Johanna Lake
Johanna Lake in Pope County, Minnesota has a water quality grade of C (Fair). Water clarity: 5.1 ft visibility. Phosphorus: 34.5 µg/L. Chlorophyll-a (algae): 13.4 µg/L. Maximum depth: 10 ft. Surface area: 1399.25 acres.
- Clarity
- 5.1 ft
- Typical in August
- 72°F
- Max depth
- 10 ft
- Area
- 1,399 acres
- Type
- Eutrophic
- Trend
- → Stable
- Public access
- Yes
Next lake in Pope County
Johanna Lake is a 1,399-acre productive, nutrient-rich eutrophic lake in Pope County, Minnesota with a maximum depth of 10 feet (7-foot average). Water quality is graded C based on 2 sampling years through 2025. Water clarity is improving over recent sampling years. The lake supports 11 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 19 other monitored lakes in Pope County, Johanna Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. 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)
Murky, only visible to about 5.1 ft. Phosphorus level: 34.5 µg/L. Chlorophyll-a: 13.4 µg/L. Trophic State Index: 55.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.1 ft | Not graded |
| Phosphorus | 34.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 13.4 µg/L | Fair |
| Trophic State Index (TSI) | 55 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Johanna Lake
Compare lakeside cabins, hotels, and vacation rentals near Johanna Lake in Pope 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
Johanna Lake typically sits around 72°F at the surface in August. Summer average is about 71°F. Usually warmest in Aug (about 72°F) and coldest in Sep (about 67°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 14 field readings (2010–2017) via the EPA Water Quality Portal. See the full Johanna Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Johanna Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (147,231 cells/mL) on July 18, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 10 ft |
| Average Depth | 7 ft |
| Surface Area | 1,399 acres |
| Shoreline Length | 14.6 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Johanna LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Johanna Lake
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2022-06-27 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 31.81 | 0.67 lb |
| Largemouth Bass | 16.29 | 1.14 lb |
| Bluegill | 12.19 | 0.19 lb |
| Brown Bullhead | 7.53 | 0.83 lb |
| Pumpkinseed | 5.85 | 0.07 lb |
| Northern Pike | 4.96 | 2.71 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Black Bullhead
Largemouth Bass
Bluegill
Brown Bullhead
From the 2022-06-27 survey
Lake Johanna is a shallow prairie lake located in southeastern Pope County. The lake is comprised of a large southern basin with a maximum depth of 10 feet, and a northern basin and many smaller bays that are generally less than 6 feet deep. The many shallow bays are often densely vegetated and sustain clearer water.…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Johanna Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — JohannaFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — JohannaFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — JohannaPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.041 m/yr | 6 |
| Phosphorus | → Stable | +0.73 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +1.09 µg/L/yr | 6 |
EPA Impairment Status
Johanna Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN61-0006-00 · Official waterbody report
County Ranking
Ranked #6 of 20 lakes in Pope County
Nearby Lakes With Higher Grades
Johanna Lake holds Grade C. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Pope County
Frequently asked questions about Johanna Lake
What is the water quality grade for Johanna Lake?
- Johanna Lake in Pope County, Minnesota has a water quality grade of C (Fair). Water clarity: 5.1 ft visibility. Phosphorus: 34.5 µg/L. Chlorophyll-a (algae): 13.4 µg/L. Maximum depth: 10 ft. Surface area: 1399.25 acres.
Is Johanna Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Johanna Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 13.4 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Johanna Lake?
- Johanna Lake typically sits around 72°F at the surface in August, from 14 EPA Water Quality Portal field readings (2010–2017). That is a typical value for the month, not a live reading.
How deep is Johanna Lake?
- Johanna Lake has a maximum depth of 10 feet and an average depth of 7 feet. The lake covers 1399.25 acres.
What fish are in Johanna Lake?
- Fish species found in Johanna Lake include black bullhead, black crappie, bluegill, brown bullhead, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead. Johanna Lake is located in Pope County, Minnesota.
Does Johanna Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Johanna Lake (clouds, ice, or an off-season gap). The most recent reading was high (147,231 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Johanna Lake?
- Johanna Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Johanna Lake. Public access is listed as yes.
Explore Johanna Lake across LakeGrade
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Where this data comes from
89 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
MNPCA89 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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory