwest

Creek-with-snow-sm_credit Jeff Clay

Photo courtesy Jeff Clay

The Colorado River system flows through the magnificent landscape known as Greater Canyonlands, the area that surrounds Canyonlands National Park in southern Utah.  Greater Canyonlands is a treasure trove of archeological sites, geologic splendor and unparalleled beauty. It deserves special protection for these reasons, but there is another vital factor to consider.  Damage to the desert soils in Greater Canyonlands contributes to red dust that coats mountain snow and decreases the flow of valuable water crucial to life in the American Southwest.

The Colorado River system is the water source for 27 million people in seven western states and Mexico.  It is used to irrigate 3.5 million agricultural acres in the desert Southwest and provides water for large private industries, military bases, cities and wildlife. 

The list of communities that depend on the sacred Colorado River is long.  In the Upper Colorado River Basin, Colorado, Wyoming, Utah and New Mexico rely upon water from the Colorado River.  In Colorado, the cities of Denver, Colorado Springs and more than 40 surrounding communities tap the river for resources.  The headwaters of the Green River, a major tributary of the Colorado River, are in Wyoming and support 30% of the Wyoming’s income and 13% of its people including those living in Rock Springs and Cheyenne.    In Utah, two-thirds of the people are or will be served by water from the Colorado River as the Central Utah Project brings resources to supplement Salt Lake City and communities in 12 counties.  In Utah, five national parks have rivers that are part of the Colorado River System.  In New Mexico, the San Juan River, a tributary of the Colorado River supports the towns of Farmington, Bloomfield and smaller communities and rural areas. 

In the Lower Colorado River Basin, Arizona, Nevada, California, and Mexico rely upon water from the Colorado River. The Colorado River supplies half of what Arizona uses in the Central Arizona Water Project, which carries water into its most populous counties, providing one-third of the water supply of Phoenix and half of the water for Tucson.  In Nevada, Las Vegas Valley relies on the Colorado River to meet its needs.  In California alone, water from the Colorado River supplies the daily needs of more than 15 million people.  The Colorado River Aqueduct brings indispensable water to the multi-billion dollar economies of Los Angeles, San Diego, Long Beach, and Riverside plus about 135 other cities and towns.  On top of this, agricultural and wildlife needs are also met by this water.  

In the American Southwest, the cities, agriculture, industry, thousands of golf courses and swimming pools, and hotel fountains have already sucked the Colorado River dry.  In Mexico, the Colorado River no longer reaches the Sea of Cortez and the Colorado River Delta that Aldo Leopold described as North America’s greatest oasis no longer exists.  Without the water flowing in the Colorado River and its tributaries, life as we know it in the desert Southwest cannot exist.

The 1922 Colorado River Compact governs the allocation of rights to the water and is an interstate agreement among the seven US states in the Colorado River basin.  Unfortunately, these allotments were based on estimates of river flow that came during a time of abnormally high runoff, and resulted in a misunderstanding of what “normal conditions” are for the Colorado River.  Climate change predictions for the desert southwest will see the area become hotter and drier, decreasing the availability of already scarce water that is essential to life in the desert, even as demand for that water grows.

The Colorado River does not exist in isolation from the mountains and lands that surround it.  Rather, the river depends upon the landscape and how we choose to use and manage those lands from which the river originates and through which it flows.  Winter snowfall and the gradual melting of that snow in springtime is the source of the water flowing in the Colorado River system.

In Utah, desert soils are held in place by both physical and biological crusts that prevent the single inch of top soil from blowing away.  Sometimes, it takes years for these crusts to develop, but when they do, they are very effective in preventing erosion and dust storms, even in high winds.  Unfortunately, when the crust is broken by tires from off-road vehicles or other motorized vehicles, excessive livestock grazing, energy exploration and development, or even footsteps, the soil blows with the desert winds into dust storms that can travel for many miles.  In fact, this dust is known to blow onto the snow fields of the Rocky Mountains, coating the snow with red or brown patches of dust. 

Snow coated with dust absorbs more heat from the sun than white snow and consequently melts faster with peak melt about a month sooner than clean snow.   Earlier snowmelt means plants can be active for a longer time and more water will convert to water vapor and move into the atmosphere by evapotranspiration rather than remain as liquid water that flows into the river.

How does this affect water availability in the Colorado River?  When the peak snowmelt occurs earlier, there is about a 5% reduction in water availability, which is more than 250 billion gallons.  This is enough to supply Los Angeles for a year and a half; it is half of what Arizona takes down through its Central Arizona Project; and twice what the city of Denver uses annually for its water supply.  Five percent is a huge amount of water lost to the Colorado River and those that depend upon it for life in the desert! 

It doesn’t have to be this way.  We don’t have to lose this precious water to dust!  Better land management can recover and prevent this water loss.   The best way to reduce windborne dust from soil erosion is to prevent land use that disturbs the soil surface.  When we stop soil disturbance and activities that damage the soil crusts, soil surfaces stabilize.  It can take days or years to reform the crusts depending upon the type of crust that forms in a given area. 

Land Management agencies can prevent off-road vehicle abuse within their Travel Management Plans.  We can better manage when, where, and how energy exploration and development takes place. We can reduce the number of livestock trampling the area.  We can raise awareness of people using these delicate landscapes.  We can ask for special protections of special places, such as the area around Canyonlands National Park, Greater Canyonlands.

Permanent Protection for Greater Canyonlands through national monument or other designations would not only preserve the beautiful canyons and unique wildlife, it would be a step toward mitigating the deposition of dust-on-snow that has reduced flows in the Colorado River.  It is a means of mitigating the water sources for millions of Americans and communities throughout the Southwest.

-- By Marion Klaus 

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