Copan Lake
Washington County, Oklahoma4,850 acresView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- Impaired · Algal growth
- #1 of 1 in the county
- 62 ft max depth
- Public access
- Limited data
Copan Lake in Washington County, Oklahoma has a water quality grade of D (Nutrient-rich). Water clarity: 1.6 ft visibility. Phosphorus: 79 µg/L. Surface area: 4850 acres.
- Clarity
- 1.6 ft
- Max depth
- ~62 ft est.
- Area
- 4,850 acres
- Type
- Eutrophic
- Phosphorus
- 79 µg/L
- Public access
- Yes
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Stays near Copan Lake
Compare lakeside cabins, hotels, and vacation rentals near Copan Lake in Washington County, Oklahoma — 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Copan Lake are listed below.
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Copan Lake is a 4,850-acre productive, nutrient-rich eutrophic lake in Washington County, Oklahoma with an estimated average depth of about 62 feet. Water quality is graded D based on 1 sampling years through 2023. Limited fish-species data available. Public access is available with 3 public boat landings.
Source: EPA Water Quality Portal sampling records, ODEQ, last sampled 2023-09-25. Grade methodology: LakeQuality methodology.
What Copan Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch3 documented ramps
- Big water4,850 acres
Swimming Safety
Grade onlyLimited data
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.
The D is nutrients and algae, not a swimming clearance. Copan Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, mercury, turbidity. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 1.6 ft of visibility. Phosphorus 79 µg/L. TSI 69. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 79 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 69 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~62 ft est. |
| Surface Area | 4,850 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Oklahoma has not published bathymetry for Copan Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Copan PointPublic
- Washington Cove ParkPublic
- Osage Plains ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Copan Lake
Reservoir Info (USACE NID)
Copan Lake is a man-made reservoir impounded by the Copan Dam (completed 1983), built primarily for flood risk reduction on the Little Caney; earth-type dam, 73 ft tall and 7,730 ft long.
- Surface area
- 4,850 ac
- Normal storage
- 43,400 ac-ft
- Max storage
- 338,000 ac-ft
- Drainage area
- 505 sq mi
- Hazard class
- High
- Owner
- USACE - Tulsa District
All listed purposes: Flood Risk Reduction;Other;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID OK21489 · Operator website
EPA Impairment Status
Copan Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit OK121400050020_00 · Official waterbody report
County Ranking
Ranked #1 of 1 lakes in Washington County
Nearby Lakes in Washington County
Frequently asked questions about Copan Lake
Where is Copan Lake?
- Copan Lake is a lake in Washington County, Oklahoma. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Copan Lake?
- Copan Lake in Washington County, Oklahoma has a water quality grade of D (Nutrient-rich). Water clarity: 1.6 ft visibility. Phosphorus: 79 µg/L. Surface area: 4850 acres.
Is Copan Lake safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Copan Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, mercury, turbidity. Check local advisories before you swim.
How deep is Copan Lake?
- No published bathymetric survey covers Copan Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 62 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 4850 acres.
Are there boat ramps on Copan Lake?
- Copan Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Copan Point, Washington Cove Park, Osage Plains Park. Public access is listed as yes.
Explore Copan Lake across LakeQuality
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Other Grade D Lakes in Oklahoma
Eutrophic Lakes in Oklahoma
Where this data comes from
53 measurements from 7 monitoring stations, 2017–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- OWRB Lakes Monitoring
OKWRB-LAKES_WQX35 samples · 2017–2023 - Cherokee Nation (Tribal)
CHEROKEE_WQX18 samples · 2018
Analytical methods
- OWRB Lakes Field Data Collection
- Determination of Turbidity
- CN_QAPP
Monitoring station identifiers (7)
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)
Named boat-access points from the USGS National Boat Ramps inventory