ISFAPPC01553 ‎(2)‎

• Case Number: 07CW0062
• Stream Name: Alder Creek
• Water Division: 3
• Water District: 25
• County: Saguache
• Instream Flow App - Doc Type: Supplemental Data

0 0 V
Biologic Flow Recommendation
The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range
of the R2CROSS model is Llcfs (See Table 1). The winter flow recommendation, which meets
2 of 3 criteria and is within the accuracy range of the R2CROSS model is 0.5 cis (See Table 1).
These recommendations were derived by average 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 406/o 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 San Luis Creek Near Poncha Pass, CO (ID #08224110), which has a
drainage area of approximately 6.6 square miles (See Gage Summary in Appendix Q. The total
drainage area of the Alder Creek Drainage is approximately 6.0 square miles. The period of
record for this gage was 1979-1985, the period of record used by staff in their analysis was 1979-
1985, or 8 years of record. Table 2 below displays the estimated stream flow of Alder Creek, in
terms of a percentage of exceedence.
Table 2 and Figure 1 show that the summer flow recommendation of 1.1 cfs is available at least
50% of the time during the period of April 15th to Jun 14th. Table 2 also shows that the winter
flow recommendation of 0.5 cfs is available at least 50% of the time from June 15"' to April 14th
Table 2: Estimated flow on Alder Creek (cfs)
Exceedence Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1% 0.8 1.0 1.3 3.7 6.4 4.1 1.8 2.5 1.3 1.3 2.0 1.6
5% 0.8 0.9 1.2 2.7 5.2 2.9 1.4 1.2 0.9 1.1 1.4 1.5
10% 0.8 0.9 1.2 2.3 4.6 2.6 1.2 0.9 0.8 1.0 1.3 1.4
20% 0.8 0.8 1.0 1.7 4.0 2.2 1.1 0.8 0.6 0.9 1.2 1.0
50% 0.6 0.7 0.8 1.3 2.0 1.2 0.7 0.6 0.5 0.6 0.8 0.7
80% 0.4 0.5 0.7 0.8 1.2 0.5 0.3 0.3 0.3 0.4 0.6 0.6
90% 0.3 0.4 0.6 0.7 0.8 0.4 0.2 0.3 0.2 0.3 0.5 0.5
95% 0.3 0.4 0.6 0.6 0.7 0.3 0.2 0.2 0.2 0.2 0.5 0.4
99% 0.3 0.3 0.5 0.5 0.6 0.3 0.1 0.1 0.1 0.2 0.4 0.4
-4-