Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Historic Colorado River streamflows reconstructed back to 1490

29.05.2006


A new tree-ring-based reconstruction of 508 years of Colorado River streamflow confirms that droughts more severe than the 2000-2004 drought occurred before stream gages were installed on the river.


On July 21, 2004, the reservoir is 60% empty after 5 years of drought. New research shows that prior to 1900, the Colorado River basin may have had as many as eight droughts as severe as the 2000-2004 drought. Credit: Brad Udall.



The new research also confirms that using stream gage records alone may overestimate the average amount of water in the river because the last 100-year period was wetter than the average for the last five centuries.

"This work updates the original landmark Colorado River reconstruction that was done at The University of Arizona’s Laboratory of Tree-Ring Research," said David M. Meko, a UA associate research professor of dendrochronology, the science of tree-ring dating.


"The main points of the 1976 research hold up. Droughts more severe and intense than we’ve seen in the gaged record occurred in the past, and the long-term mean flow is lower than the gaged mean flow."

Connie A. Woodhouse said, "The updated reconstruction for Lee’s Ferry indicates that as many as eight droughts similar in severity, in terms of average flow, to the 5-year 2000-2004 drought have occurred since 1500."

Woodhouse, who led the research team, is a physical scientist at the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center Paleoclimatogy Branch in Boulder, Colo.

Allocations of Colorado River water made in the 1922 Colorado River Compact between the states of Arizona, California, Colorado, Nevada, New Mexico, Wyoming and Utah therefore overestimate the amount of river water available. Los Angeles, Las Vegas, Denver, Phoenix, Tucson and Albuquerque are among the many cities dependent on Colorado River water.

"The long-term perspective provided by tree-ring reconstructions points to a looming conflict between water demand and supply in the upper Colorado River basin," the researchers wrote in their report.

Woodhouse and Meko collaborated with Stephen T. Gray of the U.S. Geological Survey in Tucson, Ariz., and Jeffrey Lukas of the Institute of Arctic and Alpine Research at the University of Colorado in Boulder. The team’s research article, "Updated streamflow reconstructions for the Upper Colorado River Basin," is published in the May 2006 issue of Water Resources Research.

Funding for the study was provided by NOAA, USGS, the U.S. Bureau of Reclamation, the University of Arizona Water Sustainability Program and the University of Colorado Western Water Assessment.

The new research updates the first tree-ring based reconstruction of streamflows at Lee’s Ferry and other Colorado River basin gages, which was published in 1976. The new research improves on the previous work by using an expanded network of tree-ring sites, and because the scientists could incorporate an additional 34 years of tree-ring records to compare to the stream gage record for four gages in the Upper Colorado River basin.

Researchers were able to statistically recreate flows back four centuries prior to the gage record by comparing tree-ring widths from 1906 to 1995 with naturalized gaged streamflows (i.e., streamflows adjusted to remove the impacts of humans) during the same period. The streamflows were reconstructed by using cores taken from approximately 1,200 trees in 60 locations throughout the Colorado River basin area.

Streamflow was reconstructed for Lee’s Ferry, Ariz., a critical measuring location and the dividing point between the Upper Basin and the Lower Basin of the Colorado River as defined by the 1922 Colorado River Compact.

The Lee’s Ferry streamflows are of particular interest to water managers in California, Arizona, Nevada, Utah, New Mexico, Wyoming and Colorado, the seven signatory states to the Compact, because the Colorado River supplies drinking water to approximately 30 million people and irrigates 3.5 million acres of farmland. Historic stream flows for other tributaries to the Colorado River were reconstructed as well.

The underlying message from these new reconstructions remains the same: that Colorado River Compact allocations were based on one of the wettest periods in the past five centuries, and that droughts more severe than any in the last 100 years occurred before stream gages were installed. The most severe sustained drought (based on the lowest 20-year average) in the Upper Colorado River basin occurred in the last part of the 16th century. This reconstruction also shows that average annual flows on the Upper Colorado regularly vary from one decade to the next by more than 1 million acre-feet.

According to Eric Kuhn, general manager of the Colorado River Water Conservation District and an expert on Colorado River issues, "Water managers have always made critical water decisions based on a relatively short and often incomplete gaged record for the Colorado River. This study should be of keen interest because it shows that there were likely a number of long-term droughts more severe than what we experienced in the 1900s and during this century. The study should have enormous implications on how the river is managed."

The new reconstructions do indicate the river may have a higher long-term average flow, 14.6 million acre-feet, than did the 1976 reconstruction, which estimated a long-term average flow of 13.5 million acre-feet. However, the new average for the past 500 years is still lower than the average of 15.2 million acre-feet recorded by stream gages from 1906 to 1995. An acre-foot is approximately 325,000 gallons and is enough water to meet the needs of two four-person families for a year.

The scientists’ next step is understanding the source of the differences in the means between the new reconstruction and the 1976 work.

Mari N. Jensen | EurekAlert!
Further information:
http://www.arizona.edu
http://www.ltrr.arizona.edu
http://www.uawater.arizona.edu/

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling 'fast fashion' to reduce waste and pollution
03.04.2017 | American Chemical Society

nachricht Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>