FLOOD10416

• County: Statewide
• Title: Historical Perspectives on Colorado Drought
• Date: 12/1/2003
• Prepared For: CWCB
• Prepared By: HDR
• Floodplain - Doc Type: Educational/Technical/Reference Information

Historical Perspectives on Colorado Drought

Trees can grow
to be hundr9ds
to thousands ye.
old and can
contain amuaJly.
resolvQd records
of climate for cenlun9s to mllenia
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The yellow bars indicate the
drought periods in the tree ring
estimated PDSf charts. The red
areas on the accompanying
maps show the areas of
observed drought

2002)

Were a drought of this severity and duration to occur here today or in the future. i
would have. Woodhouse warns us. "considerable impacts now that the area now
includes a major. rapidly expanding metropolitan area as well as large-scale crop and

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Page 7

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Paleo-climatology of Colorado Droughts
Investigation of droughts that pre-dalc the instrumentation period falls within the
realm of paleo- <:lima to logy. One of many options, tree rings can be utilized to
reconstruct records or past climate, including precipitation, drought, stream flow,
and temperature. Trees at mid. to high-latitudes, such as thosc found in Colorado,
grow one ring per year, and thc most reccnt ring is formed inside thc bark.
A weahh oflong.livcd, moisturc-sensitivc trees in this state make possible the
generation of high -quality stream flow reconstructions that extend 300 to over 500
years into the past. Variations in ring widths that arc common from tree to tree
reflect droughts and other anomalies in elimate (Woodhouse 2003).
Having established a gent..'J"3.l understanding of tree ring analysis, we can now look
at some examples of the application oftrec ring studies to dctennine historical
drought periods in Colorado. Woodhouse et al. (2002) provide a detailed account
of the impacts and implications of a drought in the western Great Plains from 1845-
1856. Tree-ring based reconstructions of streamflow and Palmer Drought Severity
Index (PDSI) have been developed and clearly show the extensivc magnitude and
duration of this mid.1911l century drought.
As depicted in Figure 4, the identified core area (the shaded region) of the 1845-
1856 Drought encompassed much of southeastern Colorado and the Front Range.
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(Woodhouse et al.

Figure 4 Core area of 1845-1856 drought

HDR Engineering. Inc.
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