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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purpose was to derive flow data at the lower station on Black Gore Creek for
1970 and 1972.

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It appears that Gore Creek is a losing stream for most of the distance

between the confluence of Black Gore Creek and the Eagle River. The losses

became evident when the sum of the gages on Booth, Pitkin, Bighorn, Upper Gore,

and Black Gore Creeks was compared with the Vail gage record. A review of the

IS-minute Geologic Quadrangle of the Minturn area revealed the existence of

significant alluvial deposits in Gore Creek. The deposits are of considerable

depth and cover the Gore Valley floor from near the confluence of Black Gore

Creek to about one mile upstream of the confluence with the Eagle River. It

appears that a portion of the Gore Creek flow enters the alluvium near the

upper end of the valley and travels through it to a point near Gore Creek' s

confluence with the Eagle River. At this point bedrock is exposed which brings

the underground flow to the surface.

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Stream loss to the Gore Creek alluvium was concluded to be significant

above Point A. Stream loss was then assumed to occur within each study reach

below Point A (see Figure 1). Obtaining more accurate values for stream loss

in the study reaches would require an extensive streamflow measurement program

over a range of flow conditions. Such an investigation was beyond the scope of

this study. The estimates presented are intended to reflect a worst-case

scenario in an effort to provide conservative estimates of potential impact.

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Losses were calculated monthly on a per mile basis from the data above

Point A, then applied to each study reach length located within the Gore Creek

alluvium. Stream loss was found by detet1ll.inin~ the difference between upstream

tributary inflow and the gage record, in cubic feet per second (cfs). Losses

were apportioned among the stream reaches by summing the stream length on the

valley floor between the upper and lower gages, then dividing the total loss by

the total stream-channel length (5.6 miles). The resulting loss-per-mile

values were applied to individual study reaches to obtain estimates of monthly

stream loss. These calculations were made on a monthly basis for the entire

study period. Results are given in columns 14, 15 and 16 in Appendix A.

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