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Water & Energy Cycles

The Colorado River provides the fresh water supply to over 27 million people in 7 states and 2 countries. This supply is projected to decrease by 5-20% over the coming decades due to anthropogenic warming, decreased precipitation, and enhanced evapotranspiration (ET). Recent studies have shown however that dust deposition to snow cover from grazing and agricultural land disturbance that began in the mid 1800s in the Colorado Plateau and Great Basin has been affecting runoff from the Colorado River Basin (CRB). Dust loading during the period 2005 - 2008 shortened snow cover duration by 25 to 35 days through its reduction of snow albedo (enhancement of absorption of solar radiation). The radiative forcing of snowmelt by dust in this region exceeds greenhouse gas forcings by two orders of magnitude. When extended to the entire Upper CRB above Lee’s Ferry, AZ, this modern dust radiative forcing in snow has shifted peak runoff more than 3 weeks earlier and reduced annual runoff by ~5% through enhanced ET. Spring 2009 brought an order of magnitude increase in dust loading to the mountains of the CRB over that observed in 2005-2008. The radiative forcing by this extreme loading had dire impacts on runoff and water management in the basin that resulted in unprecedented early reservoir releases and widespread international media attention. Snow albedo dropped below 0.35 for the last 3 weeks of the season, whereas in previous years, albedos were never consistently below 0.5. The acceleration of snowmelt resulted in the most rapid melt rates in the period of record for SNOTEL sites in most of the Upper CRB. The mean spring radiative forcing by dust in snow was 111 W m-2 relative to the previous range of 25-50 W m-2 and a 48-day reduction of snow cover duration , an additional 20 days over the previous dust impact in 2005-2008. Characterization, modeling, and prediction of this extreme dust-snow interaction and the what we understand to be equilibrium conditions presents a substantial scientific challenge, requiring a multi-disciplinary, integrated, and dynamic Earth System Science approach. Recent events have increased public awareness, and focused the attention of land and water managers on this issue, who are indicating a pressing need for quantitative assessments of dust impacts on CRB hydrology to support management and policy decision-making. Under future climate conditions, assessment and prediction of episodic dust deposition events will provide critical information for efforts to mitigate negative hydrologic impacts on this extremely drought-sensitive region. Based on our record of deposition and forcings, the extreme deposition to the CRB in 2009 represents a vision into the future of hydrologic disturbance in the Colorado River Basin. That this disturbance occurred during the EOS record is fortunate because we now have the greatest capacity to remotely sense dust storms and their source areas, soil moisture, and the radiative forcing of dust in snow. In this project we will use remotely sensed and in situ network observations of dust and snow conditions during the NASA EOS observation period (2000 to present) to develop an integrated observation and modeling system linking synoptic atmospheric conditions, vegetation and soil states in dust emission areas, mountain snowpack dynamics, and basin-scale hydrology. This modeling system will then be applied under future climate and dust mitigation scenarios, providing guidance to land managers and policymakers as to the potential scope of future impacts and mitigation targets. This project, pursued as Fundamental Research, addresses Subelement 1 of the NASA IDS: Integrated Earth System Responses to Extreme Disturbances. Research Components 1-4 will be directly addressed, while informing investigations addressing Research Component 5.

Project PI: Thomas Painter/University of Utah

THE UNIVERSITY OF UTAH COLLEGE OF SOCIAL AND BEHAVIORAL SCIENCE 260 S. CENTRAL CAMPUS DR. RM 205 SALT LAKE CITY, UT 84112

Phone: (801) 581-8730

Fax: (303) 888-7119

Email: painter@geog.utah.edu

http://snow.utah.edu/

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Started: Sep 29, 2010

Last Activity: Jan 05, 2011

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