Delavan Lake
Delavan Lake in Walworth County, Wisconsin has a water quality grade of C (Fair). Water clarity: 8.9 ft visibility. Phosphorus: 52.5 µg/L. Chlorophyll-a (algae): 9.1 µg/L. Maximum depth: 52 ft. Surface area: 1906 acres.
Wisconsin DNR rates Panfish as abundant on Delavan Lake. DNR survey details →
- Clarity
- 8.9 ft
- Max depth
- 52 ft
- Area
- 1,906 acres
- Type
- Eutrophic
- Trend
- → Stable
- Public access
- Yes
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Delavan Lake is a 1,906-acre productive, nutrient-rich eutrophic lake in Walworth County, Wisconsin with a maximum depth of 52 feet. Water quality is graded C based on 2 sampling years through 2026. Water clarity is improving over recent sampling years. The lake supports 6 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available. Compared to the 18 other monitored lakes in Walworth County, Delavan Lake ranks #14 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-29. Grade methodology: LakeQuality 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)
Moderate clarity, visible to about 8.9 ft. Phosphorus level: 52.5 µg/L. Chlorophyll-a: 9.1 µg/L. Trophic State Index: 53.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.9 ft | Not graded |
| Phosphorus | 52.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 9.1 µg/L | Good |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Delavan Lake
Compare lakeside cabins, hotels, and vacation rentals near Delavan Lake in Walworth County, Wisconsin — 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 Delavan Lake
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Delavan Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (40,179 cells/mL) on June 27, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Wisconsin DNR rates Panfish as abundant on Delavan Lake.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Delavan Lake C from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1986. 5 stations on file (most recent sample 2026).
Fish Species (DNR-rated)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 52 ft |
| Surface Area | 1,906 acres |
| Public Access | Yes |
Recreation & Access
- Blue Gill RoadPublic
- Delavan Lake Yacht ClubSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Delavan 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: → Stable
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.407 m/yr | 7 |
| Phosphorus | ↓ Declining | +21.38 µg/L/yr | 7 |
| Chlorophyll-a | → Stable | +0.17 µg/L/yr | 4 |
Reservoir Info (USACE NID)
Delavan Lake is a man-made reservoir impounded by the Borg (completed 1935), built primarily for recreation on the TR TURTLE CREEK; gravity-type dam, 12 ft tall and 200 ft long.
- Surface area
- 2,072 ac
- Normal storage
- 12,400 ac-ft
- Max storage
- 21,000 ac-ft
- Drainage area
- 36 sq mi
- Hazard class
- Low
- Owner
- Town Of Delavan
Source: USACE National Inventory of Dams, NID ID WI00702 · Operator website
EPA Impairment Status
Delavan Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit WI10001422 · Official waterbody report
County Ranking
Ranked #14 of 19 lakes in Walworth County
Nearby Lakes With Higher Grades
Delavan Lake holds Grade C. 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 Walworth County
Frequently asked questions about Delavan Lake
Where is Delavan Lake?
- Delavan Lake is a lake in Walworth County, Wisconsin. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Delavan Lake?
- Delavan Lake in Walworth County, Wisconsin has a water quality grade of C (Fair). Water clarity: 8.9 ft visibility. Phosphorus: 52.5 µg/L. Chlorophyll-a (algae): 9.1 µg/L. Maximum depth: 52 ft. Surface area: 1906 acres.
Is Delavan Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Delavan Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 9.1 µg/L. Always check local health department advisories before swimming.
How deep is Delavan Lake?
- Delavan Lake has a maximum depth of 52 feet. The lake covers 1906 acres.
What fish are in Delavan Lake?
- Fish species found in Delavan Lake include Musky, Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Delavan Lake is located in Walworth County, Wisconsin.
What did the DNR fisheries survey find at Delavan Lake?
- Wisconsin DNR rates Panfish as abundant on Delavan Lake. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Delavan Lake C from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
Does Delavan Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Delavan Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (40,179 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
Are there boat ramps on Delavan Lake?
- Delavan Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Blue Gill Road, Delavan Lake Yacht Club. Public access is listed as yes.
Explore Delavan Lake across LakeQuality
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Fish species and best lakes in Walworth County
Species activity outlook by water temperature and season
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High nutrients, frequent algae, reduced clarity
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Where this data comes from
665 measurements from 6 monitoring stations, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX451 samples · 2020–2026 - USGS Wisconsin Water Science Center
USGS-WI214 samples · 2020–2023
Analytical methods
- Phosphorus by Colorimetry
- Turbidity in Water
Monitoring station identifiers (6)
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)
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory