BOARD01130

• Board Meeting Date: 1/26/2000
• Description: ISF Section - Instream Flow Appropriations - Water Division 5
• Board Meetings - Doc Type: Memo

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three hydraulic parameters at adequate levels across riffle habitat -types, aquatic habitat in pools
and runs will also be maintained for most life stages of fish and aquatic invertebrates eNehring
1979; Espegren 1996).

For this segment of stream, one data set was collected with the results shown in Table 1 below.
Table 1 shows who collected the data (Party), the date the data was collected eDate), the
measured discharge at the time of the survey (Q), the accuracy range of predicted flows based on
Manning's Equation e240% and 40% of Q), the summer flow recommendation based upon
meeting 3 of 3 hydraulic criteria and the winter flow recommendation based upon 2 of 3
hydraulic criteria.

Table 1: Data

Party Date Q 250%-40% Summer (3/3) Winter (2/3)
BLM 7/9/98 4.73 11.8-1.9 5.7 1.8(1)

BLM = Bureau of Land Management (I) Predicted flow outside of (he accuracy range of Manning's Equation.
? = Criteria never met in R2CROSS Slaging Table.

Biologic Flow Recommendations
The BLM recommended a 5.75, 2.5, 1.6 and 1.0 cfs summer flow and a 1.3, 0.7 and 0.5 cfs
winter flow based on their July 9th, 1998, data collection effort and their water availability
analysis. Staff has reviewed the data collected by the BLM. The summer flow recommendation,
which meets 3 of 3 criteria and is within the accuracy range of the R2CROSS model, is 5.7 cfs.
The winter flow recommendation, which meets 2 of 3 criteria but falls outside of the accuracy of
the R2CROSS model, is 1.8 cfs. CWCB staff believes recommendations that fall outside of the
accuracy of the model, below 40% of the measured discharge, may underestimate the required
winter flow. To determine the winter flow recommendation, staff looked at valid winter flow
recommendations for the stream segment located above Trapper Creek (1.3 cfs) and considered
the lower accuracy limit of the R2CROSS model (1.9 cfs). After consulting with the Colorado
Division of Wildlife, staff believes 1.8 cfs will be sufficient to protect the natural environment to
a reasonable degree.

Hydrologic Data

After receiving the cooperating agencies' 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 was derived from data collected by the USGS
stream gage for East Middle Fork Parachute Creek near Rio Blanco (ID #09092850), which has a
drainage area of 22.1 square miles esee Gage Summary in Appendix C). The period of record for
this gage is 1976 to 1983, the period of record used by staff in their analysis was 1976-1983, or
seven years of record. The estimated drainage area of East Middle Fork Parachute Creek
upstream of Northwater and Trapper Creeks is approximately 20.6 square miles. The drainage
area upstream of Corral Gulch is 22.1 square miles. Tables 2 and 3 below display the estimated
flow of East Fork Parachute Creek at the confluence with Northwater and Trapper Creeks and
Corral Gulch, in terms of a percentage of exceedence. The orange shading highlights how often
the summer flow has been available and the blue shading highlights how often the winter flow
recommendations have been available.