PUB00155

• Year: 2007
• Title: The Colorado River The Story of a Quest for Certainty on a Diminishing River
• CWCB Section: Administration
• Author: Eric Kuhn
• Description: The Colorado River The Story of a Quest for Certainty on a Diminishing River
• Publications - Doc Type: Other

The Paleohydrologic Record

Our gage record is relatively recent. There was no gage at Lee Ferry until 1921. In the Upper
Basin the longest serving big river gages are the Green River at Green River, Utah which has been
in place since 1894 and the Colorado River near Cisco, Utah gage, 1913 to present.

As noted by a number of hydrologists, our stream flow records and thus reconstructed
natural flows before 1930 are relatively crude.15t Reclamation and others have used a number of
methods, primarily statistical correlations, to reconstruct the record. The limited gage records are not
the only problem. Knowing the amounts of lands under irrigation and crops being irrigated is also
necessary to reconstruct natural flows. These records are also less reliable, the farther we go back.
The bottom line is that we must recognize that much of the so-called gage record is actually a
synthetic record with considerable uncertainty.

In March 1976 Charles Stockton and Gordon Jacoby published "Long-Term Surface-Water
Supply and Stream Flow Trends in the Upper Colorado River Basin." The Stockton and Jacoby
report was one of a number of studies funded by the National Science Foundation. The effort was
called the Lake Powell Research Project.

Stockton and Jacoby used dendrochronology to reconstruct a longer term (1512 to 1961)
hydro graph of the Colorado River at Lee Ferry.152 The report concluded that the long term natural
flow at Lee Ferry was only 13.5 maf + .5 maf. The Stockton and Jacoby reconstructions were used
for the Severe and Sustained Drought on the Colorado River Project. The results of this project were
published by the Water Resources Bulletin, Journal of the American Water Resources Association,
October 1995.153

After the Stockton Jacoby report there have been a number of additional tree ring based
reconstructions. Most recently, in 2006 Connie Woodhouse, Stephen Gray and David Meko
published "Updated Stream Flow Reconstruction for the Upper Colorado River Basin" in 2006.154

The January 2007 National Academy of Sciences report has a good discussion on
uncertainties in stream flow reconstructions. 155 The report concludes that despite the differences, all
of the reconstructions share important and common conclusions:

1. The long term average natural flow at Lee Ferry is less than the USBR 1905-2000
natural flow data base. The means are in the 13.0 maf/year to 14.7 maf/year range.

151Tipton & Kalmbach, page 9.

152 A detailed discussion of dendrochronology is found on pages 11-17 of the Stockton and Jacoby report. The bottom line is that the
statistical methods used in dendrochronology are no different and probably more sophisticated than the methods used to recreate the
USBR natural flow data base.

153Unfortunately, the report was published during a very wet period and did not receive the attention it deserved by policy makers.
Copies of the journal can be obtained from Hydrosphere Inc. ",,"\\w.hvdrosphere.com

154The paper was published by Water Resources Research, Volume 42, January 2006.

155National Academy of Sciences, pages 75-76.

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