Olathe Lake
Johnson County, Kansas55 acresView mapDirections
KDHE publishes the water-quality measurements for Olathe Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- Limited data
Olathe Lake in Johnson County, Kansas has water-quality measurements published by KDHE, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 50 µg/L. Chlorophyll-a (algae): 14.2 µg/L. Surface area: 55 acres.
Olathe Lake is a 55-acre productive, nutrient-rich eutrophic lake in Johnson County, Kansas. Overall water quality is improving over recent sampling years. Compared to the 12 other monitored lakes in Johnson County, Olathe Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, KDHE, last sampled 2018-09-17. Methodology: how these readings are compared.
Olathe Lake covers about 55 acres in Johnson County. For a place on the water, look through cabin and lake-house rentals near Olathe Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
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. Olathe Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Olathe 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 Olathe Lake
These are the measurements KDHE publishes for Olathe 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 3 ft of visibility. Phosphorus 50 µg/L. Chlorophyll-a 14.2 µg/L. TSI 59.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 50µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 14.2µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 59 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Olathe Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
55 acres
No bathymetric survey has been published for Olathe Lake, so its depth is not documented here.
Stays via Stay22
Stays near Olathe Lake
Compare lakeside cabins, hotels, and vacation rentals near Olathe 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.
Top-rated places to stay near Olathe Lake
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Fishing Olathe Lake
Water Quality Trend: Improving
Based on 5 years of monitoring (2013–2018).
Water clarity
Improving3 years
Phosphorus
Stable-0.22 µg/L/yr5 years
Chlorophyll-a
Stable+0.22 µg/L/yr5 years
Reservoir Info (USACE NID)
Olathe 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
EPA Impairment Status
Olathe Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Drinking water, Aquatic life, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit KS-LM061301 · Official waterbody report
Nearby Lakes in Johnson County
Frequently asked questions about Olathe Lake
Where is Olathe Lake?
- Olathe 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 Olathe Lake?
- Olathe Lake in Johnson County, Kansas has water-quality measurements published by KDHE, shown here as reported. Water clarity: 3 ft visibility. Phosphorus: 50 µg/L. Chlorophyll-a (algae): 14.2 µg/L. Surface area: 55 acres.
Is Olathe Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Olathe Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
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Where this data comes from
60 measurements from 1 monitoring station, 2015–2018. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Kansas Water Science Center
USGS-KS60 samples · 2015–2018
Analytical methods
- Phosphorus, wu, microKJ ASF, H+
- Plant pigments, sonication & 445
- Pigments, algae, EPA445.0 w/ACTN
Monitoring station identifiers (1)
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