WSP04023

• File Number: 8272.600.60
• Description: Colorado River Basin Salinity Control Program - Basin Member State Info - Utah
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 7/1/1990
• Title: Upper Colorado River Basin Rangeland Salinity Control Project
• Water Supply Pro - Doc Type: Report/Study

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CUrtis Formation
Entrada Sandstone

NONPOINT SALT SOURCES: Sources of salt within the watershed
occur in two main areas. The first is from the marine shales of
the Mancos Shale geologic formation. This formation contains
gypsum (calcium sulfate), lime (calcium carbonate) and minor
amounts of sodium chloride and sodium sulfate. These salts are
easily leached from the rock and are yielded both as solution
products and as inclusions in alluviated sedimentary materials.

The second source of salt is from alluvial terraces containing
predominantly calcium carbonate salts in the central portion of
the watershed. The calcium carbonate is also yielded both as
solution products and as inclusions in alluviated sedimentary
materials.

NONPOINT SEDIMENT SOURCES: Sediment is yielded from all areas of
the watershed at varying rates. The major source of sediment
occurs in the Mancos Shale badland area at the base of the Roan
and Book Cliffs. This is a naturally high sediment source area.
Stream channel bank erosion is another source of sediment.
Channel bank erosion may be partially controllable through
hydrologic rehabilitation of some adjacent watershed areas. It
should be noted that some channel bank erosion and instability
are to be expected in this region.

There are two major areas of sediment yield that are human-
impacted and can be rehabilitated to a near-natural background
erosion rate. The first area is designated as the pinion-
Juniper-Sagebrush Terrace and is located in the Mancos Pediment
area of Pinto Canyon and Nash Canyon Subwatersheds adjacent to
the Badland area. This area is composed of alluvial terraces
undergoing accelerated erosion and has high sediment yield rates.

The second area is designated as the Mancos Terrace and is
located in the Mancos Pediment area of Pinto Canyon and Nash
canyon Subwatersheds. This area is a low-lying former floodplain
terrace that has Mancos Shale exposed and eroding on the surface.
It is undergoing high to very high sediment yield rates and is a
significant source of sediment and salt.

These two areas represent the target area for project planning to
control nonpoint sediment and salt yield into the Colorado River.

GENERAL GEOMORPHOLOGY: The watershed is located in the Colorado
Plateau Physiographic Province and is contained within portion of
the following Physiographic Subdivisions: Book Cliffs-Roan
Plateau, Mancos Shale Lowland, Umcompaghre Extension and Salt
Anticline (Stokes
,1977). The dominant geomorphic features of the watershed are
formed as the result of geologic weathering. The dip of the rock

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