Disturbed Desert Dust and Early Snowmelt

How We Lose 18-Months-Worth of Water for Los Angeles Every Year

A recent scientific study has found that the Colorado River is losing 35 billion cubic feet a year due to early snowmelt caused by the deposition of windborne dust in the mountains of the Upper Colorado River Basin.  That is enough water to supply Los Angeles for eighteen months!

The study, “Response of Colorado River Runoff to Dust Radiative Forcing in Snow,” reports on research by Dr. Thomas Painter of the NASA Jet Propulsion Laboratory and a team of scientists.  In a nutshell, it explains the following: 

Wind storms pick up desert soils from the Colorado Plateau and Great Basin that have been disturbed by activities such as “grazing, drought, fire, plowing, or vehicles” and deposit it on mountain snow pack throughout the Upper Colorado River Basin.  When that dust lands on snow it causes enhanced absorption of solar radiation—just like wearing a dark t-shirt outside on a hot sunny day.  Amazingly, dust is being deposited at rates approximately five times those of the era predating European settlement.  Read more about this on our website.

Using computer modeling, Painter’s team found peak runoff at Lees Ferry on the Colorado River near the Utah/Arizona border occurs on average three weeks earlier than it would without the impact of this dust.  They also determined annual runoff is decreased by 5 percent on average compared to pre-European settlement levels due to evapotranspiration (water transpiring from plants and soils which normally would not be exposed yet) and snow sublimation (snow turning to water vapor).  This loss adds up to over 1 billion cubic meters, or around 35 billion cubic feet, of water a year.

What can be done about this?  As the article explains, stopping those activities that lead to soil disturbance generally results in the stabilization of soils.  Stabilized soils result in less dust and, therefore, longer snowpack life.

Because the Bureau of Land Management (BLM) manages such vast tracts of land on the Colorado Plateau and Great Basin, the agency could make a significant contribution to dust reduction if it reconsidered some of its current land management practices.  BLM needs to assess the true toll that soil disturbing activities such as ORV use, grazing, and energy development are having on our public water supply.  Action is sorely needed because, as the study’s author’s point out, various models predict that climate change will cause a 7 to 20 percent reduction in current runoff in the Colorado River Basin.

Wilderness protection, like that proposed in America’s Red Rock Wilderness Act, would be one step in the right direction, because such protection would prevent some soil-disturbing activities in the Colorado Plateau and Great Basin.  Fixing the BLM’s unbalanced and harmful resource management plans that were recently completed for the Colorado Plateau—which, among other things, designated over 20,000 miles of dirt trails for vehicle use—would also be a step towards addressing this problem.