Ada Lake
Ada Lake in Cass County, Minnesota has a water quality grade of A (Excellent). 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.
- Clarity
- 14 ft
- Typical in August
- 68°F
- Max depth
- 60 ft
- Area
- 963 acres
- Type
- Oligotrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 21
- Open water
- 218 days
Next lake in Cass County
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. Water quality is graded A based on 2 sampling years through 2025. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Good clarity, visible to about 14 ft. Phosphorus level: 10 µg/L. Chlorophyll-a: 2.7 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 14 ft | Not graded |
| Phosphorus | 10 µg/L | Good |
| Chlorophyll-a (Algae) | 2.7 µg/L | Good |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay 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.
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Water Temperature
Ada Lake typically sits around 68°F at the surface in August. 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.
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 ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 60 ft |
| Surface Area | 963 acres |
| Shoreline Length | 7.2 mi |
| Littoral Zone | 44% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Lizzie LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Ada Lake
DNR Fisheries Survey Summary
10 surveys on file from MN DNR Fisheries. Most recent: 2022-07-11 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| MMS | 262.39 | — |
| SFS | 32.51 | — |
| Bluntnose Minnow | 32.08 | — |
| Bluegill | 21.21 | 0.14 lb |
| Yellow Bass | 7.06 | 0.54 lb |
| Northern Pike | 5.66 | 1.94 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.
Bluegill
Yellow Bass
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
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.135 m/yr | 6 |
| Phosphorus | ↓ Declining | +1.25 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -0.25 µg/L/yr | 2 |
Ice Season
Historical ice data from Minnesota DNR (57 observations).
Estimated open water season: 218 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2012-03-24 (2012) | 2013-05-14 (2013) |
| Ice-In | 1995-11-13 (1995) | 2001-12-21 (2001) |
Most recent ice-out: 2023-05-01
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN11-0250-00 · Official waterbody report
County Ranking
Ranked #4 of 104 lakes in Cass County
Nearby Lakes in Cass County
Frequently asked questions about Ada Lake
What is the water quality grade for Ada Lake?
- Ada Lake in Cass County, Minnesota has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. Ada Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.7 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Ada Lake?
- Ada Lake typically sits around 68°F at the surface in August, 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.
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 Lizzie Lake. Public access is listed as yes.
Explore Ada Lake across LakeGrade
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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)
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
Ice data from Minnesota DNR Climate