07/6/A-007 Supplemental Data

• Case Number: 07/6/A-007
• Stream Name: South Fork Big Creek
• Watershed: Upper North Platte
• Water Division: 6
• Water District: 47
• County: Jackson
• Instream Flow App - Doc Type: Supplemental Data

DRAFT INSTREAM FLOW RECOMMENDATION
Mr. Dan Merriman
Colorado Water Conservation Board
1313 Sherman Street, Room 721
Denver, Colorado 80203
Dear Mr. Merriman:
The Bureau of Land Management (BLM) is writing this letter to formally communicate its
instream flow recommendation for South Fork Big Creek, located in Water Division 6.
Location and Land Status. South Fork Big Creek is tributary to Big Creek north of the
Colorado - Wyoming border. This recommendation covers the stream reach beginning at the
confluence with Wheeler Creek downstream to the Colorado - Wyoming border. Approximately
98% of the 1.88 -mile reach is federally owned, while the remaining 2% is privately owned.
Biological Summary. South Fork Big Creek is a moderate gradient stream with large substrate
and a stable channel. Aquatic insects, water quality, pool habitat, and cover are excellent for
salmonids. Fishery surveys indicate self- sustaining populations of brown trout, long -nose dace,
and white sucker. The productivity of the fishery is very high. The riparian community is
vigorous and diverse, and provides substantial cover for the stream environment.
Is R2Cross Analysis. BLM's data analysis, coordinated with the Division of Wildlife, indicates
that the following flows are needed to protect the fishery and natural environment to a reasonable
degree.
10.2 cubic feet per second is recommended for the high temperature period from May 1 to
October 31. This recommendation is driven by the average velocity criteria and the
average depth criteria. It is important to provide adequate velocity and physical habitat
during this time for fish spawning and incubation of eggs. In addition, it is important to
provide adequate depth and velocity to maintain low water temperatures during late
summer and fall. Protecting flows during this time period is also important for
recharging the alluvial aquifer, which discharges water to the stream and maintains flow
levels during summer and fall.
8.2 cubic feet per second is recommended from November 1 through April 30. This
recommendation is driven by the average depth criteria. This flow rate will allow fish to
survive in pools, provide sufficient physical habitat in riffles between pools, and will
prevent the riparian environment from being seriously stressed.
Water Availability. BLM is not aware of any decreed water rights within this reach. However,
there are multiple diversions located upstream on South Fork Big Creek and on tributaries to this
creek, including the East Lynne Ditch, Independence Ditch, and Plainwell Ditch. It appears that