Volume 201: Lake Winnebago – An Important Great Lakes Resource

Physical Characteristics and Uses

Lake Winnebago lies within the largest drainage 

basin to Lake Michigan and the third largest to the 

Great Lakes. The red shaded area in the image 

below (Figure 1) illustrates the basin size and 

location within the Great Lakes. 

Figure 1: Fox-Wolf River Basin Location

Lake Winnebago is the second largest freshwater 

lake within any state in the United States (second 

to Lake Okeechobee in Florida). The Wisconsin 

lake is about 28 miles (45 km) long and 10 miles 

(16 km) wide with a surface area of about 206 

square miles (534 km2

). It is part of the Fox-Wolf 

River Basin which has an area of 6,430 square 

miles (16,650 km2). Water flows into Lake 

Winnebago from the Wolf River and Upper Fox 

River, then out of the lake through the Lower Fox 

River and into Green Bay (Figure 2). 

The Wolf River originates in the central part of 

Forest County, Wisconsin, and flows in a southerly 

direction through Lake Winneconne, Lake Poygan 

and several smaller lakes (known as the upper 

pools). The Upper Fox River flows through flat 

marshy areas, many with poor drainage. The 

higher grounds surrounding the floodplain are 

generally good quality agricultural lands, chiefly 

devoted to dairy farming.

Figure 2: Fox-Wolf River Watershed

The Wolf, Upper Fox, and Lower Fox Rivers, 

along with Lake Winnebago and the other upper 

pool lakes, serve as vital water resources to the 

region. They are used for a variety of commercial, 

industrial, municipal, environmental, and 

recreational purposes. Boating, fishing, and 

hunting, are becoming increasingly popular across 

the basin. Lake Winnebago, with its many access 

and launch facilities, is a popular destination for 

those looking to fish, pleasure boat, and water ski. 

These activities are making increasing demands on 

the region's lakes and rivers. 

Great Lakes

Update
Vol. 201 Great Lakes Update October 2018

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The Fox-Wolf River basin is used by public water 

utilities and local governments for domestic water 

supplies and for services such as fire-fighting and 

street washing. About 20 percent of the water 

withdrawn in the basin is used by public water 

utilities and local governments for domestic water 

supplies, commercial and industrial uses. The four 

communities of Appleton, Oshkosh, Neenah, and 

Menasha depend on water supplies from Lake 

Winnebago; others depend primarily on 

groundwater.

The water resources of the region are extensively 

used for recreational activities, particularly 

fishing, hunting and boating. These activities are 

increasing demands on the region's lakes and 

streams. The majority of boating use, primarily for 

fishing, pleasure cruising, and water skiing, is 

concentrated around those lakes having adequate 

access, water depths and launching facilities. 

Because of its size and character, Lake Winnebago 

provides the widest range of boating opportunities. 

The heavy concentration of boaters will continue 

to increase in the future, bringing increased 

demands for mooring facilities and associated 

services. 

The demand for increased recreational activities 

may also impact environmentally sensitive areas 

adjacent to, and in the rivers and lakes of the Lake 

Winnebago region. Fluctuations in lake levels, ice 

and agricultural practices in the watershed have 

caused the loss of many acres of wetland habitat. 

The losses have had a direct impact on the 

abundance and diversity of fish and wildlife. 

Each group – municipalities, public utilities, waste 

treatment plants, industries, and recreational users 

– who use Lake Winnebago and the surrounding 

waterways have a stake in the quantity and quality 

of the water resource. Often, one group’s desires 

for specific water levels and discharges are in 

conflict with another group’s needs. For example, 

recreational users want to maintain higher water 

levels in Lake Winnebago for boating, fishing, 

sailing and water skiing, whereas higher water 

levels in the early spring can cause serious 

environmental damage to sensitive aquatic 

vegetation. 

History of Lake Winnebago Regulation

In the 1850s, Lake Winnebago became part of an 

important commercial navigation system that 

connected Green Bay with the Mississippi River. 

To facilitate navigation, dams were built on the 

Fox River at Neenah and Menasha, creating Lake 

Winnebago and the upper pool lakes of Lakes 

Poygan, Winneconne, and Butte des Morts. A 

system of locks and dams was also constructed 

along the lower Fox River to make navigation 

through the lower Fox River to Green Bay 

possible. 

The construction of dams on the Lower Fox River 

spurred the development of hydroelectric power 

generation at many of these dams. The pulp and 

paper industry facilities line the banks of the 

Lower Fox River that drops 168 feet (51 m) over 

40 miles (64 km) from Lake Winnebago to Green 

Bay. These industries use the river for their process 

and cooling water supply. 

Figure 3: Paper Mill on the Fox River
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Floods have occurred in the adjacent reaches of the 

Fox River and along the shores of Lake 

Winnebago during all seasons of the year, with the 

most extensive flooding occurring in spring. The 

Wolf and Upper Fox Rivers generally require 

several days of precipitation or snow melt-off to 

reach flood stage. Uncontrolled inflows to Lake 

Winnebago from these rivers during flood stage 

can result in gradual and sustained rises in the lake 

level for a week or more. More abrupt rises in the 

level of Lake Winnebago are primarily due to 

heavy localized precipitation on the water surface.

Figure 4: Spring 2018 flooding on the Wolf River 

near Shawano

In order to manage the risk of flooding in the basin, 

the Marshall Order was established in 1886 to 

“maintain the level of Lake Winnebago at or 

below” flood stage (3.45 feet Oshkosh Datum). 

Oshkosh Datum is a local datum referenced to the 

crest of the Menasha Dam from which all Lake 

Winnebago water surface elevations are 

derived. In 1920, the Marshall Order was 

modified to address navigation needs on Lake 

Winnebago by defining “...limits of regulation for 

Lake Winnebago under existing laws, orders, rules 

and permits are from 21-1/4 inches above the crest 

of Menasha Dam (3.45 feet Oshkosh Datum) down 

to the crest during the navigation season (1.68 feet 

Oshkosh Datum). The navigation season presently 

extends from about 1 May to early October. Figure 

5 shows the typical water level strategy used for 

regulating the level on Lake Winnebago annually. 

During the years the Corps has regulated the lake, 

water levels have predominately remained within 

the limits of the Marshall Order. 

Current Regulation Strategy

The U.S. Army Corps of Engineers, Detroit 

District regulates Lake Winnebago water levels on 

a daily basis, attempting to balance the needs of all 

competing uses of the basin’s water resources. 

This is accomplished through frequent 

coordination, discussion and correspondence with 

the user communities and conducting an annual 

regulation meeting that is open to the public. 

During the annual meeting, input from the public 

is taken into consideration when establishing the 

water level strategy for the coming year. Figure 5 

shows a typical water level strategy that meets the 

criteria of flood risk management (the Marshall 

Order) and balances the needs of the stakeholders. 

An important objective of lake operations is to 

reduce downstream flooding during spring 

snowmelt and floods. The lake is drawn down in 

the winter in anticipation of spring rains and 

snowmelt. The lake’s storage capacity allows it to 

be used to reduce the incidence of downstream 

floods. After the threat of spring flooding has 

passed, the lake level is raised to its summer target 

for navigation and recreational boating. 

In the winter after a solid ice cover forms in the 

upper reaches of the Lake Winnebago pool, the 

Corps of Engineers begins a slow drawdown. The 

drawdown provides storage needed to contain 

spring flooding. For the sake of the aquatic and 

semi-aquatic animals that occupy the shallowwater zone during the fall and winter, the water 

level is not drawn down before a solid ice cover 

develops. 
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Figure 5: Lake Winnebago Water Level Strategy

Once the drawdown target is achieved, the stage is 

held constant until the ice cover in the Lake 

Winnebago pool breaks up and starts moving out.

It should be noted that the drawdown target can be 

altered to a level below the Marshall Order 

because it occurs during the non-navigation 

season. The horizontal light blue line in Figure 5 

represents about a one month timeframe when ice 

out has occurred over the past 10 years. 

Once the ice has left the lake, the spring refill of 

the Winnebago pool begins. The pool is refilled to 

achieve the target navigation level in late spring

(typically June 1). In recent years, the spring refill 

has been accomplished in a more gradual manner 

to avoid excessively high levels that can cause 

serious environmental damage to aquatic plants. 

The level of Lake Winnebago is held as close as 

possible to the target stage during the remainder of 

the navigation season. Daily reviews and analyses 

of current basin conditions and forecasts are 

performed to keep the 206 square mile lake within 

the 2.5 inch green band of the graph. Despite 

efforts, the lake has been both above and below the 

target at times. Heavy precipitation can cause 

uncontrolled inflows to soar above maximum 

outflow capacity causing the level to climb 

quickly. On the contrary, the stage may fall three 

or four tenths of a foot below the target due to lack 

of precipitation and increased evaporation. When 

navigation season ends, the lake is drawn down 

again, aiming for a level of about 2.5 feet Oshkosh 

datum by mid-October. 

The Army Corps of Engineers works closely with 

the WiDNR, U.S. Fish and Wildlife Service, local 

municipalities, hydroelectric users, wastewater 

regulators, and other groups to establish specific 

regulation strategies and to facilitate cooperation 

between the various users of the basin’s water 

resources.