Agency Bay Lake
Agency Bay Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15.2 ft visibility. Phosphorus: 11 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
- Clarity
- 15.2 ft
- Typical in August
- 61°F
- Type
- Oligotrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 28
- Open water
- 200 days
Next lake in Cass County
Agency Bay Lake is a cold, clear oligotrophic lake in Cass County, Minnesota. Water quality is graded A based on 2 sampling years through 2023. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 103 other monitored lakes in Cass County, Agency Bay Lake ranks #75 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-09-07. 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)
Crystal clear, you can see 15.2 ft down. Phosphorus level: 11 µg/L. Chlorophyll-a: 2.5 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.2 ft | Not graded |
| Phosphorus | 11 µg/L | Good |
| Chlorophyll-a (Algae) | 2.5 µg/L | Good |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Agency Bay Lake
Compare lakeside cabins, hotels, and vacation rentals near Agency Bay 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 Agency Bay Lake
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Water Temperature
Agency Bay Lake typically sits around 61°F at the surface in August. Summer average is about 60°F. Usually warmest in Jul (about 63°F) and coldest in May (about 56°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 316 field readings (2017–2025) via the EPA Water Quality Portal. See the full Agency Bay Lake water temperature breakdown →
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fishing Agency Bay 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.
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Agency Bay Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Public Water Access Sites — Leech (Main Basin)Public 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 | +0.139 m/yr | 6 |
| Phosphorus | → Stable | -0.06 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.2 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (74 observations).
Estimated open water season: 200 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 1945-04-09 (1945) | 1950-05-23 (1950) |
| Ice-In | 2018-11-13 (2018) | 2021-11-25 (2021) |
Most recent ice-out: 2022-05-08
County Ranking
Ranked #75 of 104 lakes in Cass County
Nearby Lakes in Cass County
Frequently asked questions about Agency Bay Lake
What is the water quality grade for Agency Bay Lake?
- Agency Bay Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 15.2 ft visibility. Phosphorus: 11 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
Is Agency Bay Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Agency Bay Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.5 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Agency Bay Lake?
- Agency Bay Lake typically sits around 61°F at the surface in August, from 316 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Agency Bay Lake?
- The available depth estimate for Agency Bay Lake is shallower than its measured water clarity, which cannot be right, so no depth is shown.
When does Agency Bay Lake thaw?
- Agency Bay Lake typically has ice-out around Apr 28. Ice typically forms around Nov 14. The open water season is approximately 200 days.
Explore Agency Bay Lake across LakeGrade
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Where this data comes from
24 measurements from 1 monitoring station, 2022–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Leech Lake Band of Ojibwe
LEECHLAK_WQX24 samples · 2022–2023
Analytical methods
- 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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Ice data from Minnesota DNR Climate