Colorado River Basin Focus Area Study: Snowpack Hydrodynamics

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The Focus Area Study examined factors affecting snowpack distribution, snowmelt, and losses of snowpack water due to sublimation in the Upper Colorado River Basin. Also, as part of the FAS, the USGS has developed methods to make physical measurements of snowpack sublimation.

National Water Census  •  Colorado River Basin  •  Evapotranspiration  •  Snowpack  •  Water Use  •   Groundwater Discharge 

 

National water census focus area study: colorado. snow station

Meteorological and continuous sublimation monitoring station, Upper Colorado River Basin (Credit: David Clow, USGS)

Understanding the spatial distribution of snowpack water content is essential for forecasting annual runoff in the Upper Colorado River Basin (UCRB). As part of the Colorado River Basin Focus Area Study (CRB FAS), the USGS conducted studies of factors affecting snowpack distribution, snowmelt, and losses of snowpack water due to sublimation in the UCRB.

The USGS has compared the output from the National Weather Service’s Snow Data Assimilation (SNODAS) program (National Operational Hydrologic Remote Sensing Center, 2004) to field-based measurements at multiple locations in the UCRB. Additionally, the USGS installed stations for making physical measurements of snow sublimation and developed spatially distributed estimates of sublimation using a physically-based snow model. Lastly, long-term trends of dust deposition in the Rocky Mountains were evaluated using USGS snow chemistry network observations and were used to evaluate the drivers of changing snowmelt timing.

Results of these studies and ongoing work will help improve runoff forecast models used by water managers in the Western United States.

 

Key Findings and Results

  • Peak snow water equivalent (SWE) in Colorado is occurring 2–3 weeks earlier than it did during the late 1970s, and snowmelt timing has accelerated 7–18 days from 1993 - 2014 primarily due to changes in snowfall and dust deposition.
  • Continuous measurements of snow sublimation at multiple sites were developed and indicate a seasonal loss of 2–30 percent of annual SWE, depending on a variety of conditions including land cover, elevation, aspect, temperature, and wind speed.
  • A spatially distributed snow model simulated sublimation losses to the atmosphere equivalent to 28% of winter precipitation and highlighted that the highest relative sublimation fluxes occurred during the lowest snow years.

 

National Water Census  •  Colorado River Basin  •  Evapotranspiration  •  Snowpack  •  Water Use  •   Groundwater Discharge