WSP10444

• File Number: 8441.400
• Description: Colorado Big Thompson Project - Reports
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 8/1/1986
• Author: Colo. Water Resource
• Title: Summary Report - Preliminary Hydrologic Analysis
• Water Supply Pro - Doc Type: Report/Study

r
l~
,,(;11
',"""
...,.,
I:w

'.<"1

I
I

',"~oj
,

,,:

I

L

6!

I

I,

. :~

L

:'t

'I'
~. -~

.' ;.

'/'
t\
, "~
{ ;:
?';

'y

~:- ;.

~: :
:,
J
'.

. :1'

~::"{
~,(
I
.;:},
>.i

'(

i.

simulated results are in good agreement with recOrded data. Some
discrepancies, in the Green Mountain Reservoir contents during April
through June. a.re due to difficulties in duplicating' historical
power releas,e scheduleS whioh werehig'hly variable during this
period.

5.:2 PROJECT RESERVoIR YIEJ,DS

The hydrolog'ic simulation l\)odel was applied to estimate storable
water ,ateaohproposed reservoir site under the three developmemt
so.enarios discussed in section 3.0. Under each development
scenario, two different conditions for the. operation of Green
Mountain Reservoir were aSs,umed. One condition" referred t.o as
"wi thoutPumpback'l , assumes that Green Mountain ReServoir will
co!}tinue to operate in accordance with $enate Document 80. The
other condition aSsumes that water will be pumped from Green
Mountain Reservoir to Dillon Reservoir. This second condition
reflects one . of the. alternatives envisioned under the Green
Mountain Reservoir Exchange concept. Two alternative' pumpback
capacities were studied. The "154,000 Pumpback", alternative
assumes that the entire storage of Green Mountain neservoir,
(approximately 154,000 af) be made available for pumpback to Dillon
Reservoir except for the required 60 cfs minimum flow requirement.
The. other alternative analyzed in. this study assumes that the
active storage of 52,000 at' be kept in Green Mountain Reservoir to
be used to satisfy CBT out-of-priority diversions, while the
remaining power pool l;>e used to supply water to Dillon ReserVoir.
This alternative is referred to as "100,000 PUmpback".

Subsequl;!nt to the hydrOlogic . analysis which provided estimates of,
storable flows , the. reservoir operation analysis was performed to
estimate the firm annual yield of each reservoir. The firm annual
yield is defined .for the purpoSe of this study as the constant
vOlUme of water tha.t can be supplied every year without any
shortage during th.e study period of 1951 through 1.983. It was

,5-8