Upper South Long Lake
Upper South Long Lake in Crow Wing County, Minnesota has a water quality grade of C (Fair). Water clarity: 6 ft visibility. Phosphorus: 16 µg/L. Chlorophyll-a (algae): 8.5 µg/L. Maximum depth: 47 ft. Surface area: 804.31 acres.
- Clarity
- 6 ft
- Typical in July
- 65°F
- Max depth
- 47 ft
- Area
- 804 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 15
- Open water
- 232 days
Next lake in Crow Wing County
Free interactive depth-contour map of Upper South Long Lake, reaching a maximum surveyed depth of 45 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Upper South Long Lake is a 804-acre mesotrophic lake in Crow Wing County, Minnesota with a maximum depth of 47 feet. Water quality is graded C based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. The lake supports 16 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 84 other monitored lakes in Crow Wing County, Upper South Long Lake ranks #68 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. 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)
Murky, only visible to about 6 ft. Phosphorus level: 16 µg/L. Chlorophyll-a: 8.5 µg/L. Trophic State Index: 49.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6 ft | Not graded |
| Phosphorus | 16 µg/L | Good |
| Chlorophyll-a (Algae) | 8.5 µg/L | Fair |
| Trophic State Index (TSI) | 49 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Upper South Long Lake
Compare lakeside cabins, hotels, and vacation rentals near Upper South Long Lake in Crow Wing 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
Upper South Long Lake typically sits around 65°F at the surface in July. Summer average is about 65°F. Usually warmest in Jul (about 65°F) and coldest in May (about 51°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 48 field readings (2017–2025) via the EPA Water Quality Portal. See the full Upper South Long Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Upper South Long Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (94,624 cells/mL) on April 21, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 47 ft |
| Surface Area | 804 acres |
| Shoreline Length | 6.3 mi |
| Littoral Zone | 35% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Upper South Long LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Upper South Long 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
11 surveys on file from MN DNR Fisheries. Most recent: 2025-07-21 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Largemouth Bass | 19.39 | 0.92 lb |
| Bluegill | 18.35 | 0.13 lb |
| BKF | 11.34 | — |
| Bluntnose Minnow | 10.90 | — |
| IOD | 7.81 | — |
| Walleye | 6.44 | 1.7 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.
Largemouth Bass
Bluegill
Walleye
From the 2025-07-21 survey
Upper South Long is an 804 acre lake 10 miles southeast of the city of Brainerd in Crow Wing County. Walleye is the primary management species, with the lake being stocked every other year (odd years) with 283 pounds of fingerlings. When surplus Walleye fry are available, up to 300,000 may be stocked; this last…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Upper South Long Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Upper South LongFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Upper South Long (0205)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — Upper South LongFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Upper South LongPublic 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 | +0.357 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.97 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -1.44 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (56 observations).
Estimated open water season: 232 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-13 (2024) | 2013-05-10 (2013) |
| Ice-In | 2010-04-01 (2010) | 1998-12-23 (1998) |
Most recent ice-out: 2025-04-12
EPA Impairment Status
Upper South Long 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 MN18-0096-00 · Official waterbody report
County Ranking
Ranked #68 of 85 lakes in Crow Wing County
Nearby Lakes With Higher Grades
Upper South Long Lake holds Grade C. 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 Crow Wing County
Frequently asked questions about Upper South Long Lake
What is the water quality grade for Upper South Long Lake?
- Upper South Long Lake in Crow Wing County, Minnesota has a water quality grade of C (Fair). Water clarity: 6 ft visibility. Phosphorus: 16 µg/L. Chlorophyll-a (algae): 8.5 µg/L. Maximum depth: 47 ft. Surface area: 804.31 acres.
Is Upper South Long Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Upper South Long Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 8.5 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Upper South Long Lake?
- Upper South Long Lake typically sits around 65°F at the surface in July, from 48 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Upper South Long Lake?
- Upper South Long Lake has a maximum depth of 47 feet. The lake covers 804.31 acres.
What fish are in Upper South Long Lake?
- Fish species found in Upper South Long Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, greater redhorse, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Upper South Long Lake is located in Crow Wing County, Minnesota.
When does Upper South Long Lake thaw?
- Upper South Long Lake typically has ice-out around Apr 15. Ice typically forms around Dec 3. The open water season is approximately 232 days.
Does Upper South Long Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Upper South Long Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (94,624 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Upper South Long Lake?
- Upper South Long Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Upper South Long Lake. Public access is listed as yes.
Explore Upper South Long Lake across LakeGrade
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Where this data comes from
195 measurements from 7 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
MNPCA195 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 (7)
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