St. Croix Flowage, Upper St. Croix and Eau Claire Rivers Watershed (SC18)
St. Croix Flowage, Upper St. Croix and Eau Claire Rivers Watershed (SC18)
St. Croix Flowage (2740300)
2247.38 Acres
Natural Community
Natural communities (stream and lake natural communities) represent model results that use predicted flow and temperature based on landscape features and related assumptions. Ranges of flow and temperature associated with specific aquatic life communities (fish, macroinvertebrates) help biologists identify appropriate resource management goals. Wisconsin Natural Communities.
Year Last Monitored
This is the most recent date of monitoring data stored in SWIMS. Additional surveys for fish and habitat may be available subsequent to this date.
This is impaired
Mercury Contaminated Fish Tissue
Trout Water 
Trout Waters are represented by Class I, Class II or Class III waters. These classes have specific ecological characteristics and management actions associated with them. For more information regarding Trout Classifications, see the Fisheries Trout Class Webpages.
Outstanding or Exceptional 
Wisconsin has designated many of the state's highest quality waters as Outstanding Resource Waters (ORWs) or Exceptional Resource Waters (ERWs). Waters designated as ORW or ERW are surface waters which provide outstanding recreational opportunities, support valuable fisheries and wildlife habitat, have good water quality, and are not significantly impacted by human activities. ORW and ERW status identifies waters that the State of Wisconsin has determined warrant additional protection from the effects of pollution. These designations are intended to meet federal Clean Water Act obligations requiring Wisconsin to adopt an 'antidegradation' policy that is designed to prevent any lowering of water quality - especially in those waters having significant ecological or cultural value.
Impaired Water 
A water is polluted or 'impaired' if it does not support full use by humans, wildlife, fish and other aquatic life and it is shown that one or more of the pollutant criteria are not met.

Fish and Aquatic Life

Current Use
The use the water currently supports. This is not a designation or classification; it is based on the current condition of the water. Information in this column is not designed for, and should not be used for, regulatory purposes.
Shallow Lowland
Shallow lowland lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.
Attainable Use
The use that the investigator believes the water could achieve through managing "controllable" sources. Beaver dams, hydroelectric dams, low gradient streams, and naturally occurring low flows are generally not considered controllable. The attainable use may be the same as the current use or it may be higher.
Aquatic Life
Waters that support fish and aquatic life communities (healthy biological communities).
Designated Use
This is the water classification legally recognized by NR102 and NR104, Wis. Adm. Code. The classification determines water quality criteria and effluent limits. Waters obtain designated uses through classification procedures.
Streams capable of supporting a cold water sport fishery, or serving as a spawning area for salmonids and other cold water fish species. Representative aquatic life communities, associated with these waters, generally require cold temperatures and concentrations of dissolved oxygen that remain above 6 mg/L. Since these waters are capable of supporting natural reproduction, a minimum dissolved oxygen concentration of 7 mg/L is required during times of active spawning and support of early life stages of newly-hatched fish.


St. Croix Flowage, in the Upper St. Croix and Eau Claire Rivers Watershed, is a 2,247.33 acre impoundment that falls in Douglas County. This impoundment is an outstanding/exceptional resource water under NR102 under the Fisheries Program. This impoundment is managed for fishing and swimming and is currently considered impaired.

Date  2011

Author   Aquatic Biologist

Historical Description

This 1913 acre impoundment was created by the construction of a twelve-foot head dam across
the St. Croix River as a WPA project in 1936. The sometimes called "Gordon Howage" is
shallow (mean depth - 6.5 ft.) and contains an abundance of aquatic vegetation and has over a
thousand acres of adjoining wetlands. The flowage has an excellent fishery and is an
outstanding waterfowl and furbearer producer. Migratory waterfowl also use the flowage as a
staging area in the spring and fall.

The shoreline community around the flowage has recently formed a lake association and
requested WRM assistance in dealing with the overabundance of aquatic vegetation which is
causing use problems. A feasibility study to document current vegetation patterns, densities and
any possible causes would be a desireable step for this waterbody.

Date  1992

Author   Surface Water Inventory Of Wisconsin

St. Croix Flowage, Upper St. Croix and Eau Claire Rivers Watershed (SC18) Fish and Aquatic LifeSt. Croix Flowage, Upper St. Croix and Eau Claire Rivers Watershed (SC18) RecreationSt. Croix Flowage, Upper St. Croix and Eau Claire Rivers Watershed (SC18) Fish Consumption

Impaired Waters

St. Croix Flowage (2740300) was placed on the impaired waters list for Mercury in fish tissue in 1998. This water was assessed during the 2016 listing cycle; total phosphorus and chlorophyll sample data were clearly below 2016 WisCALM listing thresholds for the Recreation use and Fish and Aquatic Life use. This lake is considered impaired for Fish Consumption use and meeting REC and FAL uses.

Date  2015

Author  Aaron Larson


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.



Land Acquisition
Douglas County will acquire approximately 128 acres (six parcels) of land located on the Gordon/St. Croix Flowage to protect the headwaters of the St. Croix Scenic Riverway. The properties include primarily wooded acreage located along both the southern shore of the flowage and Wilcox Island along the northern shore. The property will be managed by the County Forestry Department as either special use areas to preserve and protect the water quality and wildlife habitat of the flowage or as county forest lands. The primary goals - preserve and protect the water quality of the flowage and the high quality fishery and wildlife habitat, rich in both aquatic and terrestial bio-diversity -- protect the southern shoreline of the flowage from further development, and 3) to protect and maintain as a unique benchmark stand the old growth red and white pine stand on Wilcox Island. -

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 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

St Croix Flowage is located in the Upper St. Croix and Eau Claire Rivers watershed which is 277.89 miĀ². Land use in the watershed is primarily forest (83.90%), wetland (9.50%) and a mix of open (4.30%) and other uses (2.40%). This watershed has 153.93 stream miles, 7,654.41 lake acres and 13,694.48 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked Not Ranked for runoff impacts on streams, Not Ranked for runoff impacts on lakes and Low for runoff impacts on groundwater and therefore has an overall rank of Low. This value can be used in ranking the watershed or individual waterbodies for grant funding under state and county programs.However, all waters are affected by diffuse pollutant sources regardless of initial water quality. Applications for specific runoff projects under state or county grant programs may be pursued. For more information, go to surface water program grants.

Natural Community

St. Croix Flowage is considered a Reservoir under the state's Natural Community Determinations.

Natural communities (stream and lake natural communities) represent model results and DNR staff valiation processes that confirm or update predicted conditions based on flow and temperature modeling from historic and current landscape features and related variables. Predicated flow and temperatures for waters are associated predicated fish assemblages (communities). Biologists evaluate the model results against current survey data to determine if the modeled results are corect and whether biological indicators show water quaity degradation. This analysis is a core component of the state's resource management framework. Wisconsin's Riverine Natural Communities.

Maps of Watershed