Wisconsin’s Riverine and Lake Natural Communities

Protecting and preserving riverine and lake natural communities are important to the environment and economy of Wisconsin. New scientific findings have identified distinct "natural communities" into which different types of streams, rivers and lakes can be grouped. These groupings help us manage the resources more effectively.

Wisconsin's Riverine and Lake Natural Communities represent analyzed products from a USGS/DNR Bureau of Science Services model created based on predicted flow and temperatures. Ranges of flow and temperature for rivers are associated with specific aquatic life communities (fish, macroinvertebrates). Lake natural communities are based on lake surface area, stratification status, hydrology and watershed size, which are stored in the Register of Waterbodies (ROW) database. To find out more about how the communities were assigned read the natural community descriptions below and read about the stream model.

Physical and Biological Characteristics of Flowing Water Natural Communities (Rivers, Streams)

Macroinvertebrate

Very small, almost always intermittent (i.e., ceases flow for part of the year, although water may remain in the channel) streams. Few or no fish are present, but a variety of aquatic invertebrates are common, at least seasonally.

Ephemeral

Channels with water flow only after precipitation events (i.e., no base flow). No fish and few or no aquatic invertebrates are present. Note that streams with 90 percent exceedance flows of less than 0.03 CFS are considered macroinvertebrate streams if their watershed area is less than 1.5 square miles or if it is between 1.5 and 3.9 square miles with a gradient of more than 53 ft/mile.

Headwaters Category

Streams with flows less than 0.03 CFS but in larger watershed areas and lower gradients are put into the appropriate "headwaters" category.

Cold Headwater

Small, perennial streams with cold summer temperatures. Collectively, coldwater fishes are usually abundant (catch rate of >100 fish per 100 m of stream length sampled) to common (10–100 per 100 m), transitional fishes are common to absent and warm water fishes are absent. Because of the small size of the stream, trout populations consist almost exclusively of small fish (< 5 inches) with larger fish absent except perhaps during spawning periods.

Cold Mainstem

Moderate to large but still wadeable perennial streams with cold summer temperatures. Coldwater fishes are abundant to common, transitional fishes are common to absent and warm water fishes are absent. The size of the stream is sufficient to support trout in a wide range of sizes.

Cool (Cold–Transition) Headwater

Small, usually perennial streams with cold to cool summer temperatures. Coldwater fishes are common to uncommon (<10 per 100 m), transitional fishes are abundant to common and warm water fishes are uncommon to absent. Headwater species are abundant to common, mainstem species are common to absent and river species are absent.

Cool (Cold–Transition) Mainstem

Moderate to large but still wadeable perennial streams with cold to cool summer temperatures. Coldwater fishes are common to uncommon, transitional fishes are abundant to common and warm water fishes are uncommon to absent. Headwater species are common to absent, mainstem species are abundant to common and river species are common to absent.

Cool (Warm–Transition) Headwater

Small, sometimes intermittent streams with cool to warm summer temperatures. Coldwater fishes are uncommon to absent, transitional fishes are abundant to common and warm water fishes are common to uncommon. Headwater species are abundant to common, mainstem species are common to absent and river species are absent.

Cool (Warm–Transition) Mainstem

Moderate to large but still wadeable perennial streams with cool to warm summer temperatures. Coldwater fishes are uncommon to absent, transitional fishes are abundant to common and warm water fishes are common to uncommon. Headwater species are common to absent, mainstem species are abundant to common and river species are common to absent.

Warm Headwater

Small, usually intermittent streams with warm summer temperatures. Coldwater fishes are absent, transitional fishes are common to uncommon and warm water fishes are abundant to common. Headwater species are abundant to common, mainstem species are common to absent and river species are absent.

Warm Mainstem

Moderate to large but still wadeable perennial streams with relatively warm summer temperatures. Coldwater fishes are absent, transitional fishes are common to uncommon and warm water fishes are abundant to common. Headwater species are common to absent, mainstem species are abundant to common and river species are common to absent.

Warm Rivers

Non–wadeable large to very large rivers with warm summer temperatures. Coldwater fishes are absent, transitional fishes are common to uncommon and warm water fishes are abundant to common. Headwater species are absent, mainstem species are common to uncommon and river species are abundant to common.

Lake Natural Communities

Lake natural communities are based on lake surface area, stratification status, hydrology and watershed size, which are stored in the Register of Waterbodies (ROW) database. Natural Communities are predicted based on the guidelines described below.

Size

Lake classification begins by first splitting lakes into those 10-acres and greater and those less than 10 acres. Lakes less than 10 acres are classified into the small lake community. These lakes are uniquely different from communities in larger lakes but there is limited monitoring available. There are currently no condition thresholds set for water quality, fisheries, or aquatic plants for lakes less than 10 acres. Therefore, the 10-acre threshold reflects the limited availability of monitoring data with which to set thresholds for lake assessment.

Stratification status

If a lake is 10 acres or greater, it is further classified as either mixed or stratified. Lakes will be placed into the stratified category if they stratify throughout the summer or if they undergo intermittent stratification. Stratification is an important factor in determining the overall lake condition and availability of suitable habitat for fish and aquatic life. Stratification status is predicted by using a modified ratio of lake depth to lake surface area. Using data from ROW, this stratification equation, developed by DNR Integrated Science Services, distinguishes between clearly stratified and mixed lakes.

Hydrology and watershed size

The third measure to consider is the hydrology (seepage, headwater drainage and lowland drainage). A lake with no surface water inflow or outflow is considered a seepage lake. If there is surface water flow into and/or out of a lake from a river or stream then the lake is classified as a drainage lake. If the watershed draining to the lake is less than 4 square miles, the lake is classified as a headwater drainage lake. If the watershed draining to the lake is greater than or equal to 4 square miles, the lake is classified as a lowland drainage lake.

Attributes

About the Stream Model

The model used to generate proposed stream natural communities is based on a variety of base data layers at various scales, and was initially applied to the federal 100k scale NHD (National Hydrography Dataset) hydrography layer. The data was then extrapolated or "conflated" to the 24K scale DNR hydrography layer (version 5). Due to differences in scale, some streams in the DNR hydro layer were not assigned a predicted classification from the model (e.g. some streams at 24K scale do not appear at 100K scale).

Department scientists are in the process of re-running the model and updating predicted communities on a modified version of the DNR 24K hydrography layer (version 5) which should provide a more comprehensive array of natural communities for most Wisconsin Rivers and streams.

Proposed Natural Communities for Rivers and Streams in Wisconsin

Name, Waterbody ID Code (WBIC)

Lake name and Waterbody ID Code (WBIC). Note: WBICs created as part of version 6 hydro are not included in this dataset.

Natural Community

Clean Water Act Lake Natural Communities as predicted using lake data from the DNR ROW and 24K Hydrolayer databases. These are as follows:

Natural community	Stratification status	Hydrology
Lakes less than 10 acres
Small	Variable	Any hydrology
Lakes 10 acres or greater
Shallow seepage	Mixed	Seepage
Shallow headwater	Mixed	Headwater drainage
Shallow lowland	Mixed	Lowland drainage
Deep seepage	Stratified	Seepage
Deep headwater	Stratified	Headwater drainage
Deep lowland	Stratified	Lowland drainage
Other classifications (any size)
Spring ponds (a)	Variable	Spring hydrology
Two–story lakes (b)	Stratified	Any hydrology
Impounded flowing waters (c)	Variable	Headwater or lowland drainage
Based also on historically supporting a cold water fishery Based also on historically supporting a native cold water fishery >14 day residence time under summertime low flow conditions

Maximum depth, depth units, depth source, watershed area

Data associated with the WBIC above in the Register of Waterbodies (ROW) database.

Mix stratify ratio

The ratio, (MaxDepth–0.1)/(LOG(SurfaceArea)), is calculated using data from ROW. Units must be in meters for depth and hectares for surface area. Values greater than or equal to 3.90 are considered stratified while those less than 3.90 are considered mixed.

Lake hydrologic type

This is the “Water Source” code in ROW that has been populated from the DNR Lake Book [PDF]. For Water Source definitions see the Wisconsin Lake Book.

ROW waterbody type

This is the Waterbody Type field that has been populated from ROW. LP stands for lake or pond while RF denotes a reservoir or flowage. Waterbody type RF has some sort of water control structure at the outflow, while LP does not.

WATERS ID

Assessment Unit ID code from the WATERS database.

ROW ID

Waterbody ID code from the ROW database.