Pirz Lake
Pirz Lake in Stearns County, Minnesota has a water quality grade of C (Fair). Water clarity: 12 ft visibility. Phosphorus: 26 µg/L. Chlorophyll-a (algae): 6.1 µg/L.
- Clarity
- 12 ft
- Typical in August
- 68°F
- Max depth
- ~38 ft est.
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- No
- Ice-out
- Apr 9
- Open water
- 236 days
Next lake in Stearns County
Pirz Lake is a mesotrophic lake in Stearns County, Minnesota with an estimated average depth of about 38 feet. Water quality is graded C based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 31 other monitored lakes in Stearns County, Pirz Lake ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-15. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyModerate
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Good clarity, visible to about 12 ft. Phosphorus level: 26 µg/L. Chlorophyll-a: 6.1 µg/L. Trophic State Index: 47.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12 ft | Not graded |
| Phosphorus | 26 µg/L | Fair |
| Chlorophyll-a (Algae) | 6.1 µg/L | Good |
| Trophic State Index (TSI) | 47 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Pirz Lake
Compare lakeside cabins, hotels, and vacation rentals near Pirz Lake in Stearns County, Minnesota — 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.
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Water Temperature
Pirz Lake typically sits around 68°F at the surface in August. Summer average is about 66°F. Usually warmest in Aug (about 68°F) and coldest in May (about 53°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 113 field readings (2010–2021) via the EPA Water Quality Portal. See the full Pirz Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~38 ft est. |
| Average Depth | ~11 ft est. |
| Public Access | No |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Pirz Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Pirz Lake
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Pirz Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fish Stocking History — PirzFish Stocking History · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.197 m/yr | 6 |
| Phosphorus | ↓ Declining | +1.63 µg/L/yr | 6 |
| Chlorophyll-a | → Stable | -0.21 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (8 observations).
Estimated open water season: 236 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2016-03-15 (2016) | 2018-04-30 (2018) |
| Ice-In | 2006-11-30 (2006) | 2017-12-09 (2017) |
Most recent ice-out: 2018-04-30
EPA Impairment Status
Pirz Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN73-0196-00 · Official waterbody report · Matched by proximity (2.6 km)
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Pirz Lake under Clean Water Act (NPDES) discharge permits.
- Paul Magedanz Farm 1Richmond · 1.3 mi away · NPDES MN0069841
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 #8 of 32 lakes in Stearns County
Nearby Lakes in Stearns County
Frequently asked questions about Pirz Lake
What is the water quality grade for Pirz Lake?
- Pirz Lake in Stearns County, Minnesota has a water quality grade of C (Fair). Water clarity: 12 ft visibility. Phosphorus: 26 µg/L. Chlorophyll-a (algae): 6.1 µg/L.
Is Pirz Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Pirz Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 6.1 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Pirz Lake?
- Pirz Lake typically sits around 68°F at the surface in August, from 113 EPA Water Quality Portal field readings (2010–2021). That is a typical value for the month, not a live reading.
How deep is Pirz Lake?
- No published bathymetric survey covers Pirz Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 38 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
When does Pirz Lake thaw?
- Pirz Lake typically has ice-out around Apr 9. Ice typically forms around Dec 1. The open water season is approximately 236 days.
Explore Pirz Lake across LakeGrade
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Where this data comes from
104 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA104 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
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)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate