Delavan Lake
Walworth County, Wisconsin1,906 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Delavan Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 3 aquatic invasives
- 52 ft max depth
- Public access
Delavan Lake in Walworth County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. 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 →
Delavan Lake is a 1,906-acre productive, nutrient-rich eutrophic lake in Walworth County, Wisconsin with a maximum depth of 52 feet. 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 with 2 public boat landings. 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. Methodology: how these readings are compared.
What Delavan Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Fishing6 species recorded
- Deep water52 ft surveyed max depth
- Big water1,906 acres
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. Delavan Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Delavan Lake is safe to swim in today is a call for the Wisconsin Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Delavan Lake
These are the measurements Wisconsin DNR publishes for Delavan Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 8.9 ft. Phosphorus 52.5 µg/L. Chlorophyll-a 9.1 µg/L. TSI 53.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 8.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 52.5µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 9.1µg/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. | 53 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Delavan Lake
Answers come straight from the public measurements and survey records on this page.
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 water quality. LakeQuality shows Delavan Lake’s water-quality measurements separately, 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
Max depth
52 ft
Surface area
1,906 acres
Public access
Yes
Listed by Wisconsin DNR
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
Stays via Stay22
Stays near Delavan Lake
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Fish Species
Click a species to see every 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 (2020–2026).
Water clarity
Improving7 years
Phosphorus
Worsening+21.38 µg/L/yr7 years
Chlorophyll-a
Stable+0.17 µg/L/yr4 years
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
Designated uses not supporting: Recreation.
Source: EPA ATTAINS assessment unit WI10001422 · Official waterbody report
Nearby Lakes in Walworth County
Frequently asked questions about Delavan Lake
Where is Delavan Lake?
- Delavan Lake is a lake in Walworth County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Delavan Lake?
- Delavan Lake in Walworth County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. 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?
- Nutrient and algae readings are not a swimming clearance. Delavan Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
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 water quality. LakeQuality shows Delavan Lake’s water-quality measurements separately, 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.
Can I fish at Delavan Lake?
- Delavan Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Wisconsin's fish and wildlife agency, so check its current regulations before you go.
Explore Delavan Lake across LakeQuality
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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)
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
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory