Murphy Lake
Murphy Lake in St. Louis County, Minnesota has a water quality grade of A (Excellent). Water clarity: 6.4 ft visibility. Phosphorus: 18 µg/L. Chlorophyll-a (algae): 6.1 µg/L. Maximum depth: 24 ft. Surface area: 354.16 acres.
- Clarity
- 6.4 ft
- Typical in August
- 71°F
- Max depth
- 24 ft
- Area
- 354 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
Next lake in St. Louis County
Murphy Lake is a 354-acre mesotrophic lake in St. Louis County, Minnesota with a maximum depth of 24 feet (9-foot average). Water quality is graded A based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. The lake supports 10 documented fish species including black crappie, bluegill, and brown bullhead. Public access is available with 2 public boat landings. Compared to the 67 other monitored lakes in St. Louis County, Murphy Lake ranks #21 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-09. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
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)
Murky, only visible to about 6.4 ft. Phosphorus level: 18 µg/L. Chlorophyll-a: 6.1 µg/L. Trophic State Index: 48.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6.4 ft | Not graded |
| Phosphorus | 18 µg/L | Good |
| Chlorophyll-a (Algae) | 6.1 µg/L | Good |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Murphy Lake
Compare lakeside cabins, hotels, and vacation rentals near Murphy Lake in St. Louis 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
Murphy Lake typically sits around 71°F at the surface in August. Summer average is about 68°F. Usually warmest in Aug (about 71°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 67 field readings (2019–2025) via the EPA Water Quality Portal. See the full Murphy Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 24 ft |
| Average Depth | 9 ft |
| Surface Area | 354 acres |
| Shoreline Length | 5.2 mi |
| Littoral Zone | 74% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Murphy LakePublic
- Stone LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Murphy Lake
DNR Fisheries Survey Summary
5 surveys on file from MN DNR Fisheries. Most recent: 2019-07-22 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| GOS | 46.99 | 0.08 lb |
| Largemouth Bass | 22.12 | 1.66 lb |
| Yellow Perch | 15.76 | 0.11 lb |
| Bluegill | 8.40 | 0.14 lb |
| Black Crappie | 5.48 | 0.24 lb |
| Spottail Shiner | 3.75 | — |
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.
GOS
Largemouth Bass
Yellow Perch
Bluegill
From the 2019-07-22 survey
Murphy is a 354 acre lake with 261 (74%) acres of littoral area and maximum depth of 24 feet. Murphy Lake is located just west of Central Lakes, MN off U.S. Highway #53 and has a state-administered, concrete, back-in public access. Murphy was last assessed in 2009. Murphy was surveyed during the summer of 2019 to…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Murphy Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — MurphyFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Murphy (1807)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — MurphyFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — MurphyPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.076 m/yr | 2 |
EPA Impairment Status
Murphy 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 MN69-0646-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Murphy Lake under Clean Water Act (NPDES) discharge permits.
- Great Lakes TransmissionKittson County · 2.2 mi away · NPDES MN0052540
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.
County Ranking
Ranked #21 of 68 lakes in St. Louis County
Nearby Lakes in St. Louis County
Frequently asked questions about Murphy Lake
What is the water quality grade for Murphy Lake?
- Murphy Lake in St. Louis County, Minnesota has a water quality grade of A (Excellent). Water clarity: 6.4 ft visibility. Phosphorus: 18 µg/L. Chlorophyll-a (algae): 6.1 µg/L. Maximum depth: 24 ft. Surface area: 354.16 acres.
Is Murphy Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Murphy Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 6.1 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Murphy Lake?
- Murphy Lake typically sits around 71°F at the surface in August, from 67 EPA Water Quality Portal field readings (2019–2025). That is a typical value for the month, not a live reading.
How deep is Murphy Lake?
- Murphy Lake has a maximum depth of 24 feet and an average depth of 9 feet. The lake covers 354.16 acres.
What fish are in Murphy Lake?
- Fish species found in Murphy Lake include black crappie, bluegill, brown bullhead, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Murphy Lake is located in St. Louis County, Minnesota.
Are there boat ramps on Murphy Lake?
- Murphy Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Murphy Lake, Stone Lake. Public access is listed as yes.
Explore Murphy Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in St. Louis County
Species activity outlook by water temperature and season
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Where to stay at Minnesota's top lakes, each with its grade
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Moderate nutrients, good water quality
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More Minnesota Lake Rankings
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Where this data comes from
51 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
MNPCA51 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 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
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