Johanna Lake
Pope County, Minnesota1,399 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Johanna Lake. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- 10 ft max depth
- Public access
Johanna Lake in Pope County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. 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.
Minnesota DNR's Standard Survey on June 27, 2022 caught 1.00 walleye per gill net at Johanna Lake. DNR survey details →
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 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. Methodology: how these readings are compared.
What Johanna Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing11 species recorded
- Big water1,399 acres
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Johanna Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Johanna Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Johanna Lake
These are the measurements Minnesota PCA publishes for Johanna Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 5.1 ft. Phosphorus 34.5 µg/L. Chlorophyll-a 13.4 µg/L. TSI 55.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 34.5µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 13.4µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 55 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Johanna Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Johanna Lake typically sits around 67°F at the surface in September. 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.
Column height runs from this lake’s coldest month (67°F) to its warmest (72°F).
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 ↗
Minnesota DNR's Standard Survey on June 27, 2022 caught 1.00 walleye per gill net at Johanna Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Johanna Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2022-06-27 (Standard Survey).
8 surveys on file · most recent 2022-06-27 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Black Bullhead | 31.81 | 4–11 in 2022-06-27 | 0.67 lb |
| Largemouth Bass | 16.29 | 3–16 in 2022-06-27 | 1.14 lb |
| Bluegill | 12.19 | 2–9 in 2022-06-27 | 0.19 lb |
| Brown Bullhead | 7.53 | 5–16 in 2022-06-27 | 0.83 lb |
| Pumpkinseed | 5.85 | 3–7 in 2022-06-27 | 0.07 lb |
| Northern Pike | 4.96 | 17–31 in 2022-06-27 | 2.71 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
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
Lake Details
Max depth
10 ft
Average depth
7 ft
Surface area
1,399 acres
Shoreline
14.6 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
6 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,296 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Johanna LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Johanna Lake
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Fish Species
Click a species to see every lake where it is documented.
Fishing Johanna Lake
Water Quality Trend: Stable
Based on 6 years of monitoring (2020–2025).
Water clarity
Improving6 years
Phosphorus
Stable+0.73 µg/L/yr6 years
Chlorophyll-a
Worsening+1.09 µg/L/yr6 years
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
Designated uses not supporting: Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN61-0006-00 · Official waterbody report
Nearby Lakes in Pope County
Frequently asked questions about Johanna Lake
Where is Johanna Lake?
- Johanna Lake is a lake in Pope County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Johanna Lake?
- Johanna Lake in Pope County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. 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?
- Nutrient and algae readings are not a swimming clearance. Johanna Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Johanna Lake?
- Johanna Lake typically sits around 67°F at the surface in September, 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.
What did the DNR fisheries survey find at Johanna Lake?
- Minnesota DNR's Standard Survey on June 27, 2022 caught 1.00 walleye per gill net at Johanna Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Johanna Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
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.
Can I fish at Johanna Lake?
- Johanna Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Johanna Lake across LakeQuality
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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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from 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