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

1
return flows and to a lesser de ree b the use of consum tive use transfer water reduced eva oration
g Y p ~ P
~ from the Jerry Creek reservoirs, replacement reservoir releases, and future municipal return flows.
In summary, under the District's Scenario C demand projection, municipal water use is expected to
increase from historic levels by 21,644 ac-ft/yr in the yeaz 2045, with a corresponding increase in
municipal return flows of 15,326 ac-ft/yr. Net diversions from the Colorado River Basin will
increase by 18,521 ac-ft/yr. The future net depletions from the Colorado River Basin in the'yeaz
2045 would therefore be expected to average 3,195 ac-fdyr.
3.3 HYDROLOGIC EFFECTS WITHIN THE 1 S-MILE REACH
3.3.j General
Previous informal consultation meetin s with the USFWS indicate that in addition to overall
g
depletions to the Colorado River Basin, they aze specifically concerned with hydrologic effects on
the habitat of endangered fish species within the 15-mile reach. This reach of the Colorado River
starts just below the Grand Valley Canal diversion and Orchard Mesa Powerplant tailrace, near
Palisade, Colorado and extends to the junction of the Colorado and Gunnison Rivers. (See Figure 1
in the Biological Assessment.)
At the request of the BLM, CDM has conducted an analysis of the historical flows at the top of the
15-mile reach and the effects that the District's future diversions will have on those flows and the
habitats of the endangered fish species. Return flows associated with septic systems and outdoor use
from the District's water users will begin to appear within the 15-mile reach. Therefore, the flow
reductions at the top of the reach represent the maximum flow reductions to Colorado River flows
in the 15-mile reach. Per agreements during informal consultation with the USFWS, the hydraulic
effects at the top of the 15-mile reach will be used to assess maximum effects in designated Colorado
River critical habitat. This is a conservative approach which simplifies the analysis and allows for
comparison with USFWS flow recommendations at the top of the reach.
e analysis entailed developing a record of lustoncal Colorado River streamflows at the top of the
15-mile reach, adjusting these flows for prior Section 7 consultations, as directed by the USFWS,
computing the expected reductions in those flows and corresponding habitat depths and azeas
resulting from the District's future diversions upstream, and compazing the adjusted historical and
reduced future flows, habitat depths, and areas to USFWS recommendations (USFWS 1995).
Effects were evaluated on a monthly basis using available USGS gaging records, Colorado Division
of Water Resources diversion records, and the District's raw water supply system model. This
model predicts what monthly diversions by the District's vazious appropriations would have been
to meet future system demands based upon hydrologic conditions during the period of 1975-1993.
During this period all such information was concurrently available.
CDM Camp Dresser & McKee
0:8047-1 IO~DOCIAPPEND-B.DOC B-9