BOARD01592

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

Horsefly Creek at the confluence with the San Miguel River is approximately 110,0 square
miles, so higher flows would be expected at the mouth of the creek than at the gage location,
The period of record for this gage was 1942-1951, the period of record used by staff in their
analysis was 1942-1951, or 10 years of record, Table 2 below displays the stream flow of
Horsefly Creek, in terms of a percentage of exceedence,
Table 2: Estimated Stream Flow on Horsefly Creek
Exeeedenees Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nav Dee
10/0 3,8 7,6 30,6 1282,0 1661,7 354,5 9,8 35,8 18.4 13,9 14,9 2,7
50/0 3,8 7,6 30,6 754,5 644,8 55.4 4,6 3,8 1,3 7,7 9,6 2,7
10% 3,8 7,6 30,6 473,7 454,6 32,9 3.4 2,3 0,8 2,7 9,6 2,3
20% 1,1 1,5 22,9 343,8 223,1 19,9 2,0 0,8 0,0 1,9 1,9 1,5
80% 0,0 0.4 1,1 9,9 26,0 0.4 0,0 0,0 0,0 0,0 0,8 0.4
90% 0,0 0.4 0,8 5,7 13,8 0,0 0,0 0,0 0,0 0,0 0.4 0,0
95% 0,0 0,0 0,8 4,8 9,1 0,0 0,0 0,0 0,0 0,0 0,0 0,0
99% 0,0 0,0 0,8 2,7 1,7 0,0 0,0 0,0 0,0 0,0 0,0 0,0

Estimated Stream Flow on Horsefly Creek

20

5

15

lJ)
U 10

o

Jan Feb Mar Apr May Jun Jul Aug Sep Oet Nov Dee
Month

Table 2 shows that the summer flow recommendation of [3,0 cfs is available only from April I
to June 5, which corresponds with the snowmelt runoff period, Accordingly, the BLM
recommended that [3,0 cfs be appropriated during April I to June 5, and that no appropriation be
made for the remainder of the year because of limited water availability,

Precipitation Data
Staff reviewed local precipitation data sets from one site located around the Cottonwood Creek
Drainage (see Precipitation Data in Appendix C), Table 3 shows the water year and the percent
of average precipitation recorded for this site, It is staff's opinion that the ten years of stream-
flow data analyzed is representative of slightly below average water-years,

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