Lower Fox River TMDL
TMDL Development
Approved TMDL
Implement TMDL
Evaluate for Delisting

Project Description

The Lower Fox River (LFR) Basin is located in northeast Wisconsin. The LFR Basin and Lower Green Bay are impaired by excessive phosphorus and sediment loading, which leads to nuisance algae growth, oxygen depletion, reduced submerged aquatic vegetation, water clarity problems, and degraded habitat. The TMDL for the LFR Basin and Lower Green Bay focuses on waters impaired by excessive sediment and/or high phosphorus concentrations. Phosphorus and sediment cause numerous impairments to waterways, including low dissolved oxygen concentrations, degraded habitat, and excessive turbidity. These impairments adversely impact fish and aquatic life, water quality, recreation, and potentially navigation.

Over the last 15 years, the Wisconsin Department of Natural Resources (WDNR) has placed numerous waters in the LFR Basin, including Lower Green Bay, on the state�s 303(d) Impaired Waters List, and has ranked the waters as high priority for the development of TMDLs to address the impairments caused by excess phosphorus and sediment loading. The complete list of impaired waters and impairments being addressed by the TMDL are listed in Table 1 and shown in Figure 3. Note that the term �designated use� in Table 1 refers to those waters that are codified in Wisconsin Administrative Code NR 104.

There are 27 segments listed as impaired on the state�s 303(d) Impaired Waters List due to excess phosphorus and/or sediment loading, resulting in a need for 45 individual TMDLs. The TMDLs for the LFR Basin and Lower Green Bay were developed using a watershed framework to address each of the 45 TMDLs needed. Under a watershed framework, TMDLs and the associated tasks1 are simultaneously completed for multiple impaired water bodies in a watershed.

Project Goals

The following list summarizes the primary restoration goals for the LFR Basin (including tributary streams) and Lower Green Bay that will be addressed through implementation of this TMDL.

  • Reduce excess algal growth. Aesthetic reasons aside, reducing blue-green algae will reduce the risks associated with algal toxins to recreational users of the river and bay. In addition, a decrease in algal cover will also increase light penetration into deeper waters of the bay.

  • Increase water clarity in Lower Green Bay. Achieving an average Secchi2 depth measurement of at least 1.14 meters will allow photosynthesis to occur at deeper levels in the bay, as well as improve conditions for recreational activities such as swimming.

  • Increase growth of beneficial submerged aquatic vegetation in Lower Green Bay. This will help reduce the re-suspension of sediment particles from the bottom of the bay up into the water column, which will increase water clarity.

  • Increase dissolved oxygen levels. This will better support aquatic life in the tributary streams and main stem of the Lower Fox River.

  • Restore degraded habitat. This will better support aquatic life.

What's New

Updates to the TMDL implementation will be posted here as they are available.

Resource Conditions

Although phosphorus is an essential nutrient for plant growth, excess phosphorus is a concern for most aquatic ecosystems. Where human activities do not dominate the landscape, phosphorus is generally in short supply. The absence of phosphorus limits the growth of algae and aquatic plants. When a large amount of phosphorus enters a water body, it essentially fertilizes the aquatic system, allowing more plants and algae to grow; this leads to excessive aquatic plant growth, often referred to as an algae bloom. This condition of nutrient enrichment and high plant productivity is referred to as eutrophication. Eutrophication can damage the ecology of the water, degrade its aesthetics and swimming conditions, and affect the economic well-being of the surrounding community. Overabundant aquatic plant growth in a water body can lead to a number of undesirable consequences. Excessive surface vegetation blocks sunlight from penetrating the water, choking out beneficial submerged aquatic vegetation. Large areas of excessive surface vegetation growth can inhibit or prevent access to a waterway, which restricts use of the water for fishing, boating, and swimming. A bloom of aquatic plants may include toxic blue-green algae or cyanobacteria, which are harmful to fish and pose health risks to humans. Algal blooms, and particularly surface scums that form, are unsightly and can have unpleasant odors. This makes recreational use of the water body unpleasant and poses a problem for people who live close to the affected water body. When the large masses of both submerged and surface aquatic plants die, the decomposition of the organic matter depletes the supply of dissolved oxygen in the water, suffocating fish and other aquatic life; depending on the severity of the low dissolved oxygen event, large fish kills can occur. Nearly all of these effects have economic impacts on the local community, as well as the state.

The Lower Fox River, its tributaries, and Lower Green Bay are also impacted by excess sediment loading. Excess sediments in the river and bay scatter and absorb sunlight, reducing the amount of light that reaches submerged aquatic vegetation, which restricts its ability to grow via photosynthesis. Bottom-rooted aquatic plants produce life-giving oxygen, provide food and habitat for fish and other aquatic life, stabilize bottom sediments, protect shorelines from erosion, and utilize nutrients that would otherwise be available for nuisance algae growth. As photosynthetic rates decrease, less oxygen is released into the water by the plants. If light is completely blocked from bottom dwelling plants, the plants stop producing oxygen and die. While decomposing the plants, bacteria use up even more oxygen from the water. Historically, fish kills have been reported in Green Bay and the Lower Fox River in association with low oxygen events (WDNR, 1988; WDNR, 1993a).

Submerged aquatic vegetation also serves as vital habitat and is a food source for fish, waterfowl, frogs, turtles, insects, and other aquatic life. Reduced water clarity also interferes with the ability of fish and waterfowl to see and catch food. Suspended sediments can also clog fish and invertebrate gills and cause respiratory stress. When sediments settle to the bottom of the river and bay, they can smother the eggs of fish and aquatic insects, as well as suffocate newly hatched insect larvae. Settling sediments can also fill in spaces between rocks, reducing the amount of sheltered habitat available to aquatic organisms. The aforementioned ability of sediment particles to absorb heat from sunlight can also cause an increase in surface water temperature. This can cause dissolved oxygen levels to drop even lower (warmer waters hold less dissolved oxygen that colder waters), and further harm aquatic life.

Interactive Viewer

  • Restoration Viewer This interactive webmapping application displays mapping products specifically for TMDL implementation.
  • Surface Water Data Viewer The Surface Water Data Viewer is a generalized interactive mapping application that displays a wide variety of water related datasets.
  • Water Condition Viewer The Water Condition Viewer provides monitoring, assessments, and management datasets for water quality.

GIS Maps

GIS map of the TMDL sites in Wisconsin
Wisconsin's Total Maximum Daily Loads

About TMDLs

South Fork Eau Claire River, Lisa HelmuthWisconsin's TMDL Program is working on a variety of flyers and handouts to support a common understanding of the state's TMDL process and requirements. Overview of TMDLs [TMDL Page]

What is a TMDL [PDF]
A Total Maximum Daily Load (TMDL) is the maximum amount of a pollutant that a body of water can receive while still meeting water quality standards. A waterway that exceeds standards is often no longer suitable for its designated uses, such as wildlife habitat, fishing, or other recreational activities.

Frequently Asked Questions (FAQs)[PDF]
"Why do we need to create TMDLs?", "What is an "impaired water"?", and "How is a TMDL implemented?"


DNR Water Webinars [Go to Webinar Page]

Trading and Adaptive Management
UW Extension Webinars on Adaptive Mangement [exit DNR]

Water Quality Trading & Adaptive Management
The Basics || PDF Format
Finding, Quantifying Credits || PDF Format
Developing a Plan || PDF Format
Implementing and Verifying Offsets || PDF Format

Understanding Phosphorus Rules & Management Options
Adaptive Management Basics [3/3/12]
Phosphorus Discharge Limits [3/3/12]
Complying with Phosphorus Discharge Limits [3/28/12]
Water Quality Trading Framework Update [2/10/11]

Clean Water Act: Water Quality Report to Congress
Impaired Waters List Updates, 2014
Water Quality Report to Congress Webinar 2012
Water Quality Report to Congress: Impaired Waters & Water Quality Planning [12/05/11]
Water Quality Management Planning July 2010-11 [07/13/10]
Water Quailty Report to Congress & Website Overview [12/09]