Malheur Lake
Harney County, OregonView mapDirections
Oregon DEQ publishes the water-quality measurements for Malheur Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Algal growth
- 91 ft max depth
Malheur Lake in Harney County, Oregon has water-quality measurements published by Oregon DEQ, shown here as reported. Phosphorus: 460.5 µg/L. Chlorophyll-a (algae): 45.5 µg/L.
Malheur Lake is a highly nutrient-loaded hypereutrophic lake in Harney County, Oregon with an estimated average depth of about 91 feet. Phosphorus level is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, Oregon DEQ, last sampled 2023-10-19. Methodology: how these readings are compared.
For a place on the water, look through cabin and lake-house rentals near Malheur Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
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. Malheur Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
Whether Malheur Lake is safe to swim in today is a call for the Oregon Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Malheur Lake
These are the measurements Oregon DEQ publishes for Malheur Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 460.5 µg/L. Chlorophyll-a 45.5 µg/L. TSI 80.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 461µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 45.5µg/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. | 80 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Malheur Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~91 ft est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Oregon has not published bathymetry for Malheur Lake.
Lake Size & Watershed
Watershed (drainage) area
4,731 sq mi
HydroLAKES / HydroSHEDS
Surface area
74,201 acres
HydroLAKES / HydroSHEDS
Shoreline
166 mi
HydroLAKES / HydroSHEDS
Elevation
4,091 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 Malheur Lake
Compare lakeside cabins, hotels, and vacation rentals near Malheur Lake in Harney County, Oregon — 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 Malheur Lake are listed below.
Top-rated places to stay near Malheur Lake
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
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Fishing Malheur Lake
Water quality readings over time
2 seasons of samples on record (2021–2023). Calling a direction takes at least 4 years of the same measurement.
Phosphorus
Worsening+196.5 µg/L/yr2 years
Chlorophyll-a
Improving-22.25 µg/L/yr2 years
EPA Impairment Status
Malheur Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Other.
Source: EPA ATTAINS assessment unit OR_LK_1712000107_09_100912 · Official waterbody report
Nearby Lakes in Harney County
Frequently asked questions about Malheur Lake
Where is Malheur Lake?
- Malheur Lake is a lake in Harney County, Oregon. Its water-quality measurements are published by Oregon DEQ and shown on this page as reported.
What is the water quality of Malheur Lake?
- Malheur Lake in Harney County, Oregon has water-quality measurements published by Oregon DEQ, shown here as reported. Phosphorus: 460.5 µg/L. Chlorophyll-a (algae): 45.5 µg/L.
Is Malheur Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Malheur Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
How deep is Malheur Lake?
- No published bathymetric survey covers Malheur Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 91 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Malheur Lake across LakeQuality
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Species activity outlook by water temperature and season
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Where this data comes from
245 measurements from 13 monitoring stations, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Oregon Water Science Center
USGS-OR245 samples · 2020–2023
Analytical methods
- P, wu, WCA, persulfate CF color
- YSI 6025, 470/685 nm, Isochrysis
- Plant pigments, sonication & 445
- YSI Environmental, sensor 6136
Monitoring station identifiers (13)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)