9342

• UCREFRP Catalog Number: 9342
• Author: Wynn, K. H., N. J. Bauch and N. E. Driver.
• Title: Gore Creek Watershed, Colorado--Assessment of Historical and Current Water Quantitiy, Water Quality, and Aquatic Ecology, 1968-98.
• USFW Year: 2001.
• USFW - Doc Type: Denver.
• Copyright Material: NO

Because of the direct relation between specific
conductance and dissolved-solids concentrations
in water, and because specific-conductance data
are more widely available for surface-water sites
in the Gore Creek watershed, specific conductance
will be discussed in this report.
Because of dilution, specific conductance
increases as streamflow decreases at site 29,
at the mouth of Gore Creek (fig. 12). Specific-
conductance values were highest during December-
March 1996-97. These specific-conductance values
coincided with low-flow conditions, when ground
water accounts for a larger portion of streamflow,
and discharges from tributary streams to dilute point
and nonpoint sources that enter Gore Creek are
reduced. The peak-flow months of May-July 1997
coincided with the lowest values for specific conduc-
tance (fig. 12), which can be attributed to large
volumes of relatively dilute snowmelt waters entering
Gore Creek. From October 1996 to September 1997,
mean daily specific conductance at site 29 ranged
from 94 MS/cm to 452 JlS/cm, with a median value
of 306 JlS/cm.

The spatial distribution of stream specific-
conductance values can be related to natural and human
sources of dissolved constituents in the watershed. The
highest specific-conductance values in tributary streams
to Gore Creek occurred at sites 38 and 49 on Black
Gore Creek and Mill Creek, respectively (fig. 13A and
13B). The higher values in these drainages can be partly
attributed to natural sources, such as the Pennsylvanian-
age sedimentary rocks, in these drainages. Human
activities in the Vail Mountain ski area also may
contribute to the higher specific-conductance values
in Mill Creek (fig. 13A). Application of traction sand
to the Interstate 70 roadway is also a contributing factor
for elevated specific conductance in Black Gore Creek.
Lorch (1998) estimated that the Colorado Department
of Transportation annually applies about 13,000 tons
of traction sanding material, including about 650 tons
of rock salt by weight, to the Interstate 70 roadway
between Vail Pass and the mouth of Black Gore Creek.
Lorch estimated that about 30 percent of the applied
traction sand is transported to Black Gore Creek annu-
ally; therefore, an estimated 195 tons of rock salt enters
Black Gore Creek, providing soluble material that can

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OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEPT
1996 1997

Figure 12. Mean daily streamflow and specific conductance at the mouth of Gore Creek.

26 Gore Creek Watershed, Colorado-Assessment of Historical and Current Water Quantity, Water Quality,
and Aquatic Ecology, 1968-98