WSP06951

• File Number: 8273.300
• Description: Colorado River Basin Salinity Control - Federal Agencies - USGS
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1985
• Author: USGS
• Title: Ground-Water Contribution to the Salinity of the Upper Colorado River Basin
• Water Supply Pro - Doc Type: Report/Study

Roaring Fork River

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The Roaring Fork River subbasin includes the drainage area of the Roaring
Fork River and tributaries upstream from the confluence with the Colorado
River. Igneous rocks underlie most of the headwaters of the main stem of the
Roaring Fork River in the southern part of the subbasin. Pennsylvanian and
Permian sandstones and localized areas of igneous rock and unconsolidated
deposits crop out in the headwaters region of most of the major tributaries
of the Roaring Fork River. At lower elevations the Upper Cretaceous Mancos
Shale crops out along the southwestern side of the Roaring Fork River, and
Lower Triassic, Pennsylvanian, and Permian sandstones, conglomerate, and
mar1stones together with a mixture of basalt and unconsolidated deposits occur
along the northeastern side of the Roaring Fork River.

The Fryingpan River is a major tributary to the Roaring Fork River.
Headwaters of the Roaring Fork and Fryingpan Rivers discharge water having a
mean annual dissolved-solids concentration of generally less than 100 mg/L.
At its mouth the Roaring Fork River has a mean annual dissolved-solids
concentration of about 250 mg/L. The high mountains that form the headwaters
region of the Roaring Fork River are the source of very large quantities of
water. The' mean annual discharge of the Roaring Fork River near its mouth is
about 860,000 acre-ft (600 acre-ft/mi2).

Thirteen sampling sites were selected in this subbasin (figs. 3 and 7;
table 2). The dissolved-solids concentration in the Roaring Fork River
upstream from Aspen, Colo. (site 13), of 62 mg/L is the result of the
predominance of insoluble igneous rocks upstream from this site. The,'
estimated base-flow salt load was 1,400 ton/yr and a discharge of 23 ft3/s.
The dissolved-solids concentration of Castle Creek (site 14) was about
350 mg/L and Maroon Creek (site 15) was about 370 mg/L. The Maroon Formation,
which consists of Pennsylvanian and Permian sandstones, conglomerate, and
siltstone, is drained by Maroon and Castle Creeks and may contribute to the
higher salinity concentrations at these sites. The Maroon Formation of,
Pennsylvanian and Permian age intertongues with the underlying Eagle Valley
Evaporite of Pennsylvanian and Permian age. The Aspen Mountain Ski Area near
Aspen, Colo., which is drained by these streams, also'may contribute to the
higher salinity concentrations.

Dissolved-solids concentration in the Roaring Fork River downstream from
Woody Creek (site 16) was 316 mg/L. At this site, the estimated base-flow
salt load has increased to 32,700 ton/yr with a base-flow discharge of
105 ft3/s. This is primarily a result of the effects of Castle and Maroon
Creeks that contribute a combined base-flow salt load of about 23,100 ton/yr
and a combined base-flow discharge of about 65 ft3/s. The dissolved-solids
concentration in Snowmass Creek (site 19) waS about 440 mg/L. Outcrops of the
Mancos Shale that underlie the area may be responsible for the larger salinity
concentrations in Snowmass Creek. The base flow of the creek was 26 ft3/s and
carried a salt load of 11,300 ton/yr. The dissolved-solids concentration
(about 320 mg/L) in the Roaring Fork River between Woody Creek and the
confluence with the Fryingpan River (site 20) is 'almost the same as the
concentration (316 mg/L) above Woody Creek (site 16).

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