9299

• UCREFRP Catalog Number: 9299
• Author: Anderson, R. and J. Mumma.
• Title: Aspinall Studies
• USFW Year: 1999.
• USFW - Doc Type: Annual assessment of Colorado Pikeminnow Larval Production in the Gunnison and Colorado Rivers, Colorado 1992-1996.
• Copyright Material: NO

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STUDY AREA

The study area included portions of the Gunnison and Colorado rivers within
Colorado that are occupied by Colorado pikeminnow (Figure 1). The Gunnison River is a
major tributary and flow in the Gunnison River has been altered by a series of three large
reservoirs collectively called the Aspinall.unit. This project has altered the magnitude of
spring runoff and the timing and temperature of flow. The Gunnison River contributes
about 40 percent of the total average annual flow to the upper Colorado River at the
Colorado-Utah state-line (Ugland et aI., 1996). Redlands diversion dam, constructed in
1918, is located 2.3 miles upstream of the confluence. This structure typically removes
about 700 cfs from the river. A gauge below the Redlands dam began operation in 1995.
Prior to 1995 flow below Redlands dam was estimated by subtracting 700 cfs from the
Whitewater gauge. The Whitewater gauge is located 8 miles southeast of Grand Junction
(RM 13.6, RK 21.9) and was used to represent flow at the stations above the Redlands
diversion. The study area in the Gunnison River is from Bridgeport (RK 35.0)
downstream to the confluence with the Colorado River.

The study area in the Colorado River is from Palisade, Colorado (Grand Valley
Diversion at RM 185.4, RK 298.3) downstream to the Colorado-Utah state line (RM
131.8, RK 212.0). The Colorado River in this area consists of the 15-Mile Reach [mouth
of the Gunnison River (RM 171.0/RK 275.1) upstream to Palisade], and from downstream
from the Gunnison River to the Colorado Utah state line, about 39 miles. The 15-Mile
Reach is dewatered by two major upstream diversion structures, the Government Highline
diversion, located in lower Debeque Canyon, and the Grand Valley diversion dam located
3.2 miles downstream of Government Highline diversion. Together these structures divert
about 1200-1600 cfs at the upper end of the reach. A USGS gauge is located about 0.25
miles downstream from the intake for the Grand Valley Diversion Canal. Since the 15-
Mile reach is upstream of the confluence of the Gunnison, this reach is not directly
effected by operations related to the Aspinall Unit.

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