WSP12030

• File Number: 8441.400
• Description: Colorado Big Thompson Project - Reports
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 4/1/1987
• Title: Joint-Use Reservoir and Green Mountain Exchange Projects - Final Report
• Water Supply Pro - Doc Type: Report/Study

I
I
,
,1 0
;1 C.:>
,
J ('"
.\ (.))
i
! tJl
, ~
i
I
1
I
,

To facilitate the computations involved in hydrologic and water rights data management, and

to perform the reservoir operation analyses, a monthly hydrologic simulation model was used. It

incorporated the Colorado water rights priority system and other legal and institutional

arrangements identified during the Study. The modeling area covered the Upper Colorado River

Basin above the Cameo gage near Palisade. This chapter describes the physical, legal and

operational considerations incorporated in the model. Reservoir .yields are described in the

following chapter and aitarnative yields and costs of the Green Mountain Exchange Project

components are described in Chapter 13.

3.1

HYDROLOGIC CHARACTERISTiCS

The Upper Colorado River watershed, which is the subject of this Study, extends from the

Continental Divide at an elevation in excess of 10,000 feet, to the Cameo gage near Palisade, 210

miles downstream, at an elevation of about 4,800 feet (see Figure 1.1). The drainage area above the

Cameo gage is approximately 8,000 square miles.

-

The major tributaries to the Colorado River in the study area are: the Fraser, Williams Fork,

Blue, Piney, Eagle, and Roaring Fork Rivers. Smaller streams which also contribute to the Colorado

River include Willow, Troublesome, Muddy, Rock, Divide, Elk, Rifle, Parachute, Roan, and Plateau

Creeks. Principal reservoirs located in the Upper Colorado River Watershed include: Grand Lake,

Shadow Mountain Lake, Lake Granby, Willow Creek Reservoir, and Green Mountain Reservoir, all

operated by the USBR as part of the CBT; Williams Fork and Dillon Reservoirs owned by the DWB;

Homestake Reservoir, jointly owned by the cities .of Colorado Springs and Aurora; and Ruedi

Reservoir operated by the USBR as part of the Fryingpan-Arkansas Project. .j

Precipitation varies dramatically within the study area. At the higher elevations, precipitation

exceeds 30 inches per year, whereas in Garfield County, 30 miles east of Grand Junction, Colorado,

annual precipitation is as low as 10 inches per year. Snowfall in the study area begins as early as

October a'nd ends as late as the end of April.

Average annual virgin flow of the Colorado River (based on 1951-1983 historical flows

adjusted for major diversions and reservoirs as described in Chapter 4) ranges trom about 0.5

million at at the headwaters near Hot Sulphur Springs to 3.1 million at at the Cameo gage. A wide

variation in total annual virgin flow is characteristic ot the river as illustrated by annuai extremes at

the Cameo gage of 1.7 million af in 1977 and 5.2 million af in 1983.

3-2

--