Rare animals
Find rare and non-game animals.
Rare plants
Learn about plants on the Natural Heritage Working List.
Rare lichens
Discover Wisconsin's lichens.
Natural communities
Explore Wisconsin's natural communities.
Other features
Discover unique resources.
Contact information
For information on Wisconsin's natural communities, contact:
Ryan O'Connor
Natural Heritage Inventory Ecologist

Riverine Impoundment - Reservoirs


General natural community overview

Impoundments (also known as reservoirs) are artificially created standing waterbodies, produced by dams on streams or rivers. Because of the diverse nature of streams, rivers, and dams, these waterbodies can vary greatly in size, configuration, flow patterns, water chemistry, and biota. Impoundments are nearly as numerous and diverse in characteristics as natural lakes, with larger and more southerly waters having the richest fish faunas. Most often the waterbodies are dominated by warmwater fishes, particularly the Centrarchidae family (sunfishes).

Rare animals

Species of Greatest Conservation Need

Wisconsin Wildlife Action Plan graphic

The following Species of Greatest Conservation Need are listed according to their level of association with the natural community type, based on the findings in Wisconsin's 2015 Wildlife Action Plan.

Scores: 3 = high association, 2 = moderate association, and 1 = low association. See the key to association scores for complete definitions.

Blanchard's Cricket FrogAcris blanchardi3
Mink FrogLithobates septentrionalis3
Pickerel FrogLithobates palustris2

Black TernChlidonias niger2
Forster's TernSterna forsteri2
Caspian TernHydroprogne caspia1
Common GoldeneyeBucephala clangula1
Common TernSterna hirundo1
Great EgretArdea alba1
Least BitternIxobrychus exilis1
Purple MartinProgne subis1
Yellow-crowned Night-HeronNyctanassa violacea1

Dragonflies and damselfliesScore
Pronghorn ClubtailGomphus graslinellus3
Slaty SkimmerLibellula incesta3
Double-striped BluetEnallagma basidens2
Lilypad ForktailIschnura kellicotti2
Mottled DarnerAeshna clepsydra2
Spangled SkimmerLibellula cyanea2
Unicorn ClubtailArigomphus villosipes2
Alkali BluetEnallagma clausum1
Painted SkimmerLibellula semifasciata1
Smoky RubyspotHetaerina titia1

Lake SturgeonAcipenser fulvescens3
Mud DarterEtheostoma asprigene3
Black BuffaloIctiobus niger2
GoldeyeHiodon alosoides2
PaddlefishPolyodon spathula2
Redfin ShinerLythrurus umbratilis2
American EelAnguilla rostrata1
Skipjack HerringAlosa chrysochloris1

Leafhoppers and true bugsScore
A Water StriderNeogerris hesione2

Big Brown BatEptesicus fuscus3
Little Brown BatMyotis lucifugus3
Silver-haired BatLasionycteris noctivagans2
Eastern PipistrellePerimyotis subflavus1
Northern Long-eared BatMyotis septentrionalis1
Water ShrewSorex palustris1

Mussels and clamsScore
Flat FloaterAnodonta suborbiculata2

Blanding's TurtleEmydoidea blandingii3
Plains GartersnakeThamnophis radix1

Please see Section 2. Approach and Methods of the Wildlife Action Plan to learn how this information was developed.

Rare plants

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

Scores: 3 = "significantly associated," 2 = "moderately associated," and 1 = "minimally associated."
Scientific Name Common Name Score
Callitriche hermaphroditica Autumnal Water-starwort 2
Callitriche heterophylla Large Water-starwort 2
Nuphar advena Yellow Water Lily 1
Nuphar microphylla Small Yellow Pond Lily 1
Potamogeton bicupulatus Snail-seed Pondweed 1
Potamogeton confervoides Algae-leaved Pondweed 1
Potamogeton diversifolius Water-thread Pondweed 2
Potamogeton oakesianus Oakes' Pondweed 1
Potamogeton pulcher Spotted Pondweed 1
Potamogeton vaseyi Vasey's Pondweed 2
Schoenoplectus torreyi Torrey's Bulrush 1
Utricularia resupinata Northeastern Bladderwort 1


The following Ecological Landscapes have the best opportunities to manage for , based on the Ecological Landscapes of Wisconsin Handbook.

Major (3 on map)
A major opportunity for sustaining the natural community in the Ecological Landscape exists, either because many significant occurrences of the natural community have been recorded in the landscape or major restoration activities are likely to be successful maintaining the community's composition, structure, and ecological function over a longer period of time.

Important (2 on map)
Although the natural community does not occur extensively or commonly in the Ecological Landscape, one to several occurrences do occur and are important in sustaining the community in the state. In some cases, important opportunities may exist because the natural community may be restricted to just one or a few Ecological Landscapes within the state and there may be a lack of opportunities elsewhere.

Present (1 on map)
The natural community occurs in the Ecological Landscape, but better management opportunities appear to exist in other parts of the state.


Wisconsin Wildlife Action Plan graphic

What are conservation actions?

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for natural communities




Northeast of New London, showing dikes and impoundments in floodplain, Outagamie County.

Photo by Eric Epstein.


Turtle-Flambeau Flowage, Iron County.

Photo by  staff.


Chippewa Flowage, Sawyer County.

Photo by  staff.


Aerial view of Lake Wisconsin, Columbia County.

Photo by Edward Smith.

Note: photos are provided to illustrate various examples of natural community types. A single photograph cannot represent the range of variability inherent in a given community type. Some of these photos explicitly illustrate unusual and distinctive community variants. The community photo galleries are a work in progress that we will expand and improve in the future.

Last revised: Wednesday, June 16, 2021