Ada Lake
Cass County, Minnesota963 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Ada Lake. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- 60 ft max depth
- Public access
Ada Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 14 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 2.7 µg/L. Maximum depth: 60 ft. Surface area: 963.31 acres.
Minnesota DNR's Standard Survey on July 11, 2022 caught 3.17 walleye per gill net at Ada Lake. DNR survey details →
Free interactive depth-contour map of Ada Lake, reaching a maximum surveyed depth of 60 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Ada Lake is a 963-acre cold, clear oligotrophic lake in Cass County, Minnesota with a maximum depth of 60 feet. Overall water quality is improving over recent sampling years. The lake supports 16 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, Ada Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-25. Methodology: how these readings are compared.
What Ada Lake is good for
From access and monitoring records, not editorial picks.
- Clear water14 ft of visibility
- Boat launch1 documented ramp
- Fishing16 species recorded
- Ice seasonIce-out around Apr 21
- Deep water60 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. Ada Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Ada 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 Ada Lake
These are the measurements Minnesota PCA publishes for Ada Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 14 ft. Phosphorus 10 µg/L. Chlorophyll-a 2.7 µg/L. TSI 39.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 14ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 10µg/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 Ada Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Ada Lake typically sits around 65°F at the surface in September. Summer average is about 67°F. Usually warmest in Jul (about 68°F) and coldest in May (about 55°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (55°F) to its warmest (68°F).
Typical surface water temperature by month, from 247 field readings (2017–2025) via the EPA Water Quality Portal. See the full Ada Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Ada Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (205,116 cells/mL) on May 9, 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 July 11, 2022 caught 3.17 walleye per gill net at Ada Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Ada 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
10 surveys on file from MN DNR Fisheries. Most recent: 2022-07-11 (Standard Survey).
10 surveys on file · most recent 2022-07-11 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluntnose Minnow | 32.08 | ||
| Bluegill | 21.21 | 3–8 in 2022-07-11 | 0.14 lb |
| Yellow Bullhead | 7.06 | 5–12 in 2022-07-11 | 0.54 lb |
| Northern Pike | 5.66 | 13–38 in 2022-07-11 | 1.94 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
Yellow Bullhead
Northern Pike
From the 2022-07-11 survey
Ada Lake is a 963-acre lake with 7.21 miles of shoreline and a maximum depth of 60 feet located east of Backus, MN. A DNR owned public access is located on the northeast shore. The DNR has classified Minnesota's lakes into 43 different classes based on physical, chemical and other characteristics. Ada Lake is in Lake…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Ada Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — AdaFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Ada (1509)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — AdaFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — AdaPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
60 ft
Surface area
963 acres
Shoreline
7.2 mi
Littoral zone
44%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
45 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,319 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Ada 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 Ada Lake
Compare lakeside cabins, hotels, and vacation rentals near Ada 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 Ada Lake
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Fish Species
Click a species to see every lake where it is documented.
Fishing Ada Lake
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Improving6 years
Phosphorus
Worsening+1.25 µg/L/yr2 years
Chlorophyll-a
Improving-0.25 µg/L/yr2 years
Ice season
Typical ice-out
Apr 21
Earliest Mar 24, 2012 · Latest May 14, 2013
Typical ice-in
Nov 25
Earliest Nov 13, 1995 · Latest Dec 21, 2001
Most recent ice-out
May 1
2023
57 observations · Minnesota PCA ice records
EPA Impairment Status
Ada 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 MN11-0250-00 · Official waterbody report
Nearby Lakes in Cass County
Frequently asked questions about Ada Lake
Where is Ada Lake?
- Ada 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 Ada Lake?
- Ada Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 14 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 2.7 µg/L. Maximum depth: 60 ft. Surface area: 963.31 acres.
Is Ada Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Ada 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 Ada Lake?
- Ada Lake typically sits around 65°F at the surface in September, from 247 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Ada Lake?
- Ada Lake has a maximum depth of 60 feet. The lake covers 963.31 acres.
What fish are in Ada Lake?
- Fish species found in Ada Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Ada Lake is located in Cass County, Minnesota.
What did the DNR fisheries survey find at Ada Lake?
- Minnesota DNR's Standard Survey on July 11, 2022 caught 3.17 walleye per gill net at Ada Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Ada 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.
When does Ada Lake thaw?
- Ada Lake typically has ice-out around Apr 21. Ice typically forms around Nov 25. The open water season is approximately 218 days.
Does Ada Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Ada Lake (clouds, ice, or an off-season gap). The most recent reading was high (205,116 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Ada Lake?
- Ada Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Ada Lake. Public access is listed as yes.
Can I fish at Ada Lake?
- Ada 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 Ada Lake across LakeQuality
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Fish species and best lakes in Cass County
Species activity outlook by water temperature and season
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Where to stay at Minnesota's top lakes, each with its readings
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Minnesota's cleanest lakes, ranked on agency measurements
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Where this data comes from
316 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
MNPCA316 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Phosphorus by Colorimetry
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate