PROJ01838

• Contract/PO #: C153605
• Contractor Name: U. S. Bureau of Reclamation
• Water District: 0
• County: Mesa
• Loan Projects - Doc Type: Feasibility Study

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Spillway

The spillway would be located on the left abutment of the
dam with a discharge capacity of 13,940 ft3/sec at maximum water
surface elevation of 8308.8 feet. The spillway would consist of
an ogee - crest intake having a crest length of 100 ft., a
reinforced concrete chute structure, and a Type II stilling
basin. The 1967 feasibility design had a spillway crest length
of 25 feet. A bridge would be. located over the spillway crest
for the relocated forest development road.

Operations StudY

A current operations study was conducted by the Denver
Office (Appendix 1). The study was conducted utilizing past
streamflow, climatological, and diversion records in order to
determine end of month (EOM) content of the reservoir. Two
complete iterations were conducted by the Denver Office.

The first iteration was conducted to determine the firm
yield based on a 25,240 ac-ft reservoir and a uniform demand
hydrograph. The monthly demands were initially projected through
interviews of the project sponsors and are shown in Appendix 1.
The initial yearly demand of 15,200 ac-ft included 6,000 ac-ft
for the endangered fish Recovery Implementation Program and 9,200
ac-ft for the project sponsors. However, a demand of 15,200 ac-
ft was greater than the resultant 10,200 ac-ft firm yield of the
reservoir. The critical period of study, at which time the
minimum EOM of 3,200 ac-ft content would occur, was July 1952 -
March 1957.

The second iteration was conducted using a "perfect
projection" of water supply and a 25,240 ac-ft reservoir. Three
different demand hydrographs for wet, normal, and dry years were
developed to reflect changes in demand that would occur based
upon snowpack and runoff information. If the total annual runoff
for the year in question exceeded 20,000 ac-ft it was considered
a wet year, under 10,000 ac-ft was considered a dry year, and
10,000 to 20,000 ac-ft was considered normal. The annual summary
of this iteration is shown in Appendix 2. The results of this
iteration show a dry year yield of 9,200 ac-ft, wet year yield of
12,700 ac-ft and a normal year yield of 11,400 ac-ft.

The third iteration was a cursory study conducted by the
GJPO using the spreadsheet provided by the Denver Office. It
assumed that the maximum reservoir capacity was 10,000 ac-ft and
the minimum in-active pool was 1,500 ac-ft. No adjustment was
made for change in evaporation due to the reduced reservoir size.
The firm yield for these conditions was 6,000 - 7,000 ac-ft. The
critical period being the mid 1970's at which time the reservoir

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