Half Moon Lake
Half Moon Lake in Hennepin County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 4.2 ft visibility. Phosphorus: 109.1 µg/L. Chlorophyll-a (algae): 35.6 µg/L. Maximum depth: 25 ft. Surface area: 33.03 acres.
- Clarity
- 4.2 ft
- Typical in August
- 60°F
- Max depth
- 25 ft
- Area
- 33 acres
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- No
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Half Moon Lake →
Next lake in Hennepin County
Half Moon Lake is a 33-acre productive, nutrient-rich eutrophic lake in Hennepin County, Minnesota with a maximum depth of 25 feet. Water quality is graded F based on 3 sampling years through 2024. Overall water quality is improving over recent sampling years. The lake supports 12 documented fish species including black bullhead, black crappie, and bluegill. No public access — the lake is private or restricted. Compared to the 80 other monitored lakes in Hennepin County, Half Moon Lake ranks #72 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-07. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyAlgae risk
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.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Murky, only visible to about 4.2 ft. Phosphorus level: 109.1 µg/L. Chlorophyll-a: 35.6 µg/L. Trophic State Index: 65.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.2 ft | Not graded |
| Phosphorus | 109.1 µg/L | Poor |
| Chlorophyll-a (Algae) | 35.6 µg/L | Poor |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Half Moon Lake
Compare lakeside cabins, hotels, and vacation rentals near Half Moon Lake in Hennepin 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Half Moon Lake are listed below.
Top-rated places to stay near Half Moon Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Half Moon Lake typically sits around 60°F at the surface in August. Summer average is about 59°F. Usually warmest in Jul (about 60°F) and coldest in Jan (about 36°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 973 field readings (2010–2024) via the EPA Water Quality Portal. See the full Half Moon Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 25 ft |
| Surface Area | 33 acres |
| Shoreline Length | 1.2 mi |
| Littoral Zone | 54% |
| Public Access | No |
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Half Moon Lake
DNR Fisheries Survey Summary
5 surveys on file from MN DNR Fisheries. Most recent: 2009-07-06 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 24.04 | 0.48 lb |
| Black Crappie | 20.36 | 0.19 lb |
| Bluegill | 12.80 | 0.16 lb |
| Northern Pike | 6.61 | 2.35 lb |
| Yellow Bass | 3.85 | 0.48 lb |
| Brown Bullhead | 3.48 | 0.68 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.
Black Bullhead
Black Crappie
Bluegill
Northern Pike
From the 2009-07-06 survey
Half Moon is a 30-acre lake located in the Baker Park Reserve operated by the Three Rivers Park District. There is a parking lot, carry-in canoe access, and fishing pier on the west side of the lake. No gas boat motors are permitted. The fishery includes bluegill, black crappie, yellow perch, largemouth bass, and…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Half Moon Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Half MoonFisheries Lake Survey · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.014 m/yr | 6 |
| Phosphorus | ↑ Improving | -12.22 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -5.03 µg/L/yr | 4 |
EPA Impairment Status
Half Moon 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 MN27-0152-00 · Official waterbody report
County Ranking
Ranked #72 of 81 lakes in Hennepin County
Nearby Lakes With Higher Grades
Half Moon Lake holds Grade F. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Hennepin County
Frequently asked questions about Half Moon Lake
What is the water quality grade for Half Moon Lake?
- Half Moon Lake in Hennepin County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 4.2 ft visibility. Phosphorus: 109.1 µg/L. Chlorophyll-a (algae): 35.6 µg/L. Maximum depth: 25 ft. Surface area: 33.03 acres.
Is Half Moon Lake safe to swim in?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Half Moon Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 35.6 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Half Moon Lake?
- Half Moon Lake typically sits around 60°F at the surface in August, from 973 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
How deep is Half Moon Lake?
- Half Moon Lake has a maximum depth of 25 feet. The lake covers 33.03 acres.
What fish are in Half Moon Lake?
- Fish species found in Half Moon Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, hybrid sunfish, largemouth bass, northern pike, walleye, white sucker, yellow bullhead, yellow perch. Half Moon Lake is located in Hennepin County, Minnesota.
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Where this data comes from
287 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA287 samples · 2020–2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 4500 N C ~ Persufate Method for Total Nitrogen
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
Lake details from Minnesota DNR LakeFinder