Riley Lake
Hennepin County, MinnesotaMesotrophic
Riley Lake comes in at a B on the grading rubric — a respectable showing for a Minnesota lake of its size and depth. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.
Mesotrophic conditions dominate at Riley Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. A maximum depth of 49 ft puts Riley Lake in the middle of Minnesota's depth distribution. Riley Lake covers 296 acres alongside 3.3 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Within Hennepin County's 95 graded waters, Riley Lake sits at rank 3, near the top of the local distribution.
Zebra mussels have been documented at Riley Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. The fishery includes walleye among the lake's 11 documented species — a notable draw for Minnesota anglers. A documented public access point at Riley Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-01. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 12.6 ft. Phosphorus level: 20 µg/L. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12.6 ft | B |
| Phosphorus | 20 µg/L | B |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 49 ft |
| Average Depth | 21 ft |
| Surface Area | 296.21 acres |
| Shoreline Length | 3.3 mi |
| Littoral Zone | 37% |
| Public Access | Yes |
Fish Species
Click a species to see all Minnesota and Wisconsin lakes where it is found.
→ Best fishing times for Riley Lake (14-day solunar calendar)
→ Is it safe to eat fish from Riley Lake? (mercury & PFAS guide)
→ Riley Lake fishing regulations (limits, seasons, special rules)
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: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.319 m/yr | 5 |
| Phosphorus | ↓ Declining | +1.14 µg/L/yr | 3 |
Ice Season
Historical ice data from Minnesota DNR (5 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2017-03-23 (2017) | 2006-04-05 (2006) |
| Ice-In | 1993-11-22 (1993) | 1993-11-22 (1993) |
Most recent ice-out: 2017-03-23
Location
County Ranking
Ranked #3 of 95 lakes in Hennepin County
Nearby Lakes in Hennepin County
More Minnesota Lake Rankings
State Parks Near Riley Lake
Other Grade B Lakes in Minnesota
Mesotrophic Lakes in Minnesota
DNR Fisheries Survey Summary
10 surveys on file from MN DNR Fisheries. Most recent: 2021-06-22 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 48.32 | 0.54 lb |
| Bluegill | 34.44 | 0.21 lb |
| Black Crappie | 15.82 | 0.24 lb |
| Yellow Perch | 13.72 | 0.13 lb |
| Brown Bullhead | 7.89 | 0.71 lb |
| Northern Pike | 6.92 | 3.95 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.
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.
- —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
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN10-0002-00 · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate
Most recent sample: 2024-10-01
Monitoring stations: 2