Cedar Lake
Johnson County, Kansas55 acresView mapDirections
KDHE publishes the water-quality measurements for Cedar Lake. Here is what has been measured.
- Hypereutrophic
- 29 ft max depth
Cedar Lake in Johnson County, Kansas has water-quality measurements published by KDHE, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 113 µg/L. Chlorophyll-a (algae): 39.5 µg/L. Surface area: 55 acres.
Cedar Lake is a 55-acre highly nutrient-loaded hypereutrophic lake in Johnson County, Kansas with an estimated average depth of about 29 feet. Overall water quality is declining over recent sampling years. Compared to the 12 other monitored lakes in Johnson County, Cedar Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, KDHE, last sampled 2021-09-14. Methodology: how these readings are compared.
Swimming conditions
Readings onlyAlgae risk
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. Check local advisories before you swim.
Whether Cedar Lake is safe to swim in today is a call for the Kansas Department of Health and Environment and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Cedar Lake
These are the measurements KDHE publishes for Cedar Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 1.6 ft of visibility. Phosphorus 113 µg/L. Chlorophyll-a 39.5 µg/L. TSI 70.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 113µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 39.5µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 70 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Cedar Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~29 ft est.
Surface area
55 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 Cedar Lake.
Lake Size & Watershed
Watershed (drainage) area
12 sq mi
HydroLAKES / HydroSHEDS
Shoreline
1.8 mi
HydroLAKES / HydroSHEDS
Elevation
1,020 ft
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.
Stays via Stay22
Stays near Cedar Lake
Compare lakeside cabins, hotels, and vacation rentals near Cedar Lake in Johnson 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Cedar Lake are listed below.
Top-rated places to stay near Cedar Lake
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Fishing Cedar Lake
Water Quality Trend: Worsening
Based on 7 years of monitoring (2013–2021).
Water clarity
Worsening2 years
Phosphorus
Worsening+49.52 µg/L/yr7 years
Chlorophyll-a
Worsening+1.58 µg/L/yr7 years
Reservoir Info (USACE NID)
Cedar Lake is a man-made reservoir impounded by the Cedar Lake (Old Olathe Lake) (completed 1931), built primarily for water supply on the Cedar Creek-Tr; earth-type dam, 39 ft tall and 800 ft long.
- Surface area
- 55 ac
- Normal storage
- 705 ac-ft
- Max storage
- 1,004 ac-ft
- Drainage area
- 5.97 sq mi
- Hazard class
- High
- Owner
- OLATHE, CITY OF
Source: USACE National Inventory of Dams, NID ID KS02489 · Operator website · Matched by proximity (0.46 km)
Nearby Lakes in Johnson County
Frequently asked questions about Cedar Lake
Where is Cedar Lake?
- Cedar Lake is a lake in Johnson County, Kansas. Its water-quality measurements are published by KDHE and shown on this page as reported.
What is the water quality of Cedar Lake?
- Cedar Lake in Johnson County, Kansas has water-quality measurements published by KDHE, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 113 µg/L. Chlorophyll-a (algae): 39.5 µg/L. Surface area: 55 acres.
Is Cedar Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Cedar Lake?
- No published bathymetric survey covers Cedar Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 29 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 55 acres.
Explore Cedar Lake across LakeQuality
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Other Lakes in Kansas
Hypereutrophic Lakes in Kansas
Where this data comes from
48 measurements from 2 monitoring stations, 2013–2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- EPA R7
EPA_R7_WQX38 samples · 2013–2021 - Kansas Department Of Health And Environment
21KAN001_WQX10 samples · 2013–2017
Analytical methods
- Depth, Secchi disk depth
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Nutrient Analysis
- Chlorophyll a
- Fluorometric Analysis of Chlorophyll a (originally 2334.22A)
Monitoring station identifiers (2)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)