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<br />4-02. Climate.
<br />
<br />a. General. Wide variations of climate occur in the
<br />Arkansas Basin above the Pueblo Dam. In the lIIOuntainous regions
<br />of the headwaters, precipitation varies widely over relatively
<br />short distances. It varies from 10 inches annually in some locations
<br />to 40 inches annually over limited areas. Much of the total pre-
<br />cipitation at the higher elevations is in the form of snow. Runoff
<br />from snowmelt constitutes s 'dependable water supply for municipal,
<br />irrigation, industrial, and other uses. The majority of snowmelt
<br />runoff occurs during the period May, June, and July. In the plains
<br />region, IIIOst of the precipitation is in the form of rainfall.
<br />At times, the occurrence is in the form of violent cloudbursts
<br />which cause flash floods of short durations and small volumes, but
<br />of damaging intensities. Hore than 80 percent of the everage annual
<br />precipitation on the plains occurs during the period April through
<br />October.
<br />
<br />b. Precipitation. Recorded annual precipitation normals
<br />within the watershed vary from 19.21 inches at WetlllOre to 9.26
<br />inches at Twin Lakes Reservoir. During the 6-month period, April
<br />through September, Wetmore receives 65 percent of the annual normal
<br />precipitation, and Twin Lakes Reservoir receives 63 percent of the
<br />annual normal precipitation. The maximum rainfall IIIOnths are May
<br />and July through IIIOst of the basin. Thunderstorm activity is great-
<br />est in July with an average of 13 days at Pueblo. A maximum
<br />observed-day precipitation of 6.10 inches occurred at Rye, Colo-
<br />rado, in May 1955. TI\e June 1965 storm produced a maximum 24-hour
<br />precipitation amount of 11.08 inches at Holly, Colorado. The mean
<br />annual snowfall alllOunts vary from 146 inches at Lake '~~raine to
<br />:l3 inches at Canon City. Pusblo Weather Ssrvice at the airport
<br />has had a maximum lIIonthly snowfall of 29.3 inches, anu a maximum
<br />~:4-hour snow fell of l6. B inches. The average monthly anu annual
<br />precipitation normals for representative weather Htations in the
<br />Arkansas watershed above Pueblo are tabulated in Table 4-l, anu
<br />the maximum observed-day precipitation is shown in Table 4-2.
<br />Locations of weather stations are shown on Plate 4-2.
<br />
<br />c. Temperatures. The wide variation of temperatures
<br />is due principally to the variation in altitude. Leadville, at
<br />elevation 10,177 feet m.s.l., has a mean annual maximum and minimum
<br />temperature of 50.7 and 21.9 degrees fahrenheit, respectively;
<br />whereas Pueblo, at elevation 4,700 feet m.s.l., has a mean annual
<br />maximum and minimum temperature of 68.0 and 37.3 degrees fahrenheit,
<br />respectively. Extreme temperatures have ranged from 105 degrees
<br />fahrenheit at Pueblo to a -54 degrees fahrenheit at Westcliffe,
<br />elevation 7,860 feet m.s.l. The average last-spring occurrence of
<br />
<br />4-2
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