Figure 4. Major waterways with winter navigation in the United States.

Early winter flow regulation to control freezeup ice jam flooding

Table 2. Major discharge-regulated tributaries of the Upper Mississippi River

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Upper Mississippi River

Lake

Lake

Erie

New Cumberland

Dresden Island

Starved Rock

Pike Island

Willow River

Circled numbers indicate Lock and Dam numbers

Figure 4. Major waterways with winter navigation in the United States.

best ice management strategy is to rapidly form

relatively steady, creating ideal conditions for the

and maintain stable ice covers along the margins

formation of smooth ice covers. Winter navigation

of a smooth-sided navigation channel (Tuthill

may delay ice cover formation by continually

1998). This section examines current flow regula-

re-breaking the ice cover on the navigation chan-

tion and its effect on ice cover formation on the

nel and preserving open water areas where frazil

upper Mississippi and Illinois Rivers, as well as

ice can be produced. The broken ice may jam at

the potential for flow control for ice cover forma-

channel constrictions impeding navigation, or

tion on the Ohio River. The Illinois Waterway is

accumulate and cause problems upstream of locks

the preferred winter navigation route in the Mid-

and dams. These issues are addressed in the Mid-

west because ice conditions are relatively less

winter Period section, as is ice passage at naviga-

severe than on the upper Mississippi. The upper

tion projects during that time.

Mississippi is closed to winter navigation above

On the upper Mississippi and Illinois River

Lock and Dam 20, whereas the entire Illinois

basins, discharge-controlled tributary inflow

Waterway and Ohio River remain open to navi-

accounts for only a small portion of the total main

gation all winter. Figure 4 shows these rivers and

stem discharge during the freezeup period. Table

the locations of major navigation dams.

2 shows average winter flows from the two major

discharge-controlled tributaries of the upper Mis-

Illinois Waterway and

sissippi below Rock Island. These data indicate

Upper Mississippi River

that retaining all reservoir outflow during the ice-

Early winter flows on the Illinois Waterway

formation period would reduce the main stem

and Upper Mississippi River are typically low and

discharge by only about 5%.

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