Hammal Lake
Hammal Lake in Aitkin County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 12.5 ft visibility. Maximum depth: 44 ft. Surface area: 375.52 acres.
- Clarity
- 12.5 ft
- Typical in August
- 65°F
- Max depth
- 44 ft
- Area
- 376 acres
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 13
- Open water
- 228 days
Next lake in Aitkin County
Why Hammal Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Hammal Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Hammal Lake is a 376-acre lake in Aitkin County, Minnesota with a maximum depth of 44 feet (11-foot average). Overall water quality is declining over recent sampling years. The lake supports 14 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-03. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Hammal Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 12.5 ft. Trophic State Index: 41.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Hammal Lake
Compare lakeside cabins, hotels, and vacation rentals near Hammal Lake in Aitkin 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 Hammal Lake
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Water Temperature
Hammal Lake typically sits around 65°F at the surface in August. Summer average is about 64°F. Usually warmest in Jul (about 66°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 48 field readings (2016–2025) via the EPA Water Quality Portal. See the full Hammal Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 44 ft |
| Average Depth | 10.5 ft |
| Surface Area | 376 acres |
| Shoreline Length | 4.6 mi |
| Littoral Zone | 70% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Hammal LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Hammal Lake
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2022-08-15 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Bass | 21.78 | 0.49 lb |
| Bluegill | 19.86 | 0.17 lb |
| BNS | 13.29 | — |
| GOS | 11.87 | — |
| Largemouth Bass | 11.07 | 1.19 lb |
| Bluntnose Minnow | 10.55 | — |
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.
Yellow Bass
Bluegill
Largemouth Bass
From the 2022-08-15 survey
Hammal Lake is a moderate sized lake located a few miles southwest of the City of Aitkin. The lake has diverse habitat including shallow vegetated bays, submerged points, and deep holes. Residential development ranging from seasonal cabins to year-round homes occurs around much of the shoreline. There is a public…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Hammal Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — HammalFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Hammal (0048)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — HammalPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.128 m/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (24 observations).
Estimated open water season: 228 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2017-03-30 (2017) | 2022-05-04 (2022) |
| Ice-In | 2019-11-08 (2019) | 2004-12-14 (2004) |
Most recent ice-out: 2024-04-02
EPA Impairment Status
Hammal 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 MN01-0161-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Hammal Lake under Clean Water Act (NPDES) discharge permits.
- Aitkin WwtpAitkin · 4.5 mi away · NPDES MN0020095
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.
Graded lakes near Hammal Lake
Hammal Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Aitkin County
Frequently asked questions about Hammal Lake
What is the water quality grade for Hammal Lake?
- Hammal Lake in Aitkin County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 12.5 ft visibility. Maximum depth: 44 ft. Surface area: 375.52 acres.
Is Hammal Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Hammal Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
What is the water temperature of Hammal Lake?
- Hammal Lake typically sits around 65°F at the surface in August, from 48 EPA Water Quality Portal field readings (2016–2025). That is a typical value for the month, not a live reading.
How deep is Hammal Lake?
- Hammal Lake has a maximum depth of 44 feet and an average depth of 10.5 feet. The lake covers 375.52 acres.
What fish are in Hammal Lake?
- Fish species found in Hammal Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, walleye, yellow bullhead, yellow perch. Hammal Lake is located in Aitkin County, Minnesota.
When does Hammal Lake thaw?
- Hammal Lake typically has ice-out around Apr 13. Ice typically forms around Nov 27. The open water season is approximately 228 days.
Are there boat ramps on Hammal Lake?
- Hammal Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Hammal Lake. Public access is listed as yes.
Explore Hammal Lake across LakeGrade
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Where this data comes from
25 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
MNPCA25 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
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