Upper Prior Lake
Scott County, Minnesota386 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Upper Prior Lake. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- 2 aquatic invasives
- 50 ft max depth
- Public access
Upper Prior Lake in Scott County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 5 ft visibility. Phosphorus: 38.7 µg/L. Chlorophyll-a (algae): 8.8 µg/L. Maximum depth: 50 ft. Surface area: 386.26 acres.
Minnesota DNR's Targeted Survey on June 23, 2025 caught 1.11 walleye per trap net at Upper Prior Lake. DNR survey details →
Upper Prior Lake is a 386-acre productive, nutrient-rich eutrophic lake in Scott County, Minnesota with a maximum depth of 50 feet. Overall water quality is declining 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 20 other monitored lakes in Scott County, Upper Prior Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-26. Methodology: how these readings are compared.
Upper Prior Lake covers about 390 acres in Scott County. It has one public boat landing. The median ice-out date is April 5, which is when the open-water season begins. Vrbo is where to look for cabins and lake homes around Upper Prior Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Upper Prior Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing16 species recorded
- Ice seasonIce-out around Apr 5
- Deep water50 ft surveyed max depth
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Upper Prior Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Upper Prior Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Upper Prior Lake
These are the measurements Minnesota PCA publishes for Upper Prior Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 5 ft. Phosphorus 38.7 µg/L. Chlorophyll-a 8.8 µg/L. TSI 54.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 38.7µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 8.8µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 54 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Upper Prior Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Upper Prior Lake typically sits around 58°F at the surface in October. Summer average is about 64°F. Usually warmest in Aug (about 66°F) and coldest in Jan (about 37°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (37°F) to its warmest (66°F).
Typical surface water temperature by month, from 1,662 field readings (2010–2025) via the EPA Water Quality Portal. See the full Upper Prior Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on June 23, 2025 caught 1.11 walleye per trap net at Upper Prior Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Upper Prior Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
17 surveys on file from MN DNR Fisheries. Most recent: 2025-06-23 (Targeted Survey).
17 surveys on file · most recent 2025-06-23 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluntnose Minnow | 57.25 | 2 in 2002-07-15 | |
| Bluegill | 47.04 | 3–8 in 2025-06-23 | 0.2 lb |
| Black Crappie | 14.31 | 4–10 in 2025-06-23 | 0.23 lb |
| Yellow Perch | 6.96 | 5 in 2025-06-23 | 0.19 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
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.
Bluntnose Minnow
Bluegill
Black Crappie
Yellow Perch
From the 2025-06-23 survey
A targeted survey of nearshore fish species in Upper Prior Lake was conducted beginning on June 23, 2025, by Lake Biological Monitoring and Assessment (LBMA) Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine,…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Upper Prior Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Upper PriorFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — Upper PriorFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Upper PriorPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
50 ft
Surface area
386 acres
Shoreline
6.2 mi
Littoral zone
85%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Recreation & Access
- DewittPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Upper Prior Lake
Compare lakeside cabins, hotels, and vacation rentals near Upper Prior Lake in Scott 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.
Top-rated places to stay near Upper Prior Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Upper Prior Lake
- → Upper Prior Lake fishing: DNR survey catch rates, species & stocking
- → Upper Prior Lake fishing forecast & best times (species outlook + 14-day solunar calendar)
- → Upper Prior Lake fishing regulations (limits, seasons, special rules)
- → Is it safe to eat fish from Upper Prior Lake? (mercury & PFAS guide)
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+1.73 µg/L/yr6 years
Chlorophyll-a
Stable+0.19 µg/L/yr6 years
Ice season
Typical ice-out
Apr 5
Earliest Mar 3, 2024 · Latest Apr 29, 2013
Typical ice-in
Dec 1
Earliest Nov 6, 1991 · Latest Dec 24, 2001
Most recent ice-out
Mar 24
2025
195 observations · Minnesota PCA ice records
EPA Impairment Status
Upper Prior Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN70-0072-00 · Official waterbody report
Nearby Lakes in Scott County
Frequently asked questions about Upper Prior Lake
Where is Upper Prior Lake?
- Upper Prior Lake is a lake in Scott County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Upper Prior Lake?
- Upper Prior Lake in Scott County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 5 ft visibility. Phosphorus: 38.7 µg/L. Chlorophyll-a (algae): 8.8 µg/L. Maximum depth: 50 ft. Surface area: 386.26 acres.
Is Upper Prior Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Upper Prior Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Upper Prior Lake?
- Upper Prior Lake typically sits around 58°F at the surface in October, from 1,662 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Upper Prior Lake?
- Upper Prior Lake has a maximum depth of 50 feet. The lake covers 386.26 acres.
What fish are in Upper Prior Lake?
- Fish species found in Upper Prior Lake include black bullhead, black crappie, bluegill, brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white bass, white crappie, white sucker, yellow bullhead, yellow perch. Upper Prior Lake is located in Scott County, Minnesota.
What did the DNR fisheries survey find at Upper Prior Lake?
- Minnesota DNR's Targeted Survey on June 23, 2025 caught 1.11 walleye per trap net at Upper Prior Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Upper Prior Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Upper Prior Lake thaw?
- Upper Prior Lake typically has ice-out around Apr 5. Ice typically forms around Dec 1. The open water season is approximately 240 days.
Are there boat ramps on Upper Prior Lake?
- Upper Prior Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Dewitt. Public access is listed as yes.
Can I fish at Upper Prior Lake?
- Upper Prior Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Upper Prior Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Scott County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Minnesota River Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
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State Parks Near Upper Prior Lake
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Compare Upper Prior Lake With Nearby Lakes
Where this data comes from
491 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
MNPCA491 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 4500 N C ~ Persufate Method for Total Nitrogen
- Turbidity, Nephelometric Method
Monitoring station identifiers (3)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate