Third River Flowage Lake
Third River Flowage Lake in Itasca County, Minnesota has a water quality grade of C (Fair). Water clarity: 6.9 ft visibility. Phosphorus: 28.5 µg/L. Chlorophyll-a (algae): 5.5 µg/L. Maximum depth: 69.8 ft. Surface area: 56471.4 acres.
- Clarity
- 6.9 ft
- Typical in August
- 70°F
- Max depth
- 69.8 ft
- Area
- 56,471 acres
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 27
Next lake in Itasca County
Third River Flowage Lake is a 56,471-acre mesotrophic lake in Itasca County, Minnesota with a maximum depth of 70 feet (15-foot average). Water quality is graded C based on 3 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 20 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 71 other monitored lakes in Itasca County, Third River Flowage Lake ranks #61 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-14. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyModerate
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Moderate clarity, visible to about 6.9 ft. Phosphorus level: 28.5 µg/L. Chlorophyll-a: 5.5 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6.9 ft | Not graded |
| Phosphorus | 28.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 5.5 µg/L | Good |
| Trophic State Index (TSI) | 50 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Third River Flowage Lake
Compare lakeside cabins, hotels, and vacation rentals near Third River Flowage Lake in Itasca 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
Third River Flowage Lake typically sits around 70°F at the surface in August. Summer average is about 69°F. Usually warmest in Jul (about 74°F) and coldest in Oct (about 52°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 43 field readings (2024–2025) via the EPA Water Quality Portal. See the full Third River Flowage Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 69.8 ft |
| Average Depth | 15.1 ft |
| Surface Area | 56,471 acres |
| Shoreline Length | 69.8 mi |
| Littoral Zone | 33% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Third River FlowagePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Third River Flowage 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
38 surveys on file from MN DNR Fisheries. Most recent: 2024-05-16 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 227.14 | 0.19 lb |
| Spottail Shiner | 109.89 | — |
| MMS | 75.59 | — |
| Bluntnose Minnow | 22.18 | — |
| Walleye | 20.75 | 1.18 lb |
| SUN | 13.15 | — |
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
Walleye
From the 2024-05-16 survey
Lake Winnibigoshish, otherwise known as Winnie or Big Winnie, is a large reservoir located immediately north of the community of Bena, Minnesota. Winnie was a natural lake that was impounded in the 1880's with a dam controlled by the U.S. Army Corps of Engineers (USACE). Today the USACE maintains water levels within a…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Third River Flowage Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — WinnibigoshishFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Winnibigoshish (0702)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — WinnibigoshishFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — WinnibigoshishPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.17 m/yr | 2 |
| Phosphorus | ↓ Declining | +3.5 µg/L/yr | 2 |
| Chlorophyll-a | ↓ Declining | +0.5 µg/L/yr | 2 |
Ice Season
Historical ice data from Minnesota DNR (32 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2012-03-30 (2012) | 2013-05-17 (2013) |
| Ice-In | 2023-11-29 (2023) | 2019-12-02 (2019) |
Most recent ice-out: 2025-04-29
County Ranking
Ranked #61 of 72 lakes in Itasca County
Nearby Lakes in Itasca County
Frequently asked questions about Third River Flowage Lake
What is the water quality grade for Third River Flowage Lake?
- Third River Flowage Lake in Itasca County, Minnesota has a water quality grade of C (Fair). Water clarity: 6.9 ft visibility. Phosphorus: 28.5 µg/L. Chlorophyll-a (algae): 5.5 µg/L. Maximum depth: 69.8 ft. Surface area: 56471.4 acres.
Is Third River Flowage Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Third River Flowage Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 5.5 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Third River Flowage Lake?
- Third River Flowage Lake typically sits around 70°F at the surface in August, from 43 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Third River Flowage Lake?
- Third River Flowage Lake has a maximum depth of 69.8 feet and an average depth of 15.1 feet. The lake covers 56471.4 acres.
What fish are in Third River Flowage Lake?
- Fish species found in Third River Flowage Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, burbot, hybrid sunfish, largemouth bass, muskellunge, northern pike, pumpkinseed, rock bass, shorthead redhorse, silver redhorse, sunfish, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Third River Flowage Lake is located in Itasca County, Minnesota.
When does Third River Flowage Lake thaw?
- Third River Flowage Lake typically has ice-out around Apr 27.
Are there boat ramps on Third River Flowage Lake?
- Third River Flowage Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Third River Flowage. Public access is listed as yes.
Explore Third River Flowage Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
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Species activity outlook by water temperature and season
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Moderate nutrients, good water quality
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Where this data comes from
42 measurements from 1 monitoring station, 2024–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Leech Lake Band of Ojibwe
LEECHLAK_WQX42 samples · 2024–2025
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Nitrate-Nitrite Nitrogen by Colorimetry
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)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate