Wis. Admin. Code Department of Natural Resources NR 102.56
This section contains numeric biological assessment thresholds for evaluating the biological condition of lakes, reservoirs, and impounded flowing waters and determining whether applicable designated uses are being attained. Numeric biological assessment thresholds used to assess attainment of designated uses include all of the following:
Note: The aquatic life chlorophyll a thresholds do not apply to streams, rivers, or impounded flowing waters, as they were established based on lake trophic status levels.
Table 8
Aquatic plant community thresholds for lakes and reservoirs
Lake subcategory1 | Macrophyte assessment of condition is attained if: |
Northern seepage | Moderately tolerant [LESS THAN OR EQUAL] 64% |
Northern drainage | Tolerant [LESS THAN OR EQUAL] 73% |
Southern seepage | Sensitive [GREATER THAN] 15% |
Southern drainage | Tolerant [LESS THAN OR EQUAL] 50% |
1 In Table 8, northern lakes are those north of 44.84707° N latitude, and southern lakes are those south of that latitude. These thresholds do not apply to the Great Lakes or lakes less than 5 acres in surface area.
Note: Examples of department-approved sampling protocols include the "Recommended Baseline Monitoring of Aquatic Plants in Wisconsin," available on the department's website in the Electronic Guidance and Documents (EGAD) system at https://dnr.wi.gov/water/egadsearch.aspx. Examples of department-approved analysis protocols include the "Macrophyte Assessment of Condition - General" (MAC-Gen) for general condition assessments applicable to this section, and the "Macrophyte Assessment of Condition - Phosphorus" (MAC-P) for phosphorus-specific assessments under s. NR 102.60 (2) (c). Each MAC protocol contains the tolerance groups assigned to each species. MAC-Gen and MAC-P scores can be obtained by contacting the department at DNRSWIMS@wisconsin.gov and submitting aquatic plant data collected and formatted according to department specifications. Computer programming script written in the R language to compute the MAC calculations can be obtained through the department's Water Evaluation Section by contacting the department's call center at 1-888-WDNRINFo (1-888-936-7463) or using options provided on its website at https://dnr.wi.gov/contact/.
Table 9
Algae thresholds for recreational use assessments
Waterbody type1 | Subcategory | Thresholds for frequency of moderate algae levels |
Lakes, reservoirs, impounded flowing waters (includes cold and warm) | Impounded flowing water, unstratified drainage, unstratified seepage | Does not exceed 20 ug/L chlorophyll a for more than 30% of days during the summer sampling period2 |
Stratified drainage, stratified seepage | Does not exceed 20 ug/L chlorophyll a for more than 5% of days during the summer sampling period2 | |
Stratified two- story fishery |
1 Terms used for waterbody types and subcategories are defined in s. NR 102.03.
2 Summer sampling period is July 15 to September 15.
Note: Lakes and reservoirs are subcategorized based on both their stratification status (stratified vs. unstratified) and whether or not they have an outlet stream or river (drainage vs. seepage). To find a lake or reservoir's subcategory, also known as its natural community, go to the department's Surface Water Data Viewer online map at https://dnr.wi.gov/topic/surfacewater/swdv/ and turn on the layer for Surface Water: Lake Natural Communities. On the natural communities layer, unstratified is referred to as "shallow," and stratified is referred to as "deep." Headwater and lowland lakes are types of drainage lakes.
Note: The U.S. EPA has set human health swimming advisory levels for microcystin and cylindrospermopsin that accurately reflect the latest scientific information on the potential human health effects from recreational exposure to these two cyanotoxins. The department recommends that local and tribal public health agencies use these swimming advisory levels for notification purposes in recreational waters to protect the public. More information can be found at https://dnr.wisconsin.gov/topic/lakes/bluegreenalgae.
Wis. Admin. Code Department of Natural Resources NR 102.56
The statistical calculation for determining the frequency of moderate algae levels is contained in Wisconsin's Consolidated Assessment and Listing Methodology (WisCALM) guidance document.