Table 4. Flow-control objectives; ice-formation period.
Maximize
winter
Benefit
Control
hydroelectric
winter
ice jam
River; structure
production
navigation
flooding
St. Lawrence River; Beauharnois Canal
Primary
St. Lawrence River; International Section
Primary
Jenpeg Diversion, Lake Winnipeg Regulation
Primary
La Grande River Complex
Primary
Allegheny River; Kinzua Dam
Primary
Illinois River Navigation Dams
Upper Mississippi River Navigation Dams
Upper Ohio River Dams and Flood Control Projects
Possible
Table 5. Flow-control objectives; midwinter period.
Maximize
Control ice jam
winter
flooding/
Ice flushing/
Water supply/
hydroelectric
maintain
winter
in-stream flows
River; structure
production
ice cover
navigation
for fish
Missouri River; Oahe Dam
Primary
Primary
Yukon River; Whitehorse Rapids Dam
Primary
Primary
Upper Niagara River; Niagara Falls Diversions
Primary
Primary
Ohio River Navigation Dams
Secondary
Secondary
Primary
Upper Mississippi River; Locks and Dams 2026
Secondary
Secondary
Primary
Illinois River; Navigation Dams
Secondary
Primary
Missouri River; Gavins Point Dam
Primary
Green River, Utah; Flaming Gorge Dam
Primary
Primary
South Fork Shoshone River; Buffalo Bill Dam
Secondary
Primary
for water supply and fish. Table 5 lists flow-
stage increases above the freezeup water level
control objectives at projects described in this
could produce ice jam flooding and possibly
report.
break up the ice cover.
With estimates or measurements of ice thick-
Flow-control guidance for preventing
ness and roughness, numerical models such as
midwinter breakups and ice jams
HEC-2 and UNET can predict ice-affected stage
Hydroelectric producers often must constrain
rise under different discharge scenarios. The like-
the magnitude of their flow increases following
lihood of a planned flow release causing a mid-
ice cover formation, and limit the amplitude of the
winter breakup can then be assessed, based on
hydroelectric peaking cycle to minimize midwin-
knowledge of local ice processes or the above-
ter breakups and ice jam flooding. Owing to a lack
mentioned rules of thumb. Further development
of practical engineering tools for predicting river
of Ferrick and Mulherin's (1989) breakup model
ice breakup, hydroelectric plant operators rely on
would improve the capability for predicting mid-
observation and experience rather than theoreti-
winter breakup and provide a flow regulation
cal methods to avoid breaking up the ice cover
planning tool for project operators.
and causing ice jam floods. The rules of thumb
Recent studies by NYPA and OH have improved
that exist are not easily transferable from site to
the understanding of the relationship between
site. For example, Donchenko (1978) observed
project operations and ice jamming on the Upper
that stage must rise 3 to 4 times the ice thickness
Niagara River. Study results were based in part
above the freezeup water level to break up the ice
on a model developed by Shen et al. (1997) that
cover on some Russian rivers. Breland's (1995)
accurately simulated ice transport and jamming
observations on the upper Yukon River were
under a range of operational scenarios. This
more conservative, predicting that midwinter
model would be a useful tool in future studies
22
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