SouthPlatteComments11

• Basin: South Platte
• Title: Comments 11
• Date: 12/12/2003
• SWSI - Doc Type: Comments

Cheesman Reservoir, built in 1905, was the world's highest dam of its type at the time of
construction and Denver Waterts first mountain reservoir. It is designated a National
Civil Engineering historic landmark. It has a gravity arch masonry dam capable of
impounding 79,064 acre-feet of water~ The reservoir is open to limited recreation..
Cheesman is the Hworkhorse" of Denver Water's South Platte system which serves
hundreds of thousands of customers in the Denver area. Cheesman Reservoir typically
fills with the spring runoff. Water is released from storage to meet customer needs
throughout the summer and winter with the reservoir typically reaching its lowest
contents before spring runoff~ Cheesman Reservoir provides water to Denver Water's
Foothills and Marston Treatment Plant. Water can also be supplied to those plants with
water from Dillon Reservoir via the Roberts TunneL Generally the Roberts Tunnel is
operated to supplement Denver Water's South Platte supply (Figure l)~ There are no
formal minimum streamflow requirements below Cheesman Reservoir.

Cheesman has five valve runs, all built in 1971. They operate properly and are restricted
to the normal openings between 20 percent and 80 percent

Capacity: With a full reservoir, the spillway capacity at elevation 6850.91 is 22,370 cfs,
the valve house capacity is 1,581 efs, the Johnson valve capacity is 800 cfs.

There are three general factors affecting Cheesman's operation. 1) Cheesman is operated
to fill, if possible, each spring~ 2) Releases are made from storage lowering the reservoir
as needed to meet customer water use throughout the year.. Because there is limited
downstream storage between Cheesman Reservoir and the water treatment plants to act as
a buffer, releases from Cheesman Reservoir generally coincide with changes in water use.
3) Releases are also affected by water rights administration~ (See the water rights section
for more detail.) When Cheesman Reservoir is out of priority, it is required to bypass all
of the natural inflow to the reservoir unless an exchange can be made using downstream
water to replace the water that is stored in Cheesman Reservoir. Cheesman Reservoir has
limited opportunities in the springtime to store water. Any water that can be stored, but is
not, may be counted against Cheesman's water right by the State and is a potential loss of
supply. In Section II~C.2i' mainstem fishery, reservoir operations of making storage
releases are mentioned provided those waters can be recovered. Under current operation
of Denver Water's system, at times releases into Chatfield could not be recovered and for
water quality management there may be times when level in Marston is held below full.
. Strontia Springs Reservoir, downstream of the confluence of the South Platte River
mainstem and the North Fork, provides a small regulating facility for Denver Water and
Aurora~ The reservoir holds 7,700 acre-feet when full. It has 20 feet of elevation or
about 2,000 acre-feet of operating range.

Roberts Tunnel:

Denver Water provides storage water from Cheesman Reservoir or Dillon Reservoir to its
customers recei ving water from its South Platte system~ Dillon Reservoir water is

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