WSP11259

• File Number: 8441
• Description: Colorado - Big Thompson - Green Mountain
• State: CO
• Basin: South Platte
• Date: 3/12/1985
• Author: CRWCD by West. Eng.
• Title: Green Mountain Reservoir Water Sales Impact on Flows in Gore Creek
• Water Supply Pro - Doc Type: Publication

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WATER SUPPLY ANALYSIS

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The study was conducted by simulating future VVCWD water use patterns with

streamflow conditions representative of "wet", "normal". and "dry" water years.

This analysis concentrates on that portion of Gore Creek between its

confluences with Black Gore Creek and Red Sandstone Creek. The study

concentrates on this section of Gore Creek because: (1) this se~ent includes

the VVWCD snowmaking diversion, and (2) municipal diversions are physically

removed from the stream channel between the various raw-water intakes snd the

wastewater treatment plant at Red Sandstone Creek (see Figure 1). The

methodology used in completing the study required: (1) defining all possible

VVCWD diversion locations and subdividing them into groups corresponding to

stream sub-sections or reaches, (2) relating. future demand, return flow, stream

loss, and tributary inflow to each reach, and (3) combining all the above data

into a simple streamflow model to produce an estimate of streamflow depletion.

Water use data and diversion locations used in this analysis were obtained

primarily from VVCWD's application for water service from Green Mountain

Reservoir. Other data was obtained from Tipton and Kalmbach, Inc. of Denver,

consultants to the VVCWD.

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Gore Creek Hydrology

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Streamflow on Gore Creek exhibits characteristics similar to other high

elevation watershed.s in the Rocky Mountain Region. The flows are primarily

derived from snowmelt runoff which usually peaks in Mayor June. Historically,

the U. S. Geological Survev (USGS) has maintained several streamflow gaging

stations within the Gore Creek drainage bssin. Table 1 shows the statio.ns

which existed during the three study years (1970,1972,1977). The data from

chese stations was used to define flow conditions on Gore Creek.

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Five critical points on Gore Creek were selected for streamflow analysis.

The positions of the points correspond to a former gaging station location,

points just upstream of significant tributary stream confluences, and a poirit

at the lower end of the critical segment. Figure 1 illustrates these five

points. Point A corresponds to the location of the USGS station on Gore Creek

at Vail (No. 09066250). Table 1 shows that data for this station is available

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