New Olathe Lake
Johnson County, Kansas165 acresView mapDirections
KDHE publishes the water-quality measurements for New Olathe Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- Limited data
New Olathe Lake in Johnson County, Kansas has water-quality measurements published by KDHE, shown here as reported. Water clarity: 3.4 ft visibility. Phosphorus: 29 µg/L. Chlorophyll-a (algae): 10 µg/L. Surface area: 165 acres.
New Olathe Lake is a 165-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, New Olathe Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, KDHE, last sampled 2018-08-06. Methodology: how these readings are compared.
New Olathe Lake covers about 170 acres in Johnson County. If you are planning to stay, you can search lake houses and cabins around New Olathe Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
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. New Olathe Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether New 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 New Olathe Lake
These are the measurements KDHE publishes for New Olathe 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 3.4 ft. Phosphorus 29 µg/L. Chlorophyll-a 10 µg/L. TSI 55.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.4ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 29µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 10µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 55 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about New Olathe Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
165 acres
No bathymetric survey has been published for New Olathe Lake, so its depth is not documented here.
Stays via Stay22
Stays near New Olathe Lake
Compare lakeside cabins, hotels, and vacation rentals near New 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.
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Fishing New 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)
New Olathe Lake is a man-made reservoir impounded by the (New) Olathe Lake (completed 1955), built primarily for water supply on the Cedar Creek; earth-type dam, 69 ft tall and 1,350 ft long.
- Surface area
- 165 ac
- Normal storage
- 3,330 ac-ft
- Max storage
- 5,626 ac-ft
- Drainage area
- 16.9 sq mi
- Hazard class
- High
- Owner
- OLATHE, CITY OF
Source: USACE National Inventory of Dams, NID ID KS02490 · Operator website
EPA Impairment Status
New 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 New Olathe Lake
Where is New Olathe Lake?
- New 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 New Olathe Lake?
- New Olathe Lake in Johnson County, Kansas has water-quality measurements published by KDHE, shown here as reported. Water clarity: 3.4 ft visibility. Phosphorus: 29 µg/L. Chlorophyll-a (algae): 10 µg/L. Surface area: 165 acres.
Is New Olathe Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. New 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
7 measurements from 1 monitoring station, 2013–2018. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Kansas Department Of Health And Environment
21KAN001_WQX7 samples · 2013–2018
Analytical methods
- Depth, Secchi disk depth
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
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