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

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I. Sum the O.oJ EP discharges for Fountain Creek
and the 51. Charles River.

2. If the sum from step I is equal to or greater than
6,000 ft3/s, then all the discharge for the near-
Pueblo station (reservoir inflow) is stored in the
JUP. Discharge for the near-Avondale station
is equal to the sum from step I.

3. If the sum from step I is less than 6,000 ~/s, then
any of the discharge for the near-Pueblo station
that will not cause the 6,ooo-ftl/s criterion to be
exceeded is assumed to be reservoir outflow
and is added to the sum from step I; the new
sum is the discharge for the near-Avondale sta-
tion. Any inflow discharge for the near-Pueblo
station that would cause the 6,OOO-ff/s crite-
rion to be exceeded is stored in the JUP.

4. If the new sum from step 3 includes all the inflow
discharge for the near-Pueblo station and the
sum is less than 6,000 ftl/s, then a release can
be made from the JUP if some inflow discharge
was stored in the JUP on a previous day, to
increase the discharge for the near-Avondale
station to 6,000 ff/s.

5. The estimated evacuation date for the JUP is the
day prior to the date when continuous storage
is required in the JUP.

The computation using the O.oJ EP discharges
for the near-Pueblo station (table 7) provides an esti-
mate of the date by which the JUP should be evacuated
for a reservoir inflow volume equal to the sum of the
0.01 EP discharges for the near Pueblo station (table 4).
This inflow volume is about I 68,800-acre-ft (note:
acre-feet = cubic feet per second x 1.9835); the esti-
mated evacuation date for the JUP for that inflow vol-
ume is April 23 (table 7).
To estimate the evacuation dates for other
April IS-May 14 inflow volumes, estimated daily mean
discharges for several other EPs were derived from the
frequency analysis for the near-Pueblo station. To
accurately evaluate how the estimated evacuation date
varies for other inflow volumes, all variables, except
the variable affecting inflow volume, should be the
same as in the estimation listed in table 7. Therefore,
the om EP discharges for Fountain Creek: and for the
SI. Charles River (tables 5 and 6) were used to estimate
the evacuation date for other inflow volumes. Prima-
rily for purposes of comparison to the data to estimate
the evacuation date using the om EP daily inflow dis-
charges (table 7), data to estimate the evacuation date
using the 0.50 EP daily inflow discharges are listed in

table 8. The estimated evacuation date for the JVP
using the 0.50 EP daily inflow discharges is May 5.
Data for estimating the JUP evacuation date for daily
inflow discharges other than the om and 0.50 EP daily
inflow discharges (tables 7 and 8) are not presented
herein; however, results of all the evacuation date esti-
mates are listed in table 9. The assumptions and com-
putations for the additional evacuation-date esti-
mations were the same as those described in the previ-
ous paragraphs in this section. Results from estimating
the JUP evacuation date indicated a relation between
the estimated April15-May 14 inflow volume (the sum
of the daily inflow discharges derived from the fre-
quency analysis) and the JUP evacuation date; the re]a-
tion is shown in figure 17.

The relation shown in figure 17 may be subject to
some error because of the method by which the inflow
volumes were derived-by summing the daily inflow
discharges for the various EPs (table 9). The inflow
volumes derived by this method are different from the
inflow volumes derived by frequency analysis of
recorded April IS-May 14 inflow volumes (table 9). It
is not likely that all the April] 5-May ] 4 daily inflow
discharges in a given year would be equal to the daily
discharges at a specific EP, which was assumed in esti-
mating the evacuation dates (tables 7-9). Ana]ysis of
ROM discharges for the ten years of largest April-May
discharge volume did not indicate a dominant correla-
tion between rank: of a discharge volume and the num-
ber of days for which the daily discharge rank was
equal to or greater than the volume rank (tables 2-4).

To evaluate the possible error in the inflow vol-
ume/evacuation date relation (fig. 17), the diversion-
adjusted ROM discharges for April IS-May 14 for all
years of record (including the extended record for
1976-90) were routed through Pueblo Reservoir. The
routing technique was identical to that previously
described and shown in tables 7 and 8, except that the
ROM discharges for the near-Pueblo station were used
for reservoir inflow. The 0.0 I EP discharges for Foun-
tain Creek: and the 51. Charles River were used. A
cumulative frequency distribution of the April 15-
May 14 inflow volumes derived from the April 15-
May 14 ROM inflow discharges is shown in figure] 8.
Results of routing the diversion-adjusted RDM
discharges through Pueblo Reservoir to estimate evac-
uation dates for the corresponding inflow volumes
(fig. 18) are shown in figure ]9. The estimated evacu-
ation dates are clustered around only a few dates
(figs. ]7 and ]9) because of peaks in the 0.0] EP dis-
charges for Fountain Creek: and the St. Charles River
(fig. 20). Because the relation of inflow volume to
evacuation date when the ROM inflow discharges were
routed through Pueblo Reservoir (fig. ] 9) is not sub-

34 U.. 01 Frequeney Analysts end the Extended Stresmflow Predletlon Procedure to Eatlmsta Evacuation Dstes lor tha
Jotnt-Usa Pool 01 Pueblo Reaarvolr, Colonldo