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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Unit 5 - MANCOS PEDIMENT - This unit is characterized by soil
developed on the Mancos Shale. There are areas of shale derived
soils and areas of sandstone or eolian derived soils within this
unit. The unit contains 59,116 acres. There are some areas
within this unit that need vegetative improvement. These areas
were not defined for this report: however, it is estimated that
approximately 25% of the area needs vegetative improvement. The
implementation of treatment measures to control accelerated
erosion would require hydrologic and vegetative measures on 40%
of the targeted acreage. The estimated Present condition and
FWOP condition annual sediment yield from this unit is 0.6 acre-
feet per square mile or 1.8 tons per acre (PSIAC sediment yield
classification 3 - moderately high). The estimated salt yield
rate is 3%. The estimated FWP sediment yield rate is 0.34 acre-
feet per square mile or 1 ton per acre (PSIAC sediment yield
classification 4 - moderate) for the 25% of the unit acreage in
need of treatment (of which only 40% needs to be treated to
achieve conservation goals). Treatment to improve rangeland
condition would result in the control of 3153 acre-feet or 9459
tons of sediment and the saving of 284 tons of salt. This area
is not recommended for project-level land treatment planning but
could be considered for treatment under annual planning.

unit 6 - SAGERS FLAT - This unit is a low sloping area adjacent
to the Badland unit. It is mostly contained within the Sagers
Wash Subwatershed and includes some western tributaries of Pinto
Wash Subwatershed. The unit contains approximately 15,018 acres
and it acts as a floodplain and a zone of deposition for the
Sagers Flat .Subwatershed. Field measurements of the channels in
the unit averaged about 10 feet deep and 20 feet wide. These
channels could contain up to 200 cubic feet per second (cfs)
without flooding. Hydrologic estimates of storm flows ranged
from a minimum of 388 cfs for a 2-year storm event in a tributary
of Sagers Wash to 3096 cfs for a 25-year storm event on the main
channel of Sagers Wash. Observation of this area in eroded
gullies resulted in an estimate of at least 3 feet of sediment
deposition in this floodplain. This unit plays an extremely
important role in the sediment delivery and hydrology of the
Sagers WashSubwatershed. It is a depositional zone for a
significant portion (estimated at 50%) of the sediment and salt
yielded from the Badland unit of the subwatershed.

This area is recommended for designation as a sensitive watershed
area where grazing should be minimized and vegetation should be
maximized. Aerial spraying to control noxious weeds is not
recommended if it will damage the existing floodplain vegetation.
The Present and FWOP condition annual sediment yield rate for the
area is estimated to be approximately 0.68 acre-feet per square
mile or 2 tons per acre (PSIAC sediment yield classification 3 -
moderately high). The estimated annual sediment yield from this
unit is 3006 acre-feet or 15,018 tons and 2253 tons of salt. The
estimated salt yield rate from this unit is 15%.

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