Little Rock Lake
Little Rock Lake in Benton County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.8 ft visibility. Phosphorus: 156.5 µg/L. Chlorophyll-a (algae): 115 µg/L. Maximum depth: 17 ft. Surface area: 1310.66 acres.
- Clarity
- 1.8 ft
- Typical in August
- 73°F
- Max depth
- 17 ft
- Area
- 1,311 acres
- Type
- Hypereutrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 10
- Open water
- 229 days
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Little Rock Lake →
Next lake in Benton County
Free interactive depth-contour map of Little Rock Lake, reaching a maximum surveyed depth of 15 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Little Rock Lake is a 1,311-acre highly nutrient-loaded hypereutrophic lake in Benton County, Minnesota with a maximum depth of 17 feet (8-foot average). Water quality is graded F based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 21 documented fish species including bigmouth buffalo, black bullhead, and black crappie. Public access is available with 2 public boat landings.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-17. 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)
Very murky, less than 1.8 ft of visibility. Phosphorus level: 156.5 µg/L. Chlorophyll-a: 115 µg/L. Trophic State Index: 74.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | Not graded |
| Phosphorus | 156.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 115 µg/L | Poor |
| Trophic State Index (TSI) | 74 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Little Rock Lake
Compare lakeside cabins, hotels, and vacation rentals near Little Rock Lake in Benton 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 Little Rock Lake are listed below.
Top-rated places to stay near Little Rock Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Little Rock Lake typically sits around 73°F at the surface in August. Summer average is about 72°F. Usually warmest in Jul (about 74°F) and coldest in Sep (about 58°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 21 field readings (2016–2016) via the EPA Water Quality Portal. See the full Little Rock Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 17 ft |
| Average Depth | 8 ft |
| Surface Area | 1,311 acres |
| Shoreline Length | 10.6 mi |
| Littoral Zone | 95% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Mississippi County ParkPublic
- Benton BeachPublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Little Rock 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.
Source: USGS Nonindigenous Aquatic Species (NAS) Database. Hover a chip to see scientific name, ecological context, status, and first-observed year.
DNR Fisheries Survey Summary
27 surveys on file from MN DNR Fisheries. Most recent: 2025-06-18 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 28.03 | 0.18 lb |
| Walleye | 24.35 | 1.07 lb |
| Black Bullhead | 17.86 | 0.6 lb |
| Black Crappie | 12.57 | 0.28 lb |
| LGP | 12.20 | — |
| Bigmouth Buffalo | 10.83 | 6.59 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.
Yellow Perch
Walleye
Black Bullhead
Black Crappie
From the 2025-06-18 survey
Little Rock Lake (DOW# 05-0013-00; Lake Class 41) is a 1,450-acre reservoir located near Rice, Minnesota. A Minnesota Department of Natural Resources (MNDNR) owned concrete boat ramp is located rear State Highway 10 near the south end of the lake. Little Rock Lake has 10.55 miles of shoreline and a maximum depth of 17…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Little Rock Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Little RockFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Little Rock (1980)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — Little RockPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.017 m/yr | 6 |
| Phosphorus | ↓ Declining | +7.93 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +11.18 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (94 observations).
Estimated open water season: 229 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-09 (2024) | 2018-05-02 (2018) |
| Ice-In | 1991-11-03 (1991) | 2023-12-31 (2023) |
Most recent ice-out: 2025-03-28
EPA Impairment Status
Little Rock 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 MN05-0013-00 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Little Rock Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Rice WwtpRice · 2.9 mi away · NPDES MN0056481Recent violation
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 #1 of 1 lakes in Benton County
Nearby Lakes With Higher Grades
Little Rock Lake holds Grade F. 2 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 Benton County
Frequently asked questions about Little Rock Lake
What is the water quality grade for Little Rock Lake?
- Little Rock Lake in Benton County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.8 ft visibility. Phosphorus: 156.5 µg/L. Chlorophyll-a (algae): 115 µg/L. Maximum depth: 17 ft. Surface area: 1310.66 acres.
Is Little Rock 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. Little Rock Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 115 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Little Rock Lake?
- Little Rock Lake typically sits around 73°F at the surface in August, from 21 EPA Water Quality Portal field readings (2016–2016). That is a typical value for the month, not a live reading.
How deep is Little Rock Lake?
- Little Rock Lake has a maximum depth of 17 feet and an average depth of 8 feet. The lake covers 1310.66 acres.
What fish are in Little Rock Lake?
- Fish species found in Little Rock Lake include bigmouth buffalo, black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, channel catfish, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, shorthead redhorse, silver redhorse, smallmouth bass, walleye, white sucker, yellow bullhead, yellow perch. Little Rock Lake is located in Benton County, Minnesota.
When does Little Rock Lake thaw?
- Little Rock Lake typically has ice-out around Apr 10. Ice typically forms around Nov 25. The open water season is approximately 229 days.
Are there boat ramps on Little Rock Lake?
- Little Rock Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Mississippi County Park, Benton Beach. Public access is listed as yes.
Explore Little Rock 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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Very high nutrients, dense algae, poor clarity
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Where this data comes from
274 measurements from 3 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
MNPCA274 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 (3)
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
Ice data from Minnesota DNR Climate