Hill Slough Lake
Hill Slough Lake in Sauk County, Wisconsin has a water quality grade of D (Nutrient-rich). Water clarity: 4.4 ft visibility. Phosphorus: 42.7 µg/L.
- Clarity
- 4.4 ft
- Typical in August
- 57°F
- Type
- Eutrophic
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Hill Slough Lake →
Next lake in Sauk County
Hill Slough Lake is a productive, nutrient-rich eutrophic lake in Sauk County, Wisconsin. Water quality is graded D based on 1 sampling years through 2025. Compared to the 6 other monitored lakes in Sauk County, Hill Slough Lake ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-10-29. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 4.4 ft. Phosphorus level: 42.7 µg/L. Trophic State Index: 57.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.4 ft | Not graded |
| Phosphorus | 42.7 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 57 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Hill Slough Lake
Compare lakeside cabins, hotels, and vacation rentals near Hill Slough Lake in Sauk County, Wisconsin — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Hill Slough Lake are listed below.
Top-rated places to stay near Hill Slough Lake
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Water Temperature
Hill Slough Lake typically sits around 57°F at the surface in August. Summer average is about 67°F. Usually warmest in Jun (about 77°F) and coldest in Oct (about 49°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 19 field readings (2025–2025) via the EPA Water Quality Portal. See the full Hill Slough Lake water temperature breakdown →
Fishing Hill Slough Lake
EPA Impairment Status
Hill Slough Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit WI10028530 · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Hill Slough Lake under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Spring Green Golf Club Sanitary Dist #2 WwtfWyoming · 1.3 mi away · NPDES WI0028363Recent violation
- Spring Green Wastewater Treatment FacilitySpring Green · 1.6 mi away · NPDES WI0060801Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #7 of 7 lakes in Sauk County
Nearby Lakes With Higher Grades
Hill Slough Lake holds Grade D. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Sauk County
Frequently asked questions about Hill Slough Lake
What is the water quality grade for Hill Slough Lake?
- Hill Slough Lake in Sauk County, Wisconsin has a water quality grade of D (Nutrient-rich). Water clarity: 4.4 ft visibility. Phosphorus: 42.7 µg/L.
Is Hill Slough Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Hill Slough Lake has a water quality grade of D (Nutrient-rich). Always check local health department advisories before swimming.
What is the water temperature of Hill Slough Lake?
- Hill Slough Lake typically sits around 57°F at the surface in August, from 19 EPA Water Quality Portal field readings (2025–2025). That is a typical value for the month, not a live reading.
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Where this data comes from
14 measurements from 2 monitoring stations, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX14 samples · 2025
Analytical methods
- Phosphorus by Colorimetry
- Turbidity in Water
Monitoring station identifiers (2)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)