ISFAPPC02344

• Case Number: 02CW0273
• Stream Name: Mill Creek
• Watershed: San Miguel River
• Water Division: 4
• Water District: 60
• County: San Miguel
• Instream Flow App - Doc Type: Supplemental Data

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instream flow appropnatIOn. There are no currently operated or historically operated
streamflow gages for this reach. The closest gage CWCB staff found was the gage located on the
San Miguel River 1.6 miles west of Mill Creek drainage. The hydro graph was derived from data
collected by the USGS stream gage for the San Miguel River near Telluride, CO (ill
#09171200), which has a drainage area of 42.8 square miles. The drainage area of Mill Creek is
approximately 5.3 square miles. Staff used a basin apportionment method to estimate stream
flows for Mill Creek (See Gage Summary in Appendix C). The period of record for this gage
was 1959 to 1965, the period of record used by staff in their analysis was 1959 - 1965, or six
years of record. Table 2 below displays the estimated flow of Mill Creek above the San Miguel
River, in terms of a percentage of exceedence.

Estimated Mill Creek Stream Flow
Exceedences
1%
5%
10%
20%
50%
80%
90%
95%
99%

35
30
25
20
J1
u 15
10
5
o

Januarv Februarv March April May June July August September October November December
2.27 2.52 6.37 13.14 50.94 58.97 52.48 25.88 11.66 6.08 4.20 2.90
2.14 2.39 3.86 11.33 43.94 52.24 45.12 15.20 9.19 5.00 3.65 2.52
2.01 2,39 2.95 9.82 30.06 45.32 33.84 11.86 8.18 4.78 3.52 2.39
2.01 2,27 2.52 7.68 23.26 39.03 25.33 9.57 7.05 4.15 3.27 2,27
1.89 1,89 2.01 4.41 14.98 29.21 12.21 6.42 4.66 3.40 2.77 2.14
1.76 1.76 1.76 2.77 8.81 16.62 6.92 4.91 3.40 2.90 2.52 2,01
1.64 1.76 1.76 2.01 5.49 14.60 5.61 4.15 3.27 2.77 2.39 2.01
1,64 1.76 1.76 2,01 4.57 12.59 5.07 3.65 3.15 2.77 2.39 1.64
1,64 1.76 1.51 1.99 3.65 10.15 4.12 3.40 3.02 2.64 2.27 1.64

Mill Creek Estimated Stream Flow

<t.r1,.- ~ ~~ ~~ ~)- </&1,.- t/~ ~&Q O'~~ 00;- 1,.-0~ O~O

Month

Table 2 shows that the summer recommendation of 6.7 cfs is available at least 50% of the time
from May 1st - July 14th and the winter recommendation of 2.4 cfs is available July 15th -
November 30th. The winter recommendation was further reduced to 1.9 cfs from December 1 st -
May 14th due to water availability concerns.

Precipitation Data
Staff reviewed local precipitation data sets from 2 different sites located around Mill Creek
Drainage (see Precipitation Data in Appendix C). These sites include Telluride (1900-1999) and
Ames (1914-1986). Table 3 shows the water year and the percent of average precipitation
recorded at each site.