WSP01635

• File Number: 8200.400
• Description: Colorado River Basin - Briefing Documents-History-Correspondence
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/1/1961
• Author: CSU Civil Engineerin
• Title: Analysis of Precipitation Data in the Upper Colorado River Basin
• Water Supply Pro - Doc Type: Report/Study

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I. INTRODUCTION

Work at Colorado State University has been
concerned with analyses of existing climatological
data in order to provide a refinement of basic data
useful in hydrologic studies of the Upper Colorado
River Basin.

Climatological data from many stations in
the Upper Colorado River Basin have been collected
for many years by unpaid cooperative observers of
the U. S. Weather .Bureau. Records of daily maxi~
mum and minimum temperatures. precipitation,
snowfall, and other data are available for about 50
to 60 years prior to 1960. Since 1948 the Weather
Bureau has placed all such data on IBM cards for
machine tabulation and analysis. Prior to 1948
however. climatological data were in tabular form
only. not in a format suitable for machine com-
putation and analysis.

The general procedure followed in this study
has been to place weather records prior to 1948 on
IBM cards in a format suitable for machine com-
putation and analysis as a first step study. These
data were reduced to storm totals and from the re-
duced storm totals various frequency analyses were
performed. Details of the procedures followed in
processing the precipitation data are included in the
appendix.

A, WEATHER STATIONS ANALYZED

Precipitation data from 30 stations in an near
the Upper Colorado River Basin were analyzed in
this study. Table I summarizes the stations and
years included in this analysis. As shown in Table I
about 608,000 cards were used in the analysis. Of
these cards, about 470,000 were prepared at Colo-
rado State University as a part of this study.

TABLE I

The locations of the stations used in this
study are shown in Figure 1. Figure 1 also shows
the inclusive dates for which data were available
for this study.

It should be noted that some parts of this re-
port (such as parts of III and IV) are based on ana-
lyses from stations from Colorado only. since they
were performed by hand prior to the availability of
machine-processed data from all stations.

B. WHEN AND WHERE PRECIPITATION OCCURS

Fall rains. winter snows, and summer
showers are the precipitating mechanisms which
produce the water which runs back toward the ocean
in the Colorado River from the collection basin of
the Colorado River Watershed. This general con-
cept of timing is an oversimplification when applied
to individual stations, but the stream flow of the
Colorado River at Lee Ferry is an integrated
measure of the runoff yield of a large area. This
watershed area is characterized by having rather
extreme variations in elevation, distances from
major moisture sources, and the localized effects
of surrounding terrain and windward exposure of
the locations where precipitation amounts have
been measured.

The pattern of monthly precipitation amounts
is shown in Figure 2 for three groupings of stations
representing three general elevation levels. Rather
uniform timing is indicated at all three levels. The
months of November and June stand out as low
average months, with June being the lowest month
in the entire year. September is a relatively low
month, which tends to divide the summer shower
period from the fall rain period.

SUMMARY OF CARD PUNCHING COMPLETED
Number Of STATION-YEARS
Stations In Stations punched By Total
CSU USWB
Colorado
Western Slope 18 839 170 1,009
Fort Collins I 70 70
New Mexico 1 42 12 54
Utah 5 113 137 250
Wyoming 5 219 58 277
- - -
Total Station-Years 1,283 377 1,660
Total Number of Cards (Approximately) 470,000 138,000 608,000