BOARD00185 ‎(2)‎

• Board Meeting Date: 5/23/2007
• Description: Intrastate Water Management and Development Section - Water Supply Reserve Account Applications for Grants
• Board Meetings - Doc Type: Memo

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Water Supply Reserve Account - Grant and Loan Program
Water Activity Summary Sheet

Applicant: Hinsdale County and the Upper
Gunnison River Water Conservancy District

Water Activity Name: Lake San Cristobal
Control Outlet Structure Project

Water Activity Purpose: Technical Analysis
regarding permitting feasibility study
/Environmental Compliance (see
Issues/Additional needs discussion)

Amount Requested: $35,000.00

Source of Funds: Basin

Matching Funds: None

County: Hinsdale
Drainage Basin: Gunnison River
Water Source: Lake Fork Gunnison River

Water Activity Summary:

Hinsdale County and the Upper Gunnison River Water Conservancy District (UGRWCD) are examining the
feasibility of constructing a new permanent control structure at the outlet of Lake San Cistobal. The control
structure would regulate the lake level to provide releases of water from the lake and prevent failure of the
lake outlet structure during flood events. The stored water resulting from this project will be used primarily
as augmentation water within the Lake Fork of the Gunnison River. Other beneficial uses may include
agriculture, recreation and possibly releases for instream flow purposes.

The feasibility study will consist of two analyses that will be performed simultaneously:

1. Estimate the firm yield of the 960 acre-feet of storage and develop an engineering report to support
the water right application in case no. 03CWI08 and,
2. Analyze the current and future market for water impounded by the structure.

According to the application, in 2003, a feasibility study was conducted to examine the potential enlargement
of Lake San Cristobal. This study stated that in the 1950s the lake was altered from its natural condition
when the Hinsdale County Road and Bridge Department constructed a rock and timber dam at the outlet.
Two significant issues were made apparent in this study. First, there were significant wetlands on the
perimeter of the lake which would be inundated by the proposed enlargement. The mitigation of these
wetlands appeared to be cost-prohibitive for the project. In addition, the Colorado Water Conservation
Board holds a Natural Lake Level (NLL) water right on Lake San Cristobal (4-77W3366) with an
appropriation date of May 12, 1976 with an elevation of 8995.0 feet. After further investigation, it was
determined that the dam constructed in the 1950s raised the lake elevation to 8992.5 feet from its natural
elevation of 8990.0 feet. Based on these findings, the applicants believe that the NLL on Lake San Cristobal
is incorrect and should be modified pursuant to Rule 9c (1) of the Rules Concerning the Colorado Instream
Flow and Natural Lake Level Program. It should be noted that in 2003, the Upper Gunnison River Water
Conservancy District claimed the additional 960 acre-feet impounded by the dam in water right application