Overview

Horicon Marsh consists of both the Horicon National Wildlife Refuge (HNWR), is primarily administered by the U.S. Fish and Wildlife Service and the Horicon Marsh Wildlife Area (HMWA) which is administered by the Wisconsin WDNR. The HNWR covers 20,976 acres in the northern 2/3 of the marsh and the HMWA covers 10,928 acres in the southern 1/3 of the marsh for a combined total of 31,904 acres. The size of the marsh makes it one of the largest freshwater wetlands in the United States. There are 216 species of birds which use Horicon Marsh as well as 32 other bird species which have been reported in the marsh (USFWS, 1994). There is also a wide variety of fish, aquatic animals and mammals which utilize the marsh. Due to the extremely large size of the marsh, as well as other factors such as the diversity of flora and fauna and the large populations of waterfowl it supports, Horicon Marsh has been designated as a "Wetland of International Importance". This recognition affirms the high natural resource value of Horicon Marsh not only for Wisconsin, but nationally and internationally as well.

Horicon Marsh is located entirely within the boundaries of the Upper Rock River Watershed (UR12). The primary water source to the state portion of the marsh is the East Branch Rock River which originates in the East Branch Rock River Watershed (UR13), located directly east of the marsh. Sources of water to the Federal portion marsh are the West and South Branches of the Rock River which are contained in the Upper Rock River watershed (UR12). The primary land use in both watersheds is intensive agriculture. There are three smaller-sized municipalities in the immediate vicinity of the marsh; Horicon, Mayville and Waupun. There are also numerous smaller communities in the area surrounding the marsh.

Horicon Marsh is used by the public for a wide variety of outdoor activities. Wisconsin WDNR records show that the most popular activities on the marsh are waterfowl marsh observation, canoeing, duck hunting, goose hunting, deer hunting (gun & bow), fishing, snowmobiling, hiking and dog training and dog trials. These activities combined represent approximately 106,000 visitor days of use of the marsh on the state portion alone. These figures illustrate both the economic and cultural importance of Horicon Marsh.

Despite the fact that Horicon Marsh has been recognized as a Wetland of International Importance, several severe problems continue to threaten many of the important resources of the marsh. The most severe problem is siltation due to soil erosion from the surrounding watersheds. Other major problems in the marsh are rough fish infestation (mainly carp), purple loosestrife infestation, high inflow of nutrients into the marsh from surrounding farms, pastures and barnyards and the loss of wildlife habitat.

Siltation is the most severe water quality problem affecting Horicon as determined by the water quality monitoring conducted by the Rock River Partnership in 1998 and 1999. Previous department documents have stated that heavy silt loads, particularly from the East Branch Rock River, contribute to the marsh becoming much shallower in many of its bays and channels. The largest source of sediment to the marsh is soil erosion from agricultural lands. Farming practices such as wetland drainage, fall plowing, farming too close to streambanks, farming on steep slopes and livestock grazing on streambanks all contribute to the marsh's siltation problems. Fish and wildlife habitat use and recreational use are greatly affected by this problem (USFWS, 1994).

Date  2002

Author   Aquatic Biologist

Overview

A severe overabundance of carp in the marsh has contributed to decreased water quality. Carp are able to tolerate poorer water quality conditions than more desirable fish. The feeding habits of carp muddy the water, uproot vegetation and compete with more valuable fish and wildlife species for invertebrate food organisms. The poor water quality and shallowness of the marsh due to erosion makes it difficult to control the carp problem and maintain a gamefish population. The carp and soil erosion problems are directly linked and the problems with carp will continue as long as the heavy siltation of the marsh continues. In the winter of 1999, a drawdown of the marsh was conducted. Chemical poisoning of the carp population was completed. The marsh was refilled in the spring of 2000.

The high inflow of nutrients, phosphorus and nitrogen, into Horicon Marsh from surrounding farm fields where manure and other fertilizer is spread, as well as runoff from barnyards and feedlots, is also a serious problem. The high phosphorus levels fuel cattail bog expansion, closing off prime wildlife habitats. The nutrients from these sources results in excessive algae and aquatic plant growth which can lead to serious dissolved oxygen problems and may cause fishkills, especially in the winter months. Past water quality monitoring in the marsh has detected levels of pesticides and inorganic fertilizers in the marsh. The effects of these substances on the marsh ecosystem are unknown at this time.

It is clear that land use practices around Horicon Marsh are slowly degrading the quality of this valuable natural resource. Nonpoint source pollution, especially, needs to be addressed in a comprehensive and holistic manner if the problems of the marsh are going to be resolved. One of the most important projects undertaken is the gathering of quantifiable data on sediment and phosphorus loadings to the marsh from streams in the Upper Rock River Watershed and from the East Branch Rock River Watershed.

The state portion of the marsh is more affected by water quality problems than the federal portion because the state portion is primarily a single impoundment. However, a new impoundment in the state acreage, the Bachhuber Flowage, became an operational in 2001. The federal portion of the marsh is a series of impoundments. This allows for better management in the federal portion because of the multiple-impoundments (Volkert, 199431).

A positive note is the formation of a local group to address the problems, threats and opportunities for Horicon Marsh. This group, the Horicon Marsh Area Coalition, is comprised of representatives from local conservation groups, local property owners and local, state and federal agencies. Another group, the Rock River Headwaters, Inc. has been formed to investigate ways of linking together divergent community projects for recreation, resource protection and historical tourism.

Date  2002

Author   Aquatic Biologist

Overview

For more detailed descriptions of the history, management and resources of the Horicon Marsh, see the "Horicon Marsh Wildlife Area Master Plan Concept Element" (WDNR, 1983) or "Horicon Marsh, Wisconsin, A Wetland of International Importance" (WDNR, 1992).

Date  2002

Author   Aquatic Biologist

Overview

HORICON MARSH MANAGEMENT RECOMMENDATIONS
1. The nonpoint source priority watershed selection committee should consider designating both the Upper Rock River (UR12) and East Branch Rock River UR13) watersheds as priority for TRM and Urban Nonpoint Source Grants under the Nonpoint Source Water Pollution Abatement Program, to protect Horicon Marsh from further degradation (both watersheds have tributaries to Horicon Marsh).

2. Watershed Management (WM) staff, in cooperation with the U.S. Fish and Wildlife Service, should identify strategies to acquire or otherwise protect critical wetlands and other environmentally sensitive areas surrounding Horicon Marsh.

3. WM staff should work with Dodge, Fond Du Lac and Washington counties to more aggressively educate citizens about and enforce existing shoreland/wetland protection zoning ordinances.

4. WM staff, with the assistance of Wildlife Management and Dodge, Fond Du Lac and Washington County land Conservation Departments, should continually monitor and better document sediment and phosphorous loading to Horicon Marsh from the Upper Rock River Watershed (UR12) and the East Branch Rock River Watershed (UR13) from smaller subwatersheds.

5. WM staff should continue monitoring Horicon Marsh water quality.

Date  2002

Author   Aquatic Biologist

Condition

Wisconsin has over 84,000 miles of streams, 15,000 lakes and milllions of acres of wetlands. Assessing the condition of this vast amount of water is challenging. The state's water monitoring program uses a media-based, cross-program approach to analyze water condition. An updated monitoring strategy (2015-2020) is now available. Compliance with Clean Water Act fishable, swimmable standards are located in the Executive Summary of Water Condition in 2018. See also the 'monitoring and projects' tab.

Reports

Management Goals

Wisconsin's Water Quality Standards provide qualitative and quantitative goals for waters that are protective of Fishable, Swimmable conditions [Learn more]. Waters that do not meet water quality standards are considered impaired and restoration actions are planned and carried out until the water is once again fishable and swimmable

Management goals can include creation or implementation of a Total Maximum Daily Load analysis, a Nine Key Element Plan, or other restoration work, education and outreach and more. If specific recommendations exist for this water, they will be displayed below online.

Monitoring

Monitoring the condition of a river, stream, or lake includes gathering physical, chemical, biological, and habitat data. Comprehensive studies often gather all these parameters in great detail, while lighter assessment events will involve sampling physical, chemical and biological data such as macroinvertebrates. Aquatic macroinvertebrates and fish communities integrate watershed or catchment condition, providing great insight into overall ecosystem health. Chemical and habitat parameters tell researchers more about human induced problems including contaminated runoff, point source dischargers, or habitat issues that foster or limit the potential of aquatic communities to thrive in a given area. Wisconsin's Water Monitoring Strategy was recenty updated.

Grants and Management Projects

Monitoring Projects

Watershed Characteristics

Horicon Marsh is located in the Upper Rock River watershed which is 257.61 mi². Land use in the watershed is primarily agricultural (54.60%), wetland (24.60%) and a mix of grassland (11.90%) and other uses (8.80%). This watershed has 335.43 stream miles, 1,629.48 lake acres and 40,442.61 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked Medium for runoff impacts on streams, High for runoff impacts on lakes and High for runoff impacts on groundwater and therefore has an overall rank of High. This value can be used in ranking the watershed or individual waterbodies for grant funding under state and county programs.This water is ranked High Lake for individual Wetlandss based on runoff problems and the likelihood of success from project implementation.