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• Board Meeting Date: 11/18/2007
• Description: ISF Section - Uncontested 2007 Instream Flow Appropriations
• Board Meetings - Doc Type: Memo

For this segment of stream, 2 data sets were collected with the results shown in Table 1 below.
Table 1 shows who collected the data (Party), the date the data was collected (Date), the
measured discharge at the time of the survey (Q), the accuracy range of the predicted flows
based on Manning's Equation (240% and 40% of Q), the summer flow recommendation based
on meeting 3 of 3 hydraulic criteria and the winter flow recommendation based upon 2 of 3
hydraulic criteria.
Table 1: Data
Part Date Q 250%-40% Summer (3/3) Winter (2/3)
BLM 10/7/2005 3.88 9.7 1.6 4.2 NA
BLM 8/19/2004 4.89 12.2 2.0 8.4 NA
BLl\I = Bm'eau of Land Management DOW = Di~~ision of Wildlife
Biolo:;ic Flow Recommendation
The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range
of the R2CROSS model is 6.25 cfs (See Table 1). This recommendation was derived by
averaging the results of the two data sets. 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 instream flow required.
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 Cochetopa Creek Below Rock Creek Near Parlin, CO (ID #09118450),
which has a drainage area of 334 square miles (See Gage Summary in Appendix C). The total
drainage area of the Pauline Creek drainage is approximately 42 square miles. The period of
record for this gage was 1981-2005, the period of record used by staff in their analysis was 1981-
2005, or 25 years of record. To provide for a more accurate estimate of the stream flows on
Pauline Creek, the mean monthly consumptive use associated with upstream diversions was
added to the mean monthly stream flows. The consumptive use was assumed to be 50% of the
diversion amount. In addition, a senior ti-ansbasin diversion (Cochetopa Meadows Ditch) is
located above the proposed instream flow water right. The mean monthly diversion amounts
were subtracted from the estimated flows on Pauline Creek.
Table 2 and Figure 1 show that the summer flow recommendation of 6.25 cfs (2.75 cfs
enlargement) is available on average for the time period of May 1 through June 30. The summer
flow recommendation was reduced to 5 cfs (2.0 cfs enlargement) for the time periods of April 1
to April 30 and July 1 to August 31, based on limited water availability. The summer flow
recommendation was reduced further to 4.5 cfs (1.0 cfs enlargement) for the time period of
September 1 to September 30, based on limited water availability.
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