FLOOD10136

• Designation Number: 114
• County: Chaffee
• Community: Poncha Springs
• Stream Name: South Arkansas River/Poncha Creek
• Basin: Arkansas
• Title: FIR - South Arkansas River/Poncha Creek, Poncha Springs, CO
• Date: 3/1/1978
• Designation Date: 11/1/1978
• Prepared By: WRC, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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features are typical of a mountain valley on an eastern slope near the

central port~on of a large continent. They include low prec1p1~ation,

low humidity, abundant sunshine, a wide daily temperature range, and

generally low winds. The surrounding mountains act as a barrier prevent-

ing the northern cold air or eastern storms from penetrating the Upper

Arkansas River Valley.

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CHAPTER III

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HISTORY OF FLOODING

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Streamflow records are available at locations near and within the
study reaches. Recorded historical flows show maximum discharges of
1,110 and 307 cfs for the South Arkansas River at Poncha and Poncha Creek
at Poncha Streamflow Recording Stations. These flows were recorded on
July 5, 1911 and May 27, 1912, respectively. Long term streamflow records
from nearby stations indicate that peak flows occurred in a number of
years, particularly in 1957.

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The records at the Salida weather station, elevation 7060 feet, show

an average annual precipitation of 10.87 inches. precipitaiton varies

at Salida from less than 8 inches in one year out of six to over 15 inches

in one year out of six. The highest recorded annual precipitation was

17.92 inches in 1961. This was followed by the lowest annual precipitation

on record, 4.91 inches in 1962. The monthly distribution of precipitation

varies considerably from one year to the next. Dry months (less than one-

quarter inch of precipitation) are rare for April, July and Augus,t. Wet

months (more than 2 inches precipitation) occur about one in four years in

July, one in five years in April and August. Summer thunderstorms account

for almost 59 percent of the annual precipitation, and account for local

high flows. Hail falls occasionally in the study area.

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The documentation of the peak flows in the study area included:
research of the past issues of Salida newspapers, personal interviews
with the local residents who have resided in the area for a long period,
discussions with the city and county officials, and a written solicitation
from the Colorado Water Conservation Board requesting input from a number
of local residents who were identified by the local officials as possible
sources of information on the history of flooding of the South Arkansas
River and Poncha Creek.

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Summers are cool in the study area with temperatures reaching into the

90's a few times each summer. A maximum temperature of 1000 F was recorded

in August 1902. Temperatures for the summer nights usually drop below

500 F. Winter temperatures, particularly in the daytime, are usually

warmer than those found at similar or lower elevations. Periods of extreme

c~ld temperatures are of short duration. The lowest temperature recorded

at Salida was 3D' F below zero 1n January 1919. The average annual tempera-

ture is 46.50 F , and the average summer temperature is 62.6'F. The average

frost free period is approximately 107 days.

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The research of the past 1ssues of the
Mailll were centered around specific dates.

Salida newspaper "Mountain

These dates were selected from

eleven streamflow gaging stations

dates include:

a review of a graph of peak flow data for
near the study area. Specifically, these

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May 21, 1901

July 8, 1952

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Because of the climatic conditions, the irrigated land in the vicinity

of the study area is in meadows, native hay, and alfalfa. The area is better

adapted to livestock production as compared with farming. Dryland farming

is almost nonexistent in the upper reaches of the Arkansas River Basin.

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June 5, 1911

June 29, 1957

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June 12, 1921

July I, 1957

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July 17, 1923

June 6, 1958

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June 16, 1924

June 20, 1965

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June 21, 1947

July 13, 1965

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June 10, 1952

June 11, 1973

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