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Lower Fox River Green Bay Major Tributaries of the Bay Geology Water Movement fluctuating water levels seiches currents residence times Links to More Information References

Looking south upstream from the mouth of the river  at the City of Green Bay.

Freshwater

Largest tributary to Green Bay

Flows north from the outlet of Lake Winnebago. 

Length --- 39 miles (64 km)

Contributes most of the pollution to Green Bay.

Highest concentration of pulp and paper mills in the world. (24 mills on 39 miles of river.)

Drainage basin --- roughly 6,250 square miles of land surface. (about 16,000 square km) Most of the area (about 90%) is located upstream of Lake Winnebago. About 1/3 of the total basin has become reforested.

Average annual flow ---Fox River from Lake Winnebago to Green Bay ---116m3/sec-1. Typical annual maximum and minimum flows are 340 and 55 m3s-1 respectively. 

Elevation drop --- 167.32 feet (51 meters) in only 39 miles of river. Prior to dam construction, the river had many sizable rapids.

Impounded by 12 dams and navigable through 17 locks. 

Waters from the Upper Fox River, Wolf River, and Lake Winnebago empty into the Lower Fox River at the outlet of Lake Winnebago. Lake Winnebago is the largest inland lake in Wisconsin, with an area of approximately 212 square miles (550 sq. km) and an average depth of 13 feet (4 meters).

GREEN BAY Freshwater Largest bay of Lake Michigan Largest freshwater estuary in the world Oriented in a NNE-SSW direction Latitude & Longitude --- south end at city of Green Bay, 44° 31' N, and north end at Big Bay de Noc, 45° 54¢ N.

Looking north toward the mouth of the Fox River  flowing into Green Bay.

Length --- 120 miles (193 km)

Mean width --- 14 miles (22 km)

Average width --- 23 miles (37 km)

Average depth of the extreme lower Bay --- 6.5 to 9.8 feet (2-3 m)

Mean depth --- 65 feet (20 m)

Maximum depth --- 176 feet (53 m), located 4 miles (6.4 km) west of Washington Island

Area --- 186 square miles (4,212 square km)

Volume --- 11 cubic miles (70 square km)

Height --- about 580 feet above New York mean sea level (176 m), though levels have fluctuated widely

Age --- about 10,000 years, since the last glaciers receded

Watershed --- drains approx. 15,625 square miles (40,000 square km). One third of all land that drains into Lake Michigan drains through Green Bay first (though the bay itself has only 7.9% of Lake Michigan’s total surface area). Two thirds of the Green Bay watershed is in Wisconsin, one third in Michigan

Green Bay is open to Lake Michigan at the northeast side with Door County, Rock Island, Washington Island and St. Martin’s Island separating the two.

Temperature --- cools faster than Lake Michigan in the fall, and becomes thermally stratified earlier in the summer. The southern bay is more than 7° C warmer than the northern bay, and 12° warmer than deep lake water

Eleven rivers and streams drain into Green Bay. Of these there are only 5 of major importance. Three are in Wisconsin --- the Fox/Wolf Rivers, Peshtigo River and Oconto River. Both Michigan and Wisconsin areas drain into the Menominee, which forms the boundary between the two states. The Escanaba is the only major river entirely in Michigan, with the Whitefish and Ford Rivers of secondary importance. The Fox River is the most significant river because of its volume and pollution load. 

Additional pollution loads come from municipal sewage plants, urban runoff and farmland runoff in the Lake Winnebago and lower Wolf River region. While the Fox River is the major source of degraded water, there are localized pollution problems in the Oconto, Peshtigo, Menominee and Escanaba Rivers. The smaller streams contribute significant loads of silt and debris, which vary in amount seasonally.

The northern bay has relatively high-quality (oligotrophic) waters, while the lower, southern bay has low-quality (hypereutrophic) water quality (though this has improved overall during the past 25 years.)

The region of the lower bay south of Long Tail Point, referred to as the "inner bay," has been described as an extension of the Fox River due to similar water quality features.

MAJOR TRIBUTARIES OF GREEN BAY

River        Length         Drainage Area          Mean Discharge

Fox                   322 km            16,687 sq. km               117 cu. meters/sec

Peshtigo             233                 2,991                            24

Oconto              209                 2,416                            16

Menominee         193                10,748                           88

Escanaba            185                2,382                             25

GEOLOGY

Green Bay is within the glaciated area of Wisconsin and Michigan. The Wisconsin portion is within the ancient lake system. The bedrock of the Green Bay area is paleozoic in age and composed of at least three formations, the Niagara (Dilurian, dolomite) of Door Peninsula, the Maquoketa (Ordovician, dolomitic shale) on the southeast shore, and the Platteville-Galena Group (Ordovician, dolomite and limestone) on the western edge of the Bay. Other important formations within the Bay’s watershed are the Prairie du Chien Group (Ordivician, dolomite), Cambrian sandstones and Precambrian granite and undifferentiated igneous and metamorphic rocks.

The post glacial history of Green Bay is one of advancing and retreating shorelines. 10,000 years ago, Lake Chicago, which occupied the present Lake Michigan Basin, was at about 600 feet in elevation (183 m), about 20 feet (6 m) above the present stage. The Lake drained southward and through the Chicago outlet. As the ice continued to retreat, the Lake Michigan and Lake Huron basins combined through the Little Traverse Bay Lowlands. The combined basins maintained an elevation of 605 feet (184 m) for almost 3,000 years. Distinct shoreline features developed during the period. At the end of the Algonquin period, about 7,000 years ago, Green Bay drained in four major steps until it was totally emptied. At least one beach may be evident 90 feet (27 m) below the present lake level.

Sixty-seven hundred years ago, with the bay completely drained, the west shore- rivers probably joined to form one great north flowing river. With Lake Superior at a much higher elevation, over 1,000 feet (303 m), a major drainage developed across Little Bay de Noc in Lake Michigan. This steep-walled channel is two miles wide and 100 feet deep (30.3) m) and extends across Northern Green Bay. That the bay filled rapidly to 605 feet (183 m) about 4,500 years ago is evidenced by the fact that little major deposition or erosion occurred in the former drainage channel.

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WATER MOVEMENT

Green Bay is best characterized as an estuary since it functions as a nutrient trap, has exceptionally high biological productivity, and because of the thermal and chemical differences between the water of its tributaries and that of Lake Michigan. It resembles the Delaware Bay estuary on the Atlantic Coast. The water in the bay has several characteristics important to management strategies:

• Fluctuating Water Levels --- Since 1860 when records were started, there has been a variation of over 7 feet between extreme high (1986) and low levels (1964), due to climatic variations. To a very limited degree the water levels can be controlled at the major inlet for Lake Michigan (Sault Ste. Marie) and through the southern outlet of the Chicago canal. Seasonal low water usually occurs in January, with higher levels occurring in June.

• Seiches --- Because of its elongated shape, Green Bay is subject to tilting, or basin oscillations, on a short-term scale, similar to tides but not on a regular schedule. Imagine water sloshing back and forth in a bathtub. These oscillations, or "seiches," (pronounced "saysh ez") are caused by wind, sudden changes in barometric pressure, currents and other physical factors. A normal seiche may change water levels a foot or more in a few hours, three or four times a day. The seiches are strong enough to reverse river flow up to 7 miles up from the mouth of the Fox River. In 1966, one seiche was measured with flows at the river mouth going upstream at a rate over 280 cubic meters per second (10,000 cfs) In 1957, the East River (a tributary of the Fox) had a change of 4.7 feet (1.33 m) in 17 hours, from a seiche pushing water upstream. The bay is also slightly affected by a semi-diurnal lunar tide as well.

• Currents --- Currents in the lower bay tend to be counter-clockwise, moving southerly on the western side, then swinging east and north. In addition, when the Fox River currents enter the bay they immediately turn east, due to the coreolis effect of the earth’s spin. Historically, the river currents kept the east shore of lower Green Bay flushed clean, with beautiful sandy beaches, while the west shore was quieter, accumulated more soft sediments and generated vast cattail marshes and wild rice beds. Some pockets in the lower bay have limited water movement. While the water from the large portion of Green Bay does find its way into Lake Michigan, the bay tends to have a hydrodynamic life of its own. When the water does exit, the outflow is carried south along the Wisconsin shore of Lake Michigan. During most of the year, the waters of the Fox River and several smaller rivers that empty into the west side of the bay are warmer than Lake Michigan, and therefore tend to remain on the surface. Colder water from Lake Michigan enters at depth through several channels at the north end of the bay. This two-layered system operates somewhat like a conveyor belt, with the warmer, nutrient-laden surface water moving northward, and the colder (generally cleaner) Lake Michigan water moving southward at the deeper layers.

• Residence Time --- The average residence time of Fox River water, and any dissolved pollution in the lower half of the bay, ranges from 100 to 160 days, depending on the rate of flow in the river.

LINKS TO MORE INFORMATION

Surf the Fox River Watershed --- EPA site loaded with information and links

Friends of the Fox River Trail --- This citizens organization formed recently to support the new pedestrian path along the abandoned railway on the east bank of the river, from the City of Green Bay to the City of DePere, then across farming country to Greenleaf.

Baird Creek Parkway Preservation Foundation --- Baird Creek is a tributary of the Fox River, largely within the City of Green Bay boundaries.  Many sections are heavily forested with old growth trees and other valuable recreational space and wildlife habitat.   The Foundation is working to preserve more sections to add to the Parkway for future public enjoyment.

Fox Communities Online --- A major directory of websites from our area

Gerard Bertrand, Jean Lang, John Ross. "The Green Bay Watershed - Past/Present/Future" Institute for Environmental Studies, UW-Madison, UW-Sea Grant College Program, Technical Report #229, January 1976.

Linda Weimer, et al, "Green Bay: Portrait of a Waterway." Collection of articles in the Green Bay Press Gazette, reproduced by UW-Sea Grant College Program, WIS-SG-79-130. 1979.

H.J. Harris, P.E. Sager, C.J. Yarbrough and H.J. Day, "Evolution of Water Resource Management: A Laurentian Great Lakes Case Study," International Journal of Environmental Studies, 1987, Vo. 29, pp. 053-070.

Peyton L. Smith, Robert A. Ragotzkie, Anders W. Andren, and Hallett J. Harris, "Estuary Rehabilitation: The Green Bay Story." Oceanus, 31(3):12-20, 1988.

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