BOARD00154 ‎(2)‎

• Board Meeting Date: 3/13/2007
• Description: ISF Section - Notice of 2008 Instream Flow Recommendations and Summary of ISF Workshop
• Board Meetings - Doc Type: Memo

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The information contained in this report and the associated appendices serves as the basis
for the instream flow recommendation to be considered by the Colorado Water
Conservation Board (Board). It is the professional opinion of the staff of both Trout
Unlimited (TU) and the Colorado Division of Wildlife (CDOW) that the information
described in these documents is sufficient for the Board's staff to begin the investigations
required to establish an instream flow appropriation under Rule 5 i of the Instream Flow
Rules.

Arapaho Creek originates at the outflow of Caribou Lake, which sits at an elevation of
11,100 feet in a basin between North Arapaho Peak and Satana Peak. It flows generally
northwest through U.S. Forest Service dropping nearly 3,000 feet to its confluence with
Buchanan Creek at 8,400 feet over a distance of approximately 7.8 miles. From there the
stream continues northwest through Monarch Lake and on to Lake Granby. The
proposed instream flow reach is between Caribou Lake and Arapaho's confluence with
Buchanan Creek. It is entirely on Forest Service Land.

Table 1: Ara aho Creek Land Status Review
Total Length
miles

Caribou Lake

Lower Terminus
Confluence with
Buchanan Creek

Land Ownershi
% Private %Public

U er Terminus

7.8

0% 100%

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Instream Flow Recommendations
TU and CDOW are recommending instream flow appropriations of 4.5 cfs during the
summer (4/15 - 8/31) and 1.9 cfs during the early winter (9/1 - 4/14). These
recommendations are based on the physical and biological data collected to date and do
not incorporate any water availability constraints. An R2CROSS analysis of cross-
sectional data collected on 9/17/06 was relied on to develop these recommendations
(Table 2). Three instream flow hydraulic parameters, average depth, percent wetted
perimeter, and average veloCity, are used to develop biologic instream flow
recommendations. The CDOW has determined that by maintaining these three hydraulic
parameters at adequate levels across rime habitat types, aquatic habitat in pools and runs
will also be maintained for most life stages of fish and aquatic invertebrates (Nehring
1979; Espegren 1996). The modeling results from this effort were within the confidence
interval produced by the R2CROSS model (Appendix B).

Table 2: Ara aho Creek R2Cross Summa
Confidence Interval cfs
Par Date Q cfs 250%-40%
TU 9/17/2006 4.41 11.0 - 1.8 4.47 1.92
. Recommendations based on meeting specified number of hydrologic criteria (average depth. percent wetted
perimeter and average velocity).

e

Biological Data
The study reach was fished with fly rods for approximately one hour on July 31, 2006.
Over 40 fish were caught. All the fish were brook trout ranging in size from 4" to 9".
Additional, smaller brook trout (fry) were observed in shallow waters near the stream
edge.