21

• Board Meeting Date: 7/11/2007
• Description: ISF Section - Pine River Water Acquisition
• Board Meetings - Doc Type: Memo

which meet 3 of3 criteria and are within the accuracy range of the R2CROSS model, range from 260 cfs to
186 cfs. The winter flow recommendations, which meet 2 of 3 criteria and were within the accuracy range
of the R2CROSS model, range from 161 cfs to 115 cfs (see Table 2 below).

T hi 2 F t B 'd S't

a e 00 n 1ge 1 e:
Date XS# Q QRanQc 3/3 2/3
4/8/04 I 124.9 312-50 222 ---
4/8/04 2 131.3 336-54 200 115
4/8/04 " 122.6 306-49 186 ---
.)
4/8/04 4 136.7 340-54 260 161
A vera2e 217 138

Averaging the four summer flow recommendations within range, results in a 217 cfs recommendation.
Averaging the two winter flow recommendations within range, results in a 138 cfs recommendation.

ISF Recommendation to Presel'Ve the Natural Environment to a Reasonable Deeree
To summarize the data listed above, the CDOW collected stream cross section data at 11 different locations
within the proposed instream flow reach of the Pine River. The average width of the stream channel
increased from approximately 70 feet to approximately 110 feet from the upper third of the stream reach,
CWR data collection site, to the lower third of the proposed stream reach, FB data collection site. The
CD OW believes the two different data collection sites represent the different and distinct types of natural
environments found within this reach of the Pine River (i.e. narrow confined reach to wide unconfined
reach). The summer flow recommendations, which meet 3 of 3 criteria and were within the accuracy range
of the R2CROSS model, range from 260 cfs to 72 cfs. The winter flow recommendations, which meet 2 of
3 criteria and were within the accuracy range of the R2CROSS model, range from 161 cfs to 30 cfs.
Averaging the 11 summer flow recommendations within range, results in a 136 cfs recommendation.
Averaging the seven winter flow recommendations within range, results in a 75 cfs recommendation.

ISF Recommendations to Improve the Natural Envit'onment.
The CDOW used the Tennant Method (a.k.a. Montana Method) in conjunction with the stream cross section
data collected in April and July of 2004, to determine the proposed flows for improving the natural
environment. CDOW analyzed the data recorded by the stream gage "Los Pinos River near Bayfield - ID
Number 09353500", period of record of 1927 - 1986, to determine the average annual flow (see attached
gage and cross section data).

Based on this analysis the CD OW recommends:

. Flows between 360 - 217 cubic feet per second are recommended for the May 1 through May 31
time period. The CD OW believes flow amounts in this range would improve the natural
environment to a reasonable degree by providing optimum to outstanding habitat;

. Flows up to 720 cubic feet per second are recommended for June 1 through June 14 time period.
The CDOW believes flows up to 720 cfs would improve the natural environment to a reasonable
degree by providing flushing flows;

. Flows between 360 - 217 cubic feet per second are recommended for Junel5 through October 14
time period. The CD OW believes flow amounts in this range would improve the natural
environment to a reasonable degree by providing optimum to outstanding habitat;

. Flows between 140 - 75 cubic feet per second are recommended for October 15 through April 30
time period. The CD OW believes flow amounts in this range would improve the natural
environment to a reasonable degree by providing outstanding habitat.