Marion Co Lake
Marion County, Kansas150 acresView mapDirections
Nutrients and algae run well above the regional average.
↓ down from D at the last regrade
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- #2 of 2 in the county
- 51 ft max depth
- Limited data
Marion Co Lake in Marion County, Kansas has a water quality grade of F (Algae-prone). Water clarity: 2.9 ft visibility. Phosphorus: 82.5 µg/L. Chlorophyll-a (algae): 41.6 µg/L. Surface area: 150 acres.
- Clarity
- 2.9 ft
- Max depth
- ~51 ft est.
- Area
- 150 acres
- Type
- Hypereutrophic
- Phosphorus
- 82.5 µg/L
- Chlorophyll-a
- 41.6 µg/L
- Trend
- ↓ Declining
Stays via Stay22
Stays near Marion Co Lake
Compare lakeside cabins, hotels, and vacation rentals near Marion Co Lake in Marion County, Kansas — 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 Marion Co Lake are listed below.
Top-rated places to stay near Marion Co Lake
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Watch Marion Co Lake’s letter
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Marion Co Lake is a 150-acre highly nutrient-loaded hypereutrophic lake in Marion County, Kansas with an estimated average depth of about 51 feet. Water quality is graded F based on 1 sampling years through 2018. Overall water quality is declining over recent sampling years. Compared to the 1 other monitored lakes in Marion County, Marion Co Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, KDHE, last sampled 2018-07-31. Grade methodology: LakeQuality methodology.
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 F is nutrients and algae, not a swimming clearance. Marion Co Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen), oxygen depletion (low DO). Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 2.9 ft of visibility. Phosphorus 82.5 µg/L. Chlorophyll-a 41.6 µg/L. TSI 66. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.9 ft | Not graded |
| Phosphorus | 82.5 µg/L | Not graded |
| Chlorophyll-a (Algae) | 41.6 µg/L | Poor |
| Trophic State Index (TSI) | 66 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~51 ft est. |
| Average Depth | ~11 ft est. |
| Surface Area | 150 acres |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Kansas has not published bathymetry for Marion Co 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.
Fishing Marion Co Lake
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.033 m/yr | 2 |
| Phosphorus | ↑ Improving | -2.67 µg/L/yr | 2 |
| Chlorophyll-a | ↓ Declining | +4.02 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Marion Co Lake is a man-made reservoir impounded by the Marion County Lake Dam (completed 1937), built primarily for recreation on the Cottonwood River-Tr, 62 ft tall and 1,290 ft long.
- Surface area
- 150 ac
- Normal storage
- 2,418 ac-ft
- Max storage
- 4,063 ac-ft
- Drainage area
- 7.2 sq mi
- Hazard class
- Significant
- Owner
- MARION COUNTY
Source: USACE National Inventory of Dams, NID ID KS02548 · Operator website · Matched by proximity (0.16 km)
EPA Impairment Status
Marion Co Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit KS-LM012101 · Official waterbody report
County Ranking
Ranked #2 of 2 lakes in Marion County
Nearby Lakes in Marion County
Frequently asked questions about Marion Co Lake
Where is Marion Co Lake?
- Marion Co Lake is a lake in Marion County, Kansas. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Marion Co Lake?
- Marion Co Lake in Marion County, Kansas has a water quality grade of F (Algae-prone). Water clarity: 2.9 ft visibility. Phosphorus: 82.5 µg/L. Chlorophyll-a (algae): 41.6 µg/L. Surface area: 150 acres.
Is Marion Co Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Marion Co Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen), oxygen depletion (low DO). Check local advisories before you swim.
How deep is Marion Co Lake?
- No published bathymetric survey covers Marion Co Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 51 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 150 acres.
Explore Marion Co Lake across LakeQuality
More Kansas Lake Rankings
Other Grade F Lakes in Kansas
Hypereutrophic Lakes in Kansas
Where this data comes from
8 measurements from 1 monitoring station, 2012–2018. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Kansas Department Of Health And Environment
21KAN001_WQX8 samples · 2012–2018
Analytical methods
- Depth, Secchi disk depth
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
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)