Girl Lake
Cass County, Minnesota428 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Girl Lake. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- 2 aquatic invasives
- 81 ft max depth
- Public access
Girl Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 17.6 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 2.7 µg/L. Maximum depth: 81 ft. Surface area: 428.18 acres.
Minnesota DNR's Standard Survey on September 16, 2024 caught 2.00 walleye per gill net at Girl Lake. DNR survey details →
Girl Lake is a 428-acre cold, clear oligotrophic lake in Cass County, Minnesota with a maximum depth of 81 feet. Overall water quality is improving over recent sampling years. The lake supports 18 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 103 other monitored lakes in Cass County, Girl Lake ranks #11 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-29. Methodology: how these readings are compared.
Girl Lake covers about 430 acres in Cass County. It has one public boat landing. If you are planning to stay, you can search lake houses and cabins around Girl Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Girl Lake is good for
From access and monitoring records, not editorial picks.
- Clear water17.6 ft of visibility
- Boat launch1 documented ramp
- Fishing18 species recorded
- Deep water81 ft surveyed max depth
Swimming conditions
Readings onlyLow algae
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. Girl Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Girl 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 Girl Lake
These are the measurements Minnesota PCA publishes for Girl Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 17.6 ft down. Phosphorus 12 µg/L. Chlorophyll-a 2.7 µg/L. TSI 39.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 17.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 12µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.7µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 39 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Girl Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Girl Lake typically sits around 63°F at the surface in September. Summer average is about 68°F. Usually warmest in Jul (about 78°F) and coldest in Aug (about 56°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (56°F) to its warmest (78°F).
Typical surface water temperature by month, from 113 field readings (2011–2024) via the EPA Water Quality Portal. See the full Girl Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Girl Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (108,643 cells/mL) on April 25, 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 September 16, 2024 caught 2.00 walleye per gill net at Girl Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Girl Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
12 surveys on file from MN DNR Fisheries. Most recent: 2024-09-16 (Standard Survey).
12 surveys on file · most recent 2024-09-16 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 15.76 | 3–9 in 2024-09-16 | 0.14 lb |
| Bluntnose Minnow | 12.65 | ||
| Northern Pike | 5.34 | 12–34 in 2024-09-16 | 1.74 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.
Bluegill
Northern Pike
From the 2024-09-16 survey
Girl Lake is a 428-acre lake with 9.4 miles of shoreline and a maximum depth of 81 feet located in Longville, MN. A city owned public access is located on the east shore. The MNDNR has classified Minnesota's lakes into 43 different classes based on physical, chemical, and other characteristics. Moccasin Lake is in…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Girl Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — GirlFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Girl (1581)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — GirlFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — GirlPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
81 ft
Surface area
428 acres
Shoreline
9.4 mi
Littoral zone
64%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Recreation & Access
- Girl 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 Girl Lake
Compare lakeside cabins, hotels, and vacation rentals near Girl Lake in Cass 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.
Top-rated places to stay near Girl Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Girl Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Improving6 years
Phosphorus
Stable-0.23 µg/L/yr6 years
Chlorophyll-a
Improving-0.27 µg/L/yr6 years
EPA Impairment Status
Girl 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.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN11-0174-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Girl Lake under Clean Water Act (NPDES) discharge permits.
- LongvilleLongville · 0.7 mi away · NPDES MN0046655
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.
Nearby Lakes in Cass County
Frequently asked questions about Girl Lake
Where is Girl Lake?
- Girl Lake is a lake in Cass County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Girl Lake?
- Girl Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 17.6 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 2.7 µg/L. Maximum depth: 81 ft. Surface area: 428.18 acres.
Is Girl Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Girl Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Girl Lake?
- Girl Lake typically sits around 63°F at the surface in September, from 113 EPA Water Quality Portal field readings (2011–2024). That is a typical value for the month, not a live reading.
How deep is Girl Lake?
- Girl Lake has a maximum depth of 81 feet. The lake covers 428.18 acres.
What fish are in Girl Lake?
- Fish species found in Girl Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, green sunfish, hybrid sunfish, largemouth bass, muskellunge, northern pike, pumpkinseed, rock bass, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Girl Lake is located in Cass County, Minnesota.
What did the DNR fisheries survey find at Girl Lake?
- Minnesota DNR's Standard Survey on September 16, 2024 caught 2.00 walleye per gill net at Girl Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Girl Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Does Girl Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Girl Lake (clouds, ice, or an off-season gap). The most recent reading was high (108,643 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Girl Lake?
- Girl Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Girl Lake. Public access is listed as yes.
Can I fish at Girl Lake?
- Girl 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 Girl Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Cass County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Brainerd Lakes area
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Mississippi Headwaters, ranked by water quality
Lakes in the Pine River Watersheds (Brainerd Lakes), ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
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Oligotrophic Lakes in Minnesota
Compare Girl Lake With Nearby Lakes
Where this data comes from
109 measurements from 2 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA109 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 (2)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory