WSP06255

• File Number: 8240.200.47.G
• Description: Silt Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1997
• Author: USDOI/BOR
• Title: Silt Project - Final Appraisal Report
• Water Supply Pro - Doc Type: Publication

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Chapter 3 - Identification and Analysis of Options

Rifle will continue, and any potential for Rifle Gap Reservoir to help reduce
flood damages will not be utilized.
. The endangered fish will have to be recovered using other resources in the
Colorado River basin. Failure of the proactive Recovery Program may make
future development of water difficult or impossible if Federal funding or
approvals are required. Any future actions or changes related to Silt Project
operations may be limited by Endangered Species Act considerations.
. Maintenance of the Colorado River diversion will continue to be difficult and
costly.

Table 2 displays the options that the work group identified to improve recreational
opportunities at Rifle Gap Reservoir and an analysis of those options. The
effectiveness of the options can be judged based on their ability to achieve State
Parks' goal of maintaining 4,200 af of water in the reservoir (total storage
including inactive portion) through Labor Day (i.e. 5 feet above the bottom of the
boat ramp). Based on records of historical reservoir levels, the amount of water
needed to maintain that level ranges from 0 to about 2,500 af per year depending
on hydrologic conditions.

Table 3 displays options to improve flood control. One way to judge the
effectiveness of these options is to examine their capability to free up or develop
storage space for flood flows in Rifle Gap Reservoir. A storage space sufficient to
address the flood control needs has not been computed, as yet. Additionally, a
study is needed to determine effects of reducing the 310 cfs discharge from
outlet works & uncontrolled spill from Rifle Gap Reservoir on flows through Rifle.
Note that using Rifle Gap for flood control may conflict with meeting other needs
such as storing water for the benefit of recreation and/or endangered fish and vice
versa.

Table 4 displays options for assisting with endangered fish recovery, which do so
by providing water that can be delivered to the 15-Mile Reach. Many of these
options are the same or similar to options aimed at improving recreational
opportunities. For the sake of brevity, the reader is asked to refer back to Table 2
for information on some of the options. The effectiveness of these options can be
judged based on their ability to help satisfy the need for supplement flows in the
15-Mile Reach, the total need of which is estimated to range from 33,000 to
168,000 af, annually [pers. comm. George Smith, FWS]. Please note that use of
storage in Rifle Gap Reservoir and delivery for this purpose must avoid injury to
other water users if the existing project water rights are to be used.

Table 5 displays options to address the need for domestic water supply. Some of
the nine displayed options are not directly comparable. The first 2 options - pipe

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