9406

• UCREFRP Catalog Number: 9406
• Author: Osmundson, D. B.
• Title: Importance of the '15-Mile Reach' to Colorado River Populations of Endangered Colorado Pikeminnow and Razorback Sucker.
• USFW Year: 2000.
• USFW - Doc Type: Grand Junction.
• Copyright Material: NO

INTRODUCTION
The '15-mile reach' is that portion of
the Colorado River between the Grand
Valley Diversion Dam at Palisade, Colorado
and the confluence with the Gunnison River
near downtown Grand Junction (Fig. 1).
This reach is occupied by two endangered
fish species, the Colorado pikeminnow
Ptychochedus lucius and the razorback
sucker Xyrauchen texanus. Because the
15-mile reach is designated critical habitat
and is sometimes acutely affected by local
irrigation withdrawals of water, manage-
ment of the reach has received considerable
attention. Consequently, a need exists for a
document that describes the biological
importance of this reach and provides man-
agers a common understanding from which
issues can most effectively be addressed.
This report attempts to meet that need by
providing a synthesis of current information
pertaining to the role that the 15-mile reach
plays in providing habitat critical to the
viability and recovery of Colorado River
populations of endangered Colorado pike-
minnow and razorback sucker.
BACKGROUND
Water Use
Water withdrawals, beginning at the
turn of the century, have resulted in major
changes in the flow regime of the 15-mile
reach. Flows in both this reach and reaches
downstream have diminished because of
diversions of water used to meet local
irrigation needs as well as transbasin diver-
sions of water from west slope headwaters
to metropolitan areas of Colorado's east
slope. The likelihood of additional water
depletions upstream of this reach is certain
because the State of Colorado has ex-
pressed its intent to pursue full utilization of
its apportioned share of Colorado River
water, as set forth in the 1922 Colorado
River Compact and the 1948 Upper Colo-
rado River Compact. These multi-state
agreements were formulated prior to soci-
etal concerns for environmental quality or
the enactment of the Endangered Species
Act. Consequently, the conflicting demands
of water development and protection of
endemic Colorado River fishes has resulted
in an institutional tug-of-war over water
flowing through the 15-mile reach. The
Fish and Wildlife Service, recognizing the
importance of the 15-mile reach, recently
issued a programmatic biological opinion
that stipulates the implementation ofvarious
recovery actions designed to offset the
negative effects of past and future water
depletions. Thus, additional depletions will
be in compliance with the Endangered
Species Act, provided that the recovery
actions are implemented in a timely manner
and a positive fish population response is
detected.
Endangered Fish Use
As the name implies, this section of
river is roughly 15 miles (24 km) long and
runs through the upper half of the Grand
Valley. The Grand Valley, extending ap-
proximately 3 5 miles (56 km) from Loma to
Palisade, Colorado, is an alluvial valley
containing the largest urban area and one of
the largest farming areas in western Colo-
rado. Razorback suckers, though rare, were
captured throughout the Grand Valley in
the late 1970s and early 1980s, primarily in