Riley Lake
Hennepin County, Minnesota296 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Riley Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Impaired biota (cause unknown)
- 2 aquatic invasives
- 49 ft max depth
- Public access
Riley Lake in Hennepin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 11.5 ft visibility. Phosphorus: 24 µg/L. Chlorophyll-a (algae): 6.5 µg/L. Maximum depth: 49 ft. Surface area: 296.21 acres.
Minnesota DNR's Standard Survey on June 22, 2021 caught 1.50 walleye per gill net at Riley Lake. DNR survey details →
Riley Lake is a 296-acre mesotrophic lake in Hennepin County, Minnesota with a maximum depth of 49 feet (21-foot average). Overall water quality is declining over recent sampling years. The lake supports 11 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 80 other monitored lakes in Hennepin County, Riley Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-13. Methodology: how these readings are compared.
Riley Lake covers about 300 acres in Hennepin County. It has one public boat landing. The median ice-out date is April 5, which is when the open-water season begins. If you are planning to stay, you can search lake houses and cabins around Riley Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Riley Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11.5 ft of visibility
- Boat launch1 documented ramp
- Fishing11 species recorded
- Ice seasonIce-out around Apr 5
- Deep water49 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. Riley Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Riley 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 Riley Lake
These are the measurements Minnesota PCA publishes for Riley Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 11.5 ft. Phosphorus 24 µg/L. Chlorophyll-a 6.5 µg/L. TSI 47.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 11.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 24µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 6.5µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 47 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Riley Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Riley Lake typically sits around 55°F at the surface in October. Summer average is about 62°F. Usually warmest in Jul (about 63°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 (63°F).
Typical surface water temperature by month, from 1,474 field readings (2010–2025) via the EPA Water Quality Portal. See the full Riley Lake water temperature breakdown →
Minnesota DNR's Standard Survey on June 22, 2021 caught 1.50 walleye per gill net at Riley Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Riley 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
10 surveys on file from MN DNR Fisheries. Most recent: 2021-06-22 (Standard Survey).
10 surveys on file · most recent 2021-06-22 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Black Bullhead | 48.32 | 9–12 in 2021-06-22 | 0.54 lb |
| Bluegill | 34.44 | 2–7 in 2021-06-22 | 0.21 lb |
| Black Crappie | 15.82 | 5–10 in 2021-06-22 | 0.24 lb |
| Yellow Perch | 13.72 | 5–8 in 2021-06-22 | 0.13 lb |
| Brown Bullhead | 7.89 | 6–14 in 2021-06-22 | 0.71 lb |
| Northern Pike | 6.92 | 14–38 in 2021-06-22 | 3.95 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.
Black Bullhead
Bluegill
Black Crappie
Yellow Perch
From the 2021-06-22 survey
Lake Riley is a 296-acre lake with a maximum depth of 49 feet. The lake is located west of Eden Prairie, and Walleye are stocked each year by the lake association. During the summer of 2021, water clarity was neither extremely high nor extremely low, and the lake held good levels of dissolved oxygen to a depth of 32…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Riley Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — RileyFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — RileyFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — RileyPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
49 ft
Average depth
21 ft
Surface area
296 acres
Shoreline
3.3 mi
Littoral zone
37%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
6 sq mi
HydroLAKES / HydroSHEDS
Elevation
856 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Riley LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Riley Lake
Compare lakeside cabins, hotels, and vacation rentals near Riley Lake in Hennepin 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 Riley 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 →
Follow Riley Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Riley 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.
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+3.89 µg/L/yr5 years
Chlorophyll-a
Worsening+3.54 µg/L/yr5 years
Ice season
Typical ice-out
Apr 5
Earliest Mar 23, 2017 · Latest Apr 5, 2006
Most recent ice-out
Mar 23
2017
5 observations · Minnesota PCA ice records
Reservoir Info (USACE NID)
Riley Lake is a man-made reservoir impounded by the Lake Riley (completed 1958), built primarily for recreation on the Riley Creek; gravity-type dam, 9 ft tall and 20 ft long.
- Surface area
- 296 ac
- Normal storage
- 3,000 ac-ft
- Max storage
- 3,900 ac-ft
- Drainage area
- 8.3 sq mi
- Hazard class
- Undetermined
- Owner
- MNDNR
Source: USACE National Inventory of Dams, NID ID MN00411 · Operator website
EPA Impairment Status
Riley Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN10-0002-00 · Official waterbody report
Nearby Lakes in Hennepin County
Frequently asked questions about Riley Lake
Where is Riley Lake?
- Riley Lake is a lake in Hennepin County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Riley Lake?
- Riley Lake in Hennepin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 11.5 ft visibility. Phosphorus: 24 µg/L. Chlorophyll-a (algae): 6.5 µg/L. Maximum depth: 49 ft. Surface area: 296.21 acres.
Is Riley Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Riley Lake is listed impaired under Clean Water Act §303(d) (IR 5) for impaired biota (cause unknown), mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Riley Lake?
- Riley Lake typically sits around 55°F at the surface in October, from 1,474 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Riley Lake?
- Riley Lake has a maximum depth of 49 feet and an average depth of 21 feet. The lake covers 296.21 acres.
What fish are in Riley Lake?
- Fish species found in Riley Lake include black bullhead, black crappie, bluegill, brown bullhead, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, yellow bullhead, yellow perch. Riley Lake is located in Hennepin County, Minnesota.
What did the DNR fisheries survey find at Riley Lake?
- Minnesota DNR's Standard Survey on June 22, 2021 caught 1.50 walleye per gill net at Riley Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Riley 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 Riley Lake thaw?
- Riley Lake typically has ice-out around Apr 5.
Are there boat ramps on Riley Lake?
- Riley Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Riley Lake. Public access is listed as yes.
Can I fish at Riley Lake?
- Riley 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 Riley 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 Hennepin County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Crow River Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Riley Lake
Other Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Where this data comes from
321 measurements from 2 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
MNPCA321 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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 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