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 Perspectivos on Colorado Drought

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regional drought occurrence. An ex.tensive review by the Colorado Climate Center
on drought's cyclicity was inconclusive. So can you believe what you want'?
An example of how new information can be developed through "database mining"
can be seen in Table 6. Table 6 shows a comparison from 1900 to 1999 of decadal
occurrences of basin-spcci fie annual precipitation that is 2 inches or more above or
below average. The base annual precipitation information was derived from Western
Regional Climate Center database. Let's look at two fresh approaches to viewing the
information

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Tobie 6: Comparison of the Number of Annual Basin Precipitations +/-
Average/Decade

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A = Years with annual basin
precipitation of equal to or
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B = Years with annual basin
precipitation of equal or
greater value than 2" below
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Figure 21 - Comparison of the difference between the numbers of annual basin
precipitation years. 2" above and 2" below average summed by decade and by basin.

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Table 6 shows some interesting basin-specific information but let's concentrate for
the moment on the big picture. The droughts of the 1930's. 1950's and the 1970's
show up signilicant decades of below average precipitation in Colorado's major river
basins. Wet periods also show up clearly. Note the drought of the 1950's was not
"as sync" from basin to basin as during the othcr droughts. Of equal importance is
the plotting of the deeadal changes from basin to basin as shown in Figure 7.

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