Duncan Lake
Stephens County, Oklahoma500 acresView mapDirections
Oklahoma DEQ publishes the water-quality measurements for Duncan Lake. Here is what has been measured.
- Limited data
Duncan Lake in Stephens County, Oklahoma has water-quality measurements published by Oklahoma DEQ, shown here as reported. Water clarity: 4.1 ft visibility. Surface area: 500 acres.
Duncan Lake is a 500-acre lake in Stephens County, Oklahoma.
Source: EPA Water Quality Portal sampling records, ODEQ, last sampled 2019-07-08. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Duncan Lake is safe to swim in today is a call for the Oklahoma Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Duncan Lake
These are the measurements Oklahoma DEQ publishes for Duncan Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 4.1 ft. TSI 57.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 57 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Duncan Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
500 acres
No bathymetric survey has been published for Duncan Lake, so its depth is not documented here.
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Fishing Duncan Lake
Reservoir Info (USACE NID)
Duncan Lake is a man-made reservoir impounded by the Duncan (completed 1937), built primarily for water supply on the Fitzpatrick Creek; earth-type dam, 45 ft tall and 2,650 ft long.
- Surface area
- 500 ac
- Normal storage
- 7,200 ac-ft
- Max storage
- 12,100 ac-ft
- Hazard class
- Significant
- Owner
- CITY OF DUNCAN
Source: USACE National Inventory of Dams, NID ID OK10023 · Operator website
Nearby Lakes in Stephens County
Frequently asked questions about Duncan Lake
Where is Duncan Lake?
- Duncan Lake is a lake in Stephens County, Oklahoma. Its water-quality measurements are published by Oklahoma DEQ and shown on this page as reported.
What is the water quality of Duncan Lake?
- Duncan Lake in Stephens County, Oklahoma has water-quality measurements published by Oklahoma DEQ, shown here as reported. Water clarity: 4.1 ft visibility. Surface area: 500 acres.
Is Duncan Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
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Where this data comes from
12 measurements from 3 monitoring stations, 2018–2019. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- OWRB Lakes Monitoring
OKWRB-LAKES_WQX12 samples · 2018–2019
Analytical methods
- OWRB Lakes Field Data Collection
Monitoring station identifiers (3)
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.