May 5 2010
From The Space Library
RELEASE: 10-229
NASA FUNDED STUDY SHOWS DESERT DUST CUTS COLORADO RIVER FLOW
WASHINGTON -- Snow melt in the Colorado River basin is occurring earlier, reducing runoff and the amount of crucial water available downstream. A new study shows this is due to increased dust caused by human activities in the region during the past 150 years. The study, led by a NASA scientist and funded by the agency and the National Science Foundation (NSF), showed peak spring runoff now comes three weeks earlier than before the region was settled and soils were disturbed. Annual runoff is lower by more than five percent on average compared to pre-settlement levels. The findings have major implications for the 27 million people in the seven U.S. states and Mexico who rely on the Colorado River for drinking, agricultural and industrial water. The results were published in this week's Proceedings of the National Academy of Sciences. The research team was led by Tom Painter, a snow hydrologist at both NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the University of California at Los Angeles. The team examined the impact of human-produced dust deposits on mountain snowpacks over the Upper Colorado River basin between 1915 and 2003. Studies of lake sediment cores showed the amount of dust falling in the Rocky Mountains increased by 500 to 600 percent since the mid-to-late 1800s when grazing and agriculture began to disturb fragile but stable desert soils. The team used an advanced hydrology model to simulate the balance of water flowing into and out of the river basin under current dusty conditions and those that existed before soil was disturbed. Hydrologic data gathered from field studies funded by NASA and NSF and measurements of the absorption of sunlight by dust in snow were combined with the modeling. More than 80 percent of sunlight falling on fresh snow is typically reflected back into space. In the semi-arid regions of the Colorado Plateau and Great Basin, winds blow desert dust east, triggering dust-on-snow events. When dark dust particles fall on snow, they reduce its ability to reflect sunlight. The snow also absorbs more of the sun's energy. This darker snow cover melts earlier, with some water evaporating into the atmosphere. Earlier melt seasons expose vegetation sooner, and plants lose water to the atmosphere through the exhalation of vapor. The study shows an annual average of approximately 35-billion cubic feet of water is lost from this exhalation and the overall evaporation that would otherwise feed the Colorado River. This is enough water to supply Los Angeles for 18 months. "The compressed mountain runoff period makes water management more difficult than a slower runoff, Painter said. With the more rapid runoff under dust-accelerated melt, costly errors are more likely to be made when water is released from and captured in Colorado River reservoirs. Prior to the study, scientists and water managers had a poor understanding of dust-on-snow events. Scientists knew from theory and modeling studies that dust could be changing the way snowfields reflect and absorb sunlight, but no one had measured its full impact on snowmelt rates and runoff over the river basin. The team addressed these uncertainties by making systematic measurements of the sources, frequency and snowmelt impact of dust-on-snow events. "These researchers brought together their collective expertise to provide a historical context for how the Colorado River and its runoff respond to dust deposition on snow, said Anjuli Bamzai, program director in NSF's Division of Atmospheric and Geospace Sciences in Arlington, Va. The work lays the foundation for future sound water resource management. Painter believes steps can be taken to reduce the severity of dust-on-snow events in the Colorado River basin. He points to the impact of the Taylor Grazing Act of 1934 for potential guidance on how dust loads can be reduced. The act regulated grazing on public lands to improve rangeland conditions. Lake sediment studies show it decreased the amount of dust falling in the Rocky Mountains by about one quarter. "Restoration of desert soils could increase the duration of snow cover, simplifying water management, increasing water supplies and reducing the need for additional reservoir storage of water. Peak runoff under cleaner conditions would then come later in summer, when agricultural and other water demands are greater, Painter said. It could also at least partially mitigate the expected regional impacts of climate change, which include reduced Colorado River flows, increased year-to-year variability in its flow rate and more severe and longer droughts, he added. Climate models project a seven to 20 percent reduction in Colorado River basin runoff in this century due to climate change. Other institutions participating in the study include the National Snow and Ice Center in Boulder, Colo.; U.S. Geological Survey Southwest Biological Center in Moab, Utah; University of Washington in Seattle; Center for Snow and Avalanche Studies in Silverton, Colo.; and the University of Colorado-NOAA Western Water Assessment in Boulder.
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MEDIA ADVISORY: M10-073
NASA TV CARRYING SPACE STATION CREW LANDING AND NEXT CREW'S LAUNCH
HOUSTON -- NASA Television will cover the June 1 return to Earth of three International Space Station crew members and the June 15 launch of the newest trio of station residents. The new crew will be the 24th to live and work on the orbiting laboratory. Expedition 23 Soyuz Commander Oleg Kotov, NASA Flight Engineer T.J. Creamer and Japan Aerospace Exploration Agency Flight Engineer Soichi Noguchi are scheduled to land their Soyuz TMA-17 spacecraft June 1 on the southern region steppe of Kazakhstan, completing almost six months on the station. On June 15, Russian cosmonaut Fyodor Yurchikhin and NASA Flight Engineers Doug Wheelock and Shannon Walker will launch on the Soyuz TMA-19 from the Baikonur Cosmodrome in Kazakhstan. They will dock to the station June 17, joining Expedition 24 Commander Alexander Skvortsov, NASA Flight Engineer Tracy Caldwell Dyson and Russian Flight Engineer Mikhail Kornienko, who have been aboard the station since April 4. Upcoming NASA TV broadcasts of these events and surrounding activities include (all times CDT): 1-Jun 10 a.m. -- ISS Update commentary hour that includes a replay of the May 31 change of command ceremony aboard the station, in which Kotov will hand over command of the station to Skvortsov. The ceremony also will be replayed during landing coverage 3:30 p.m. -- Coverage of Expedition 23 farewells and hatch closure, scheduled at 3:50 p.m. 6:45 p.m. -- Coverage of Expedition 23 undocking from station, scheduled at 7:08 p.m. 9:15 p.m. -- Coverage of deorbit burn, scheduled for 9:37 p.m., and landing in Kazakhstan, scheduled for 10:27 p.m. 2-Jun 11 a.m. -- Video File of post-landing activities, including interviews with Creamer and Noguchi 3-Jun 11 a.m. -- Video File of Expedition 24 farewell activities at the Gagarin Cosmonaut Training Center 11-Jun 11 a.m. -- Video File of Expedition 24 prelaunch activities in Baikonur 13-Jun 11 a.m. -- Video File of activities in Baikonur, including Soyuz rocket mating and rollout to the launch pad 14-Jun 4 p.m. -- Video File of the final prelaunch news conference and Russian State Commission Meeting in Baikonur 15-Jun 3 p.m. -- Video feed of Expedition 24 crew's final prelaunch activities in Baikonur 3:45 p.m. -- Coverage of launch from Baikonur, scheduled for 4:35 p.m., and replays 7 p.m. -- Video File of prelaunch activities, launch and postlaunch interviews from Baikonur 17-Jun 5 p.m. -- Coverage of Soyuz docking to station, scheduled at 5:34 p.m., and post-docking news conference from Korolev, Russia 8:15 p.m. -- Hatch opening, scheduled at 8:34 p.m., and welcome ceremony 11 p.m. -- Video File of docking, hatch opening and welcome ceremony Operational activity could result in some changes to the programming schedule. For NASA TV streaming video, downlink and schedule information, visit: http://www.nasa.gov/ntv
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