Stream: Middle Creek ‎(Lower Segment)‎ Executive Summary

• Description: Stream: Middle Creek ‎(Lower Segment)‎ Executive Summary
• State: CO
• Water Division: 2
• Title: Stream: Middle Creek ‎(Lower Segment)‎ Executive Summary
• Water Supply Pro - Doc Type: Report/Study

Biological Data
The USFS, in September of 1997, collected stream cross section information, natural
environment data, and other data needed to quantify the instream flow needs for this reach of
Middle Creek. Middle Creek is classified as a medium stream (between 20 to 35 feet wide) and
fishery surveys indicate the stream environment of the Middle Creek supports rainbow trout
(Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis).
Field Survey Data
CDOW staff used the R2Cross methodology to quantify the amount of water required to preserve
the natural environment to a reasonable degree. The R2Cross method requires that stream
discharge and channel profile data be collected in a riffle stream habitat type. Riffles are most
easily visualized, as the stream habitat types that would dry up first should streamflow cease.
This type of hydraulic data collection consists of setting up a transect, surveying the stream
channel geometry, and measuring the stream discharge.
Biological Flow Recommendation
The CWCB staff relied upon the biological expertise of the cooperating agencies to interpret
output from the R2Cross data collected to develop the initial, biologic instream flow
recommendation. This initial recommendation is designed to address the unique biologic
requirements of each stream without regard to water availability. Three instream flow hydraulic
parameters, average depth, percent wetted perimeter, and average velocity are used to develop
biologic instream flow recommendations. The CDOW has determined that maintaining these
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 (Nehring
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 (Date), the
measured discharge at the time of the survey (Q), the accuracy range of the predicted flows
based on Maiming's Equation (240% and 40% of Q), the summer flow recommendation based
on meeting 3 of 3 hydraulic criteria and the winter flow recommendation based upon 2 of 3
hydraulic criteria. It is believed that recommendations that fall outside of the accuracy range of
the model, over 250% of the measured discharge or under 40% of the measured discharge may
not give an accurate estimate of the necessary instream flow required.
Table 1: Data
Party
Date
Q
250 % -40%
Summer (3/3)
Winter (2/3)
USFS
9/5/1997
2.8
7.1 — 1.1
1 5.1
2.8
The summer flow recommendation, which met 3 of 3 criteria and is within the accuracy range of
the R2CROSS model is 5.1 cfs. The winter flow amount, which meets 2 of 3 criteria, is 2.8 cfs.
Hydrologic Data and Analysis
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. This evaluation was done through a computation that is, in essence,
-3-