FLOOD08553

• County: Ouray
• Community: Ouray
• Stream Name: Uncompahgre River
• Basin: Gunnison
• Title: Draft Environmental Assessment Ridgway Dam and Reservoir Water Control Manual
• Date: 4/1/1996
• Prepared For: State of Colorado
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Project

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3.4 Future Conditions With and Without Project.

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3.4.1 Future Conditions With Project. For the area around the reservoir or
downstream from Ridgway Dam, future environmental conditions with the water
control manual would not significantly change. Water releases are more controlled to
provide flood protection and reduce risk of damage, but could potentially cause some
slight environmental impacts with the timing of releases. Environmental conditions.
could change slightly around the reservoir and below the dam when water is held less
often and for shorter periods and when water levels fluctuate. Under the proposed
with-project condition, Ridgway Reservoir would be operated essentially the same as it
has been since 1988, when it began filling with water, The effects of the timing,
duration, and frequency of releasing water on the environment are discussed in Section
5.0, Environmental Effects,

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3.4.2 Future Conditions Without Project. For the area around the reservoir
or downstream from Ridgway Dam, future conditions without the water control manual
would also riot significantly change the environment. The USBR would probably
continue to manage flood control as it has in the past. Holding water more often and
for longer periods could slightly benefit the fishery and vegetation in the reservoir and
below the dam. However, below the dam, the timing, duration, and frequency of
releasing water could cause flood damage to the environment and private lands. The
USBR's flood control operations may increase the risk of flood damage if a major
storm or snowmelt were to occur when the reservoir is full or near capacity.
Environmental conditions below the dam could change slightly when more water is
released because the reservoir is full or near capacity. The effects of the timing,
duration, and frequency of releasing water on the environment are discussed in Section
5.0, Environmental Effects.

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4.0 ENVIRONMENTAL SETI'ING

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4.1 Climate. The Uncompahgre River Basin is mostly semi-arid, with an average
annual precipitation range from approximately 10 inches at Montrose tj) 16 inches at
Ridgway State Park to 22 inches at Ouray, The prevailing wind is from the west-
southwest, although a wide range of surface winds are influenced by the specific local
topography. The frost-free period (consecutive days with minimum temperatures above
320 Fahrenheit) averages 112 days near the reservoir. The average monthly
temperatures range from a minimum of about 150 Fahrenheit in January to an average
high temperature of about 90" Fahrenheit in July.

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4.2 Topography. The Uncompahgre River Basin is bounded on the west by the
Uncompahgre Plateau. Horsefly Peak, at the southern end of the plateau, is the

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