9344

• UCREFRP Catalog Number: 9344
• Author: Camp Dresser & McKee Inc.
• Title: Replacement of the Plateau Creek Pipeline.
• USFW Year: 1996.
• USFW - Doc Type: Denver.
• Copyright Material: NO

A
annual make-u flows exceeded 1500 ac-ft/ in 5 out of the 19 ears 26 ercent of the time .Thus,
P Yr Y ( P )
calculation of actual make-up flow requirements in future years as growth in the District's demands
occurs needs to consider average flow requirements when comparing make-up flow requirements
to the 1500 ac-ft/yr and 3000 ac-ft/yr threshold values. Computing a 10-year running average of
make-up flow requirements would provide a means of properly accounting for the hydrologic
variations which will influence make-up requirements in any given year. A 10-year running average
is consistent with terms and conditions often used in Colorado water rights transfers in which
transferred rights may exceed historical average diversions in any one year, but may not exceed that
average on a 10-year running average basis. The 10-year running average concept is also consistent
with the RIPRAP and the Colorado River Compact.
3.3.6 Effects on Critical Habitat
3.3.6.1 Water Depths
As part of the development of flow recommendations for the 15-mile reach, the USFWS (1995)
~I evaluated the preferences of the endangered fish species to different types of habitat under varying
flow conditions. Preferred water depths by season and type of habitat were developed, and transects
measured by the USFWS were compared to these preferences to determine the relative availability
of the preferred habitats within the 15-mile reach. While only four sites, comprising 14.1 percent
of the length of the 15-mile reach were selected for the study, the USFWS found that 66.8 percent
of all squawfish radiotelemetry locations and 76.5 percent of all razorback sucker locations occurred
within these four sites. It was assumed that these four sites should therefore be representative of
habitat availability within the 15-mile reach.
'~ Using the USFWS recommendation from Table 2 of their report and the flow versus maximum
transect depth from Table 3 of their report, maximum depths were developed for each habitat type
for both existing conditions and future conditions, based on the adjusted historic and reduced flows
developed as discussed previously in this appendix. Maximum water depths at 13 different flow
rates were measured by the USFWS at each of 13 transects. The flows computed in this study were
related to these flow/depth measurements by interpolation of the USFWS values. Representative
transects were selected for comparison for each of the habitat types for which depth data were
provided -backwater, eddy, pool, fast run, and slow run. Where more than one transect was
~j available for a particular habitat, an attempt was made to select transects which were "average" for
that habitat type. For backwater habitat, the two measurements made by the USFWS in 1990 and
1991 (following spring flooding which scoured and deepened the transect channel bottom) were both
evaluated in this analysis.
The USFWS also developed average transect depths for each measured flow rate. However, these
values do not provide a meaningful relationship between flow and depth due to the irregular
geometry of most of the transects. In many cases, average depth decreased with increasing flow
rates due to large expanses of shallow areas at high flows. A habitat transect which is preferable
under low flow conditions might not appear to be preferable at high flows since the average depth
would be less than a minimum acceptable value.
CDM Camp Dresser & McKee