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C150221 Water Potential Report
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C150221 Water Potential Report
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Last modified
6/12/2014 4:51:05 PM
Creation date
2/19/2014 3:15:10 PM
Metadata
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Template:
Loan Projects
Contract/PO #
C150221
Contractor Name
San Luis Valley Irrigation District
Contract Type
Grant
Water District
20
County
Hinsdale
Loan Projects - Doc Type
Report
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MEMORANDUM OF UNDERSTANDIN J 0 tai 2 4 1999 <br /> •FOR TILE OPERATION OF RIO GRANDE e , IR <br /> FOR DAM SAFETY PURPOSES <br /> INTRODUCTION <br /> The San Luis Valley Irrigation District (the "District") owns Rio Grande Reservoir(the <br /> "Reservoir")which was constructed in the early 1900s,and is located in Hinsdale County,Colorado. <br /> Because of the date of construction,the Reservoir is considered a pre-Compact reservoir under the <br /> Rio Grande Compact. 'The Reservoir's pre-Compact status provides a tool that can be used at times <br /> to benefit water users diverting from the Rio Grande and to aid the State of Colorado(the"State") <br /> in meeting the Rio Grande's separate Compact obligations. By separate agreements, the State has, <br /> on occasion,used the Reservoir to help minimize over deliveries under the Compact. The Reservoir <br /> is the only Rio Grande mainstem reservoir in Colorado and controls approximately 25% of the Rio <br /> Grande's flow above the Del Norte gage. The Reservoir inflows typically must be passed to satisfy <br /> downstream demand unless the Reservoir storage decrees are in priority. Its safe and prudent <br /> operation, therefore, is critical for water rights and Compact administration. <br /> In 1 987,to meet federal and state dam safety standards,the District substantially rehabilitated <br /> the Reservoir's downstream outlet gates(the"gates"). Recognizing the Reservoir's importance,the <br /> Colorado Water Conservation Board funded the District's 1987 rehabilitation work through a grant <br /> and loan package. The rehabilitation included the installation of new liner sections and three new 2 <br /> feet by 7%z feet gates. The combined release capacity at the gates is approximately 3,000 cubic feet <br /> per second("cfs"). Because of historical restrictions in the tunnel downstream ofthe gates,the actual <br /> release capacity is approximately 2,500 cfs. The 1987 rehabilitation did not modify the Reservoir's <br /> outlet tunnel downstream of the gates. <br /> Between 1987 and 1996,releases through the outlet tunnel occasionally exceeded 1,500 cfs <br /> for short periods of time. In the 1997 runoff season, severe vibrations and noise originating from the <br /> outlet works were reported when releases exceeded 1,500 cfs. Subsequent inspection revealed <br /> damage to the Reservoir's outlet works created by the turbulent hydraulic conditions in the outlet <br /> tunnel. In 1997, the District made the necessary tunnel repairs at a cost of$75,000.00. <br /> In the opinion of the District's engineering consultant, HARZA Northwest, Inc. <br /> ("HARZA"),this turbulent hydraulic condition occurs at flows between approximately 1,500- 1,900 <br /> cfs. HARZA has concluded that ifthese flow rates are reached and maintained, damage to the outlet <br /> works may occur and unsafe operating conditions may result. HARZA also has calculated that <br /> release rates of approximately 2,000 cfs or more will pressurize the outlet tunnel with water and the <br /> turbulent hydraulic condition may be greatly reduced or eliminated. When fully pressurized,HARZA <br /> estimates that the maximum release rate through the outlet tunnel is approximately 2,500 cfs. The <br /> release rate limitation of the Reservoir's outlet tunnel could, in unusual circumstances, reduce the <br /> water supply legally and physically available to downstream senior water rights and impact the Rio <br /> Grande's Compact deliveries. <br /> Page 1 of 5 <br />
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