BOARD00456

• Board Meeting Date: 1/25/2005
• Description: ISF Section - Instream Flow Appropriations - East Fork Escalante Creek
• Board Meetings - Doc Type: Memo

Table I: Data

Party Date Q 250% -40% Summer (3/3) Winter (2/3)
USFS 06/04/2004 4.45 11.1 - 1.8 4,9 1.2(1)
USFS 06/04/2004 4,31 10,8 - 1.7 2,8 1.1 (1)

BLM = Bureau of Land Management DOW = Division of Wildlife
(1) Predicted flow outside of the accuracy range of Malll1ing's Equation.

USFS = United States Forest Service
? = Criteria never met in R2CROSS Staging Table.

Biologic Flow Recommendation
The summer flow recommendations, which meet 3 of 3 criteria and are within the accuracy range
of the R2CROSS model, range from 4,9 cfs to 2,8 cfs (See Table I), The winter flow
recommendations, which meet 2 of 3 criteria but are outside the accuracy range of the R2CROSS
model, range from 1.2 to 1.1 cfs (See Table I), Averaging the two summer flow
recommendations within range results in a 3,9 cfs recommendation, Averaging the two winter
flow recommendations outside the range results in a 1.2 cfs recommendation, It is our belief that
recommendations that fall outside of the accuracy range of the model, over 250% of the
measured discharge or under 40% of the measured discharge may not give an accurate estimate
of the necessary in stream flow required, In these cases, CWCB staff relies upon the biological
expertise of the cooperating agencies to develop a biologic in stream flow recommendation, The
USFS has indicated that this is a high priority stream segment to them, however, because the
winter recommendation falls outside the accuracy range of the R2CROSS model, staff has
consulted with the recommending agency, Staff and the recommending agency believe the
winter flow recommendation of 1.2 cfs would be appropriate for the Board to file on (See Table
I),

Hydrologic Data

After receiving the cooperating agency's biologic recommendation, the CWCB staff conducted
an evaluation of the stream hydrology to determine if water was physically available for an
instream flow appropriation, The hydrograph below was derived from data collected by the
USGS stream gage for Escalante Creek near Delta, CO (ID #09151500), which has a drainage
area of 209 square miles (See Gage Summary in Appendix C), The total drainage area of this
segment of the East Fork Escalante Creek is approximately 25,7 square miles, The period of
record for this gage was 1976 to 1989, the period of record used by staff in their analysis was
1976 - 1989, or 14 years of record, Since this gage is heavily impacted by upstream diversions,
the estimated average flow was derived by adding average diversion records for the irrigation
season (March through October), Table 2 below displays the estimated average flow of East
Fork Escalante Creek.

Table 2: Estimated Stream Flow on East Escalante Creek:

Jan

Feb

Mar

Jun

Jul

Oct

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