WSP05071

• File Number: 8146.400
• Description: Pueblo Dam - Reports
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 10/1/1994
• Author: US Geological Survey
• Title: Use of Frequency Analysis and the Extended Streamflow Prediction Procedure to Estimate Evacuation Dates for the Joint-Use Pool of Pueblo Reservoir Colorado
• Water Supply Pro - Doc Type: Report/Study

-C"~
'.l 'J"':)
Table 1. Streamnow-gaging stations used in the frequency analysis of nacorded daily mean discharges
SlaUon Drainage area Period ot record1 Number of Generalized
Station name ya.ra used In ok..
number (lquora mlleo) (wotar yea,) anaryel. coelflclont'
07094500 Arkansas River at Parkdale 2,548 1946-55; ]965- 36 -0.130
07096000 Arkansas River at Canon City 3,117 1889- 395 ..121
07097000 Arkansas River at Portland 4,024 1940-52; 1975- 29 . .108
07099200 Arkansas River near Ponland 4,280 1966-74 9 -.106
07099400 Arkansas River above Pueblo 4,670 1966- 25 -.104
07099500 Arkansas River near Pueblo 4,686 1895-1975 '79 -.104
07106500 Fountain Creek at Pueblo 926 1923-25; 1941-65; 45 - .102
1972-
407108500 51. Charles River near Pueblo 467 1941-53 13 - .102
407108800 51. Charles River near Vineland 473 1968-74 7 - .102
407108900 St. Charles River at Vineland 474 1979- 12 - .102
"07109000 St. Charles River at mouth near Pueblo 482 1923-25 4 - .102
07109500 Arkansas River near Avondale 6,327 1940-51; 1966- 38 - .102

IRccords through water year 1990 were used in frequency analysis; no ending year indicates station was operating at the beginning of water year
t991.
lGeneralized skew coefficient detennined from U.S. Interagency Advisory committee on Water Data (1982) map by frequency-analysis computer
program (Kirby, t981).
30ata for some years prior to 1910 were excluded because daily mean discharges were not available.
"'The four 51. Charles River stations we~ combined for the frequency analysis; combined record length is 36 years.

used in the frequency analysis to include any substan-
tial trends in the discharges during a more extended
time period.

The frequency analysis had two objectives:
(I) To derive the estimated daily mean discharges at the
0.01 EP (hereinafter referred to as 0.01 EP discharges)
flowing into Pueblo Reservoir during April ]5-May 14,
and (2) to derive 0.01 EP discharges for April 15-
May 14 for tributaries downstream from the reservoir.
The downstream analysis was needed because oflimits
in the channel capacity of the Arkansas River in the
vicinity of Avondale (fig. 1). The U.S. Army Corps of
Engineers (1977) detennined that discharge in this area

should not exceed about 6,000 ifls and that Pueblo
Reservoir should be operated, if possible, to prevent
exceeding that discharge at station 07 I 09500 Arkansas
River near Avondale (hereinafter referred to as "the
near-Avondale" station). Discharges in Fountain Creek
and the SI. Charles River (fig. I), which are major trib-
utaries to the Arkansas River between Pueblo Reser-
voir and the near-Avondale station, could affect the

6,OOO-ft3/s criterion, and hence, the operation of
Pueblo Reservoir, including the JUP. Therefore, Foun-
tain Creek and the St. Charles River were included in
the frequency analysis.

ROM discharges were used in the frequency
analysis for the PRJUP study because the primary
objective of the frequency analysis was to estimate
reservoir inflow volume during the study period, which
does not require a daily maximum instantaneous dis-
charge. The frequency analysis for Fountain Creek and
the SI. Charles River was used to derive 0.01 EP dis-
charges, not volumes; in this case, the use of ROM
discharges was considered satisfactory because (1) the
daily maximum instantaneous discharges for the histor-
ical record are not available, and (2) instantaneous
discharges in the two tributaries are attenuated consid-
erably by the larger Arkansas River channel. In actual
application of the study results (described in the
"Application of the Frequency-Analysis Results to
Estimate Evacuation Dates for the Joint-Use Pool"
section), there may be times when the instantaneous
discharge in the two tributaries exceeds 6,000 fills,
requiring a different operating procedure for Pueblo
Reservoir than that based on the 0.01 EP daily mean
discharges. However, the instantaneous peaks proba-
bly would be of short duration and would not substan-
tially affect application of the study results.

The ESP procedure, which enables estimation of
future discharge volumes (reservoir inflow) for a spec-

4 us. of Fraquency Analyala ond the Extended Streamflow Pradlctlon ProcedUl1l 10 Estlmala Evaeuallon Oal.a for Iho
Jolnt-Ua. Pool of Pueblo Reservoir, Colorado