Diamond Lake
Diamond Lake in Kandiyohi County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 5.6 ft visibility. Phosphorus: 65 µg/L. Chlorophyll-a (algae): 17.4 µg/L. Maximum depth: 27 ft. Surface area: 1609.51 acres.
- Clarity
- 5.6 ft
- Typical in August
- 76°F
- Max depth
- 27 ft
- Area
- 1,610 acres
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 15
- Open water
- 237 days
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Diamond Lake →
Next lake in Kandiyohi County
Free interactive depth-contour map of Diamond Lake, reaching a maximum surveyed depth of 25 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Diamond Lake is a 1,610-acre productive, nutrient-rich eutrophic lake in Kandiyohi County, Minnesota with a maximum depth of 27 feet (16-foot average). Water quality is graded D based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. The lake supports 15 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 3 public boat landings. Compared to the 24 other monitored lakes in Kandiyohi County, Diamond Lake ranks #16 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-23. 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.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 5.6 ft. Phosphorus level: 65 µg/L. Chlorophyll-a: 17.4 µg/L. Trophic State Index: 58.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.6 ft | Not graded |
| Phosphorus | 65 µg/L | Poor |
| Chlorophyll-a (Algae) | 17.4 µg/L | Poor |
| Trophic State Index (TSI) | 58 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Diamond Lake
Compare lakeside cabins, hotels, and vacation rentals near Diamond Lake in Kandiyohi 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 Diamond Lake are listed below.
Top-rated places to stay near Diamond Lake
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Planning a trip? Cabins and lodging at Diamond Lake → · more Minnesota lake trips
Water Temperature
Diamond Lake typically sits around 76°F at the surface in August. Summer average is about 75°F. Usually warmest in Jul (about 78°F) and coldest in May (about 62°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 59 field readings (2016–2025) via the EPA Water Quality Portal. See the full Diamond Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 27 ft |
| Average Depth | 16 ft |
| Surface Area | 1,610 acres |
| Shoreline Length | 9.5 mi |
| Littoral Zone | 39% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Kandiyohi County Park No. 3 (West)Public
- Bass LakePublic
- Diamond Lake (East)Public
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Diamond 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 Fisheries Survey Summary
22 surveys on file from MN DNR Fisheries. Most recent: 2025-10-15 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 43.70 | 0.1 lb |
| Bluegill | 24.79 | 0.29 lb |
| Walleye | 24.44 | 1.39 lb |
| Black Bullhead | 22.84 | 0.93 lb |
| Largemouth Bass | 14.92 | 1.12 lb |
| BKF | 11.11 | — |
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 Perch
Bluegill
Walleye
Black Bullhead
From the 2025-10-15 survey
A targeted fall night electrofishing survey was conducted for young of year "YOY" (fingerling sized) Walleye on Diamond Lake during October 15, 2025. A targeted survey is generally used for sampling a specific kind of fish or time of year (i.e., spawning season, fall season, etc.) unlike a standard survey which…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Diamond Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — DiamondFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — DiamondFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — DiamondPublic 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 | +0.185 m/yr | 6 |
| Phosphorus | ↑ Improving | -6.76 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -2.85 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (85 observations).
Estimated open water season: 237 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2017-03-08 (2017) | 2013-05-09 (2013) |
| Ice-In | 2002-11-24 (2002) | 2001-12-20 (2001) |
Most recent ice-out: 2017-03-08
Reservoir Info (USACE NID)
Diamond Lake is a man-made reservoir impounded by the Diamond Lake (completed 1932), built primarily for recreation on the County Ditch 28; gravity-type dam, 7 ft tall and 41 ft long.
- Surface area
- 1,660 ac
- Normal storage
- 38,320 ac-ft
- Max storage
- 44,908 ac-ft
- Drainage area
- 28.1 sq mi
- Hazard class
- Low
- Owner
- County of Kandiyohi
Source: USACE National Inventory of Dams, NID ID MN00069 · Operator website
EPA Impairment Status
Diamond Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN34-0044-00 · Official waterbody report
County Ranking
Ranked #16 of 25 lakes in Kandiyohi County
Nearby Lakes With Higher Grades
Diamond Lake holds Grade D. 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 Kandiyohi County
Frequently asked questions about Diamond Lake
What is the water quality grade for Diamond Lake?
- Diamond Lake in Kandiyohi County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 5.6 ft visibility. Phosphorus: 65 µg/L. Chlorophyll-a (algae): 17.4 µg/L. Maximum depth: 27 ft. Surface area: 1609.51 acres.
Is Diamond Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Diamond Lake has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 17.4 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Diamond Lake?
- Diamond Lake typically sits around 76°F at the surface in August, from 59 EPA Water Quality Portal field readings (2016–2025). That is a typical value for the month, not a live reading.
How deep is Diamond Lake?
- Diamond Lake has a maximum depth of 27 feet and an average depth of 16 feet. The lake covers 1609.51 acres.
What fish are in Diamond Lake?
- Fish species found in Diamond Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Diamond Lake is located in Kandiyohi County, Minnesota.
When does Diamond Lake thaw?
- Diamond Lake typically has ice-out around Apr 15. Ice typically forms around Dec 8. The open water season is approximately 237 days.
Are there boat ramps on Diamond Lake?
- Diamond Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Kandiyohi County Park No. 3 (West), Bass Lake, Diamond Lake (East). Public access is listed as yes.
Explore Diamond Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
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Fish species and best lakes in Kandiyohi County
Species activity outlook by water temperature and season
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Where this data comes from
191 measurements from 4 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
MNPCA191 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (4)
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