Note: Waterbodies described in subd. 5 are also known as altered warmwater or altered macroinvertebrate waters.
6. A waterbody designated by the department as limited forage fish shall attain a minimum dissolved oxygen concentration of 3 mg/L at all times.
7. A waterbody designated by the department as limited aquatic life or wetlands, or classified as diffuse surface waters or wastewater effluent channels shall attain a minimum dissolved oxygen concentration of 1 mg/L at all times when water is present.
Section 4 NR 102.04 (4) (am) is created to read:
NR 102.04 (4) (am) Oxythermal layer thickness for two-story fishery lakes. 1. ‘Criteria.’ A two-story fishery lake shall maintain, during its period of summer stratification, an oxythermal layer of at least 1 meter in thickness that maintains both a dissolved oxygen concentration of at least 6 mg/L and a maximum temperature of the following:
a. For a two-story fishery lake with lake trout, 57° F or less.
b. For a two-story fishery lake with whitefish but not lake trout, 66° F or less.
c. For a two-story fishery lake with cisco but not whitefish or lake trout, or that the department manages for brook, brown, or rainbow trout, 73°F or less.
d. For a two-story fishery lake with multiple coldwater fish species, the applicable criterion under subd. 1. a. to c. is that for the lake’s species requiring the lowest temperature.
2. ‘Assessment.’ a. The monitoring period for the criteria under subd. 1. is June 1 to September 15. When monitoring for assessment purposes, depth profiles of temperature and dissolved oxygen shall, whenever possible, be taken in increments of 1 meter or less near the deepest part of the lake, at least monthly July to September. Samples taken outside this time frame but during summer stratification may also be used to determine assessment.
Note: Reservoirs, multi-lobed lakes, or very large lakes may need more than one sampling station to assess the lake.
b. If at any time during a lake’s summer stratification the applicable criterion in subd. 1. is not met, that year is an exceedance year. At least 2 years of data are needed to make an impairmentattainment determination. If any 2 or more years within the most recent 5-year period are exceedance years, the lake is not attaining the water quality criterion and shall be listed on the section 303 (d) list. If insufficient data are available from the most recent 5-year period, data from up to 10 years may be used if representative of current conditions.
Section 5 NR 102.04 (4) (b) is repealed.
Section 6 NR 102.04 (4) (d) is amended to read:
NR 102.04 (4) (d) OtherToxic substances. Unauthorized concentrations of substances are not permitted that alone or in combination with other materials present are toxic to fish or other aquatic life. Surface waters shall meet the acute and chronic criteria as set forth in or developed pursuant to ss. NR 105.05 and 105.06. Surface waters shall meet the criteria which correspond to the appropriate fish and aquatic life subcategory for the surface water, except as provided in s. NR 104.02 (3). Section 7 NR 102.04 (4) (f) and (Note) and (g) areis created to read:
NR 102.04 (4) (f) Chlorophyll a. 1. ‘Criteria.’ a. Mean suspended chlorophyll a concentrations in lakes and reservoirs other than stratified two-story fishery lakes shall not exceed 27 ug/L.
b. Mean suspended chlorophyll a concentrations in stratified two-story fishery lakes shall not exceed 8 ug/L.
2. ‘Assessment.’ Data requirements are the same as those specified in s. NR 102.07 (1) (a) 1., except that the sampling period for chlorophyll a is July 15 to September 15. To determine attainment of the chlorophyll a criterion under subd. 1., the department shall compare the waterbody’s mean suspended chlorophyll a concentration during the sampling period to the criterion, using the confidence interval approach described under s. NR 102.52 (2) (b) to (c) to determine if additional samples are needed. Note: The aquatic life chlorophyll a criteria do not apply to streams, rivers, or impounded flowing waters, as they were established based on lake trophic status levels.
(g)NR 102.04 (4) (f) Other criteria. Surface waters shall meet all other criteria that correspond to the appropriate aquatic life subcategory for the surface water, including narrative criteria specified in sub. (1) and biocriteria described in subch. III.
Section 8 NR 102.04 (5) (b) is amended to read:
NR 102.04 (5) (b) Exceptions. Whenever the department determines, in accordance with the procedures specified in s. NR 210.06 (3), that wastewater disinfection is not required to protect recreational uses, the criteria specified in par. (a)sub. (6) (a) and in chs. NR 103 and 104 do not apply. Section 9. NR 102.04 (6) (b), Table B, (Note 1), and (Note 2) are created to read:
[Note to LRB: NR 102.04 (6) (a) and Table A are created in Board Order WY-17-15.]
NR 102.04 (6) (b) Frequency of moderate algae levels. 1. ‘Criteria.’ A moderate algae level is defined as a chlorophyll a concentration of 20 ug/L or greater. Lakes, reservoirs, and impounded flowing waters shall not exceed the frequency of moderate algae levels specified in Table B during the summer sampling period.
Table B
Recreational use criteria for frequency of moderate algae levels
Waterbody Type1 | Subcategory | Criteria 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 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.wi.gov/lakes/bluegreenalgae/Default.aspx. 2. ‘Assessment.’ Data requirements are the same as those specified in s. NR 102.07 (2) (a) 1., except that the sampling period for chlorophyll a in all waterbody types is July 15 to September 15. To determine attainment of the criterion, the department shall statistically determine a waterbody’s frequency of moderate algae levels during the chlorophyll a summer sampling period using the confidence interval approach as described under s. NR 102.52 (2) (b) and (c) and compare that frequency to the applicable criterion in Table B. Section 910. NR 102.06 (1) and (2) (intro.) areis amended to read:
NR 102.06 (1) General. This section identifies the water quality criteria for total phosphorus that shall be met in surface waters. Assessment procedures for waterbodies are specified in s.ss. NR 102.07 and 102.60. Section 11. NR 102.06 (2) (intro.) is amended to read:
NR 102.06 (2) Definitions. In this section, the following definitions apply:
Section 1012. NR 102.06 (2) (a), (f), and (fm), and (j) are renumbered 102.03 (1o), (4m)(4s) and (6h)., (6e), and (7m).
[Note to LRB: A separate rule package, WY-23-19, creates a definition for NR 102.03 (4e) and (4m), which affects the numbering of definition (4s) renumbered under this Section.]
Section 1113. NR 102.06 (2) (g) and (2) (i) are renumbered 102.03 (6p)(6m) and (6t)(6s) and amended to read:
NR 102.03 (6p)(6m) “Stratified lake or reservoir” means a lake or reservoir where either of sufficient field data demonstrate that the lake is dimictic or, in absence of sufficient field data, the following equationsequation results in a value of greater than 3.8:
Maximum Depth (meters) — 0.1
Log10Lake Area (hectares)
Maximum Depth (feet)* 0.305 — 0.1
Log10Lake Area (acres) * 0.405
(6t)(6s) “Stratified two-story fishery lake” means a stratified lake which has supported a cold water fishery in its lower depths within the last 50 yearsor “two-story fishery lake” means a lake greater than 5 acres in size that is typically stratified in the summer, with the potential for an oxygenated hypolimnion, that has documentation since 1975 of a population of cold water fish species such as cisco, whitefish, or trout that is sustained through natural reproduction or long-term active stocking with year-to-year survival.
Section 1214. NR 102.03 (6t)(6s) (Note) is created to read:
NR 102.03 (6t)(6s) Note: A list of two-story fishery lakes that contain naturally reproducing lake trout, whitefish, or cisco, or are stocked and managed by the department for brook, brown, rainbow, or lake trout, is available on the department’s designated uses website at https://dnr.wi.gov/topic/SurfaceWater/usedesignations.html. Section 1315. NR 102.06 (3) (title) is repealed and recreated to read:
NR 102.06 (3) (title) Rivers, streams, and impounded flowing waters.
Section 1416. NR 102.06 (4) (c) is renumbered 102.06 (3) (c) and amended to read:
NR 102.06 (3) (c) Waters impounded on rivers or streams that don’t meet the definition of reservoir in this sectionAn impounded flowing water shall meet the river andor stream criterion in sub. (3)par. (a) or (b) that applies to the primary stream or river entering the impounded water.
Section 1517. NR 102.06 (7) (Note 2) is repealed. [Note that Board Order WY-09-18 renumbers (7) to (7) (a).]
Section 1618. NR 102.07 is created to read:
NR 102.07 Phosphorus assessment procedures. (1) Definitions. In this section, the following definitions apply:
(b) “Weather-controlled total phosphorus concentration” means a waterbody’s mean or median total phosphorus concentration during the applicable assessment period, estimated from measured data while controlling for weather variability using a method such as the department’s Phosphorus Mixed Effects Regression calculation method.
Note: A mean concentration is used for lakes or reservoirs; a median concentration is used for streams, rivers, or impounded flowing waters. Total phosphorus data may be submitted and weather-controlled concentrations can be obtained by contacting the department at DNRSWIMS@wisconsin.gov for access to the department’s SWIMS database. The statistical computer programming script to run the Phosphorus Mixed Effects Regression calculation 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/. NR 102.07 Assessing phosphorus concentration. (1) Data requirements. (a) Lakes and reservoirs.(2) General assessment procedure. (a) Data requirements. 1. ‘Lakes and reservoirs.’ The total phosphorus criteria specified in s. NR 102.06 (4) apply to samples taken near a lake or reservoir’s deepest point, within 2 meters of the surface. For assessment purposes samples shall, whenever possible, be taken at least once per month for 3 months during the sampling period of June 1 to September 15. When calculatingThe department shall calculate a lake or reservoir’s mean total phosphorus concentration, the department shall use using at least 2 years of data from the sampling period. Note: Reservoirs, multi-lobed lakes, or very large lakes may need more than one sampling station to assess the lake.
2. ‘Flowing waters.’(b) Flowing waters. The total phosphorus criteria specified in s. NR 102.06 (3) apply to samples taken from the main channel near the area with greatest flow. For assessment purposes samples shall, whenever possible, be taken at least once per month for 6 months during the sampling period of May 1 to October 31. When calculatingThe department shall calculate the median total phosphorus concentration for a stream, river, or impounded flowing water, the department shall use using at least one year of data from the sampling period. 3. ‘Assessment timeframe for lakes, reservoirs and flowing waters.’(c) Assessment timeframe for lakes, reservoirs and flowing waters. 1. In this paragraph, “wWeather-controlled total phosphorus concentration” means a waterbody’s mean or median total phosphorus concentration during the applicable assessment period, estimated from measured data while controlling for weather variability using a method such as the department’s Phosphorus Mixed Effects Regression calculation method.
2. All representative data from the most recent 5 years shall be used for assessments, but data from the most recent 10 years may be used if representative of current conditions. If fewer than the recommended number of samples in subd. 1. or 2.par. (a) or (b) are available, the department may be able to make an assessment determination on a case-by-case basis. The department may calculate a site’s weather-controlled total phosphorus concentration, defined in s. NR 102.07 (1) (b), to correct for weather variability and use this value to make an assessment determination in place of the mean or median calculated under subd. 1. or 2.par. (a) or (b). Note: A mean total phosphorus concentration is used for lakes or reservoirs; a median concentration is used for streams, rivers, or impounded flowing waters. Total phosphorus data may be submitted and weather-controlled concentrations can be obtained by contacting the department at DNRSWIMS@wisconsin.gov for access to the department’s SWIMS database. The statistical computer programming script to run the Phosphorus Mixed Effects Regression calculation 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/. Note: The procedures in subd. 2 is pars. (b) to (c) are also used for determining upstream concentrations of phosphorus under s. NR 217.13 (2) (d) for purposes of calculating a water-quality based effluent limit for a Wisconsin pollutant discharge elimination system (WPDES) permit. (b) Exceedance determination.(2) Exceedance determination. The department shall compare the mean or median calculated under par. (a)sub. (1) to the waterbody’s applicable total phosphorus criterion specified in s. NR 102.06 to determine whether the waterbody is exceeding the criterion. To determine whether additional data are needed to make an attainment decision for section 303 (d) listing purposes, the department shall apply the confidence interval approach described underin s. NR 102.52 (2) (b) to (c). If application of those methods indicates that the waterbody is exceeding the phosphorus criterion, the department shall propose to include the waterbody on the section 303 (d) list as impaired for total phosphorus unless the department determines the waterbody is not exhibiting a biological response to phosphorus as specified in subs. (3) to (6).s. NR 102.60. (3) Combined assessment procedure. (a) This subsection establishes a combined assessment approach for making total phosphorus attainment determinations for surface waters in cases specified in par. (b). This approach is designed to account for variability in how waterbodies respond to phosphorus. The combined approach evaluates a waterbody’s quality by considering its total phosphorus concentration in conjunction with an evaluation of the phosphorus response indicators specified in subs. (4) to (6). The phosphorus response indicators characterize the condition or abundance of aquatic organisms that are responsive to total phosphorus to determine whether aquatic life and recreation uses are being met. Together, the total phosphorus criteria and response indicators may be used to determine whether the phosphorus water quality standards are attained or whether the waterbody should be listed as impaired for total phosphorus on the section 303 (d) list.
(b) 1. If a waterbody exceeds its total phosphorus criterion using the general assessment procedure under sub. (2) and the waterbody’s calculated phosphorus concentration is within the combined assessment range shown in Table C, the department may make the total phosphorus attainment or impairment determination using phosphorus response indicators specified in subs. (4) to (6) if sufficient biological data are available to conduct these assessments. In that case, the following decision protocols apply:
a. A waterbody that attains all of its applicable phosphorus response indicators under subs. (4) to (6) may be excluded from the section 303 (d) listing of waters impaired for phosphorus.
Note: If a waterbody is not considered impaired using the combined approach, it may be a candidate for a less stringent phosphorus site-specific criterion under ch. NR 119. If a waterbody attains its phosphorus criterion but one or more phosphorus response indicators are not attained, it may be a candidate for a more stringent site-specific phosphorus criterion under ch. NR 119. b. If a waterbody does not attain one or more of the applicable phosphorus response indicators in subs. (4) to (6) or if the department does not have sufficient data to evaluate all of the applicable response indicators, then the waterbody shall be considered impaired for total phosphorus and the department shall propose inclusion of the waterbody on the section 303 (d) list as not attaining its phosphorus criterion. As part of the public comment period for the section 303 (d) list, the department shall provide a list of waterbodies needing additional data to determine whether phosphorus response indicators are met. If sufficient phosphorus response indicator data becomes available in the future, the waterbody may be reassessed.
2. If a waterbody exceeds its total phosphorus criterion using the general assessment procedure under sub. (2) and the waterbody’s calculated phosphorus concentration also exceeds the upper limit of the combined assessment range shown in Table C, then the waterbody shall be considered impaired for total phosphorus regardless of attainment of phosphorus response indicators, and the department shall propose to include the waterbody on the section 303 (d) list.
Table C
Range for applying combined assessment for total phosphorus1
Waterbody Type | Total Phosphorus Criterion (ug/L) | Combined Approach Range2 (ug/L total phosphorus) |
Stream or its Impounded Flowing Water | 75 | 75 to <150 |
River or its Impounded Flowing Water | 100 | 100 to <200 |
Unstratified Reservoirs, Unstratified Drainage or Seepage Lakes | 40 | 40 to <60 |
Stratified Reservoirs, Stratified Drainage Lakes | 30 | 30 to <45 |
Stratified Seepage Lakes | 20 | 20 to <30 |
Two-Story Fishery Lakes | 15 | 15 to <22.5 |
1To determine whether a waterbody falls into the combined approach range, compare the lower confidence limit of the waterbody’s two-sided 80% confidence interval around the mean (for lakes/rivers) or median (for rivers/streams) total phosphorus concentration to the ranges in the table.
2For streams and rivers the combined criteria range is between the applicable total phosphorus criterion and two times that criterion. For lakes, the range is between the applicable total phosphorus criterion and 1.5 times that criterion. If a waterbody has an approved site-specific phosphorus criteria, the combined criteria range for that waterbody shall be calculated using these multiplication factors.
(4) Lake and reservoir phosphorus response indicators. A lake or reservoir 5 acres or greater for which the total phosphorus concentration is within the combined approach range specified in Table C shall be listed on the section 303 (d) list as impaired for phosphorus unless it attains all of the following phosphorus response indicators:
(a) Frequency of moderate algae levels. The recreation criteria for frequency of moderate algae levels as specified in s. NR 102.04 (6) (b). (b) Chlorophyll a. The aquatic life criterion for chlorophyll a specified in s. NR 102.04 (4) (f). (c) Aquatic plants. The aquatic plant phosphorus response indicator for aquatic life use that is specified in this paragraph. Aquatic plants, or macrophytes, respond to nutrient enrichment in lakes and reservoirs. Plants are sampled using a grid of sampling points across the lake to determine the proportion of vegetated points that support plant species that are sensitive to or tolerant of high-phosphorus conditions. The resulting percentages are compared to the Macrophyte Assessment of Condition for Phosphorus attainment thresholds shown in Table D. This indicator is attained if the most recent plant survey during the assessment period, or other more representative survey, attains the applicable threshold in Table D.
Table D
Lake aquatic plant community phosphorus response indicator
