WSP07477

• File Number: 8407
• Description: Platte River Basin - River Basin General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 7/14/1997
• Author: USGS
• Title: Hydrologic and Water-Quality Data - Guanella Pass Area - Colorado - Water Year 1995
• Water Supply Pro - Doc Type: Report/Study

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The authors are grateful to Historic Georgetown, Inc.,
Public Service Company of Colorado. William and
Julia Holmes, Clear Creek and Park Counties, and the
U.S. Department of Agriculture, Forest Service, for
access to propertY.

DESCRIPTION OF STUDY AREA

The study area encompasses the basins of South
Clear Creek, Geneva Creek, and part of West Chicago
Creek (fig. I), which are all tributary watersheds to the
South Platte River. The West Chicago Creek site is
adjacent to the South Clear Creek watershed and was
added to provide an additional reference (natural) site.
The Continental Divide forms the headwaters along
the western boundary of the study area. The tributary
headwaters on the eastern side of the study area are
located in the Mt. Evans/Mt. Bierstadt area. The
Guanella Pass road parallels South Clear Creek from
the northern terminus at Georgetown to the top of
Guanella Pass at 11,669 ft. South of the pass, the road
follows Duck Creek to the confluence with Geneva
Creek and then follows Geneva Creek to the southern
end of the road at Grant. The road has been designated
as a scenic byway and is called Forest Highway
(FH) 80. The northern 13.1 mi. alternatively known
as Clear Creek County Road 381, is located in Clear
Creek County. The southern 10.4 mi, alternatively
known as Park County Road 62, is located in Park
County. The route is maintained year round by the
respective counties. Salt is applied with traction
materials to parts of the road in Clear Creek County
during winter. Magnesium chloride has been applied
to parts of the road in Clear Creek County to control
dust (Jim Cannedy, Clear Creek County, oral
commun., 1997). The Guanella Pass road is 23.5 mi
long. of which 12.1 mi is dirt or gravel and 11.4 mi has
an asphalt surface (Federal Highway Administration,
1993).
The area is sparsely populated. Some residences
are at Duck Lake and along Duck, Geneva, and
lower South Clear Creeks. The primary land use is
recreational. Livestock grazing is a limited land
use in the Geneva, Scott Gomer, and Duck Creek
drainages. The former Geneva Basin Ski Area is
located south of Guanella Pass and Duck Lake. The
Mt. Evans Wilderness Area encompasses much of
the eastern one-half of the study area and is closed to
motor vehicles. The Vidler Tunnel diverts water from
upper Peru Creek across the Continental Divide into

the Leavenworth Creek Basin. An aqueduct diverts
water from Leavenworth Creek on a seasonal basis for
maintaining water levels in Green Lake. Some of the
natural lakes have been modified for storage by the
construction of small dams. The Public Service
Company of Colorado operates two reservoirs in the
South Clear Creek Basin for hydroelectric power
generation. Duck Lake also provides a minor amount
of water storage.
Vegetation includes conifer and aspen forest at
lower elevations and alpine tundra above timberline
near 11,500 ft. Annual precipitation in the study area
ranges from 12 to 16 in. near Georgetown and Grant,
to 40 to 50 in. on Mt. Evans and the Continental Divide
(Colorado Climate Center, 1984). Annual stream-
flows are characterized by peak flows in June resulting
from snowmelt and by low flows during winter. Short
afternoon thunderstorms occur during summer.
Precambrian granite, gneiss, and schist
compose the bedrock in the study area. Intrusive
rocks of Tertiary age underlie the headwaters of
Geneva and Leavenworth Creeks. Glaciers deposited
drift in the valleys of Duck, Geneva, and South Clear
Creeks (Tweto, 1979) and created many of the
natural lakes in the area.
Ore deposits containing the minerals galena.
sphalerite, pyrite, chalcopyrite. and tetrahedrite-
tennantite were mined near the headwaters of
Geneva and Leavenworth Creeks. These areas were
known as the Geneva Creek and Argentine Districts,
respectively (Davis and Streufert, 1990). Naturally
occurring pyritic components of the intrusive rocks
and mineral deposits become oxidized and produce
acidic ground water and surface water in the upper
basins of Geneva Creek (Bassett and others. 1992)
and Leavenworth Creek.

TYPES OF HYDROLOGIC AND
WATER-QUALITY DATA

Several types of data and samples were
collected during water year 1995. Daily suspended-
sediment concentration and load data collected at five
sites were not available for this report. The types of
data collected at each site are listed in table I. The
types of data presented in this report are:

1. Continuous streamflow: Daily mean values (ft3/s).
2. Continuous water-quality monitoring data: Mean
daily specific conductance (I!S/cm), and maximum
and minimum daily water temperature ("C).

DESCRIPTION OF STUDY AREA 3