In the past five years, scientific studies estimated declines of future flows ranging from 6 percent to 45 percent by 2050. A paper by University of Washington researchers and co-authors at eight institutions across the West aims to explain this wide range, and provide policymakers and the public with a framework for comparison. The study is published this week in the Bulletin of the American Meteorological Society.
"The different estimates have led to a lot of frustration," said lead author Julie Vano, who recently earned a UW doctorate in civil and environmental engineering. "This paper puts all the studies in a single framework and identifies how they are connected."
Besides analyzing the uncertainty, the authors establish what is known about the river's future. Warmer temperatures will lead to more evaporation and thus less flow. Changes to precipitation are less certain, since the headwaters are at the northern edge of a band of projected drying, but climate change will likely decrease the rain and snow that drains into the Colorado basin.
It also turns out that the early 20th century, which is the basis for water allocation in the basin, was a period of unusually high flow. The tree ring record suggests that the Colorado has experienced severe droughts in the past and will do so again, even without any human-caused climate change.
"The Colorado River is kind of ground zero for drying in the southwestern U.S.," said co-author Dennis Lettenmaier, a UW professor of civil and environmental engineering. "We hope this paper sheds some light on how to interpret results from the new generation of climate models, and why there's an expectation that there will be a range of values, even when analyzing output from the same models."
The authors include leaders in Western water issues, ranging from specialists in atmospheric sciences to hydrology to paleoclimate. Other co-authors are Bradley Udall at the University of Colorado in Boulder; Daniel Cayan, Tapash Das and Hugo Hidalgo at the University of California, San Diego; Jonathan Overpeck, Holly Hartmann and Kiyomi Morino at the University of Arizona in Tucson; Levi Brekke at the federal Bureau of Reclamation; Gregory McCabe at the U.S. Geological Survey in Denver; Robert Webb and Martin Hoerling at the National Oceanographic and Atmospheric Administration in Boulder; and Kevin Werner at the National Weather Service in Salt Lake City.
• Methods used to downscale from the roughly 200-kilometer resolution used by global climate models to the 10- to 20-kilometer resolution used by regional hydrology models.
While the paper does not determine a new estimate for future flows, it provides context for evaluating the current numbers. The 6 percent reduction estimate, for example, did not include some of the fourth-generation climate model runs that tend to predict a dryer West. And the 45 percent decrease estimate relied on models with a coarse spatial resolution that could not capture the effects of topography in the headwater regions. The analysis thus supports more moderate estimates of changes in future flows.
"Drought and climate change are a one-two punch for our water supply," said Overpeck, a professor of geosciences and of atmospheric sciences at the University of Arizona.
The new paper is intended to be used by scientists, policymakers and stakeholders to judge future estimates.
"I hope people will be able to look at this paper and say, 'OK, here’s the context in which this new study is claiming these new results,'" Vano said.
The research was funded by NOAA through its Regional Integrated Sciences and Assessments program and its National Integrated Drought Information System.For more information:
Hannah Hickey | Newswise
Monitoring lava lake levels in Congo volcano
16.05.2018 | Seismological Society of America
Ice stream draining Greenland Ice Sheet sensitive to changes over past 45,000 years
14.05.2018 | Oregon State University
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology