Fourmile Lake
Klamath County, Oregon962 acresView mapDirections
Oregon DEQ publishes the water-quality measurements for Fourmile Lake. Here is what has been measured.
- Oligotrophic
- 47 ft max depth
- Public access
- Limited data
Fourmile Lake in Klamath County, Oregon has water-quality measurements published by Oregon DEQ, shown here as reported. Chlorophyll-a (algae): 0.5 µg/L. Surface area: 962 acres.
Fourmile Lake is a 962-acre cold, clear oligotrophic lake in Klamath County, Oregon with an estimated average depth of about 47 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 16 other monitored lakes in Klamath County, Fourmile Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Oregon DEQ, last sampled 2025-10-01. Methodology: how these readings are compared.
What Fourmile Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Camping1 public campground nearby
Swimming conditions
Readings onlyLimited data
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 Fourmile 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 Fourmile Lake
These are the measurements Oregon DEQ publishes for Fourmile 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. Chlorophyll-a 0.5 µg/L. TSI 23.
| 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 | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | 0.5µg/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. | 23 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Fourmile Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~47 ft est.
Surface area
962 acres
Public access
Yes
Listed by Oregon DEQ
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Oregon has not published bathymetry for Fourmile Lake.
Lake Size & Watershed
Watershed (drainage) area
10 sq mi
HydroLAKES / HydroSHEDS
Shoreline
5.8 mi
HydroLAKES / HydroSHEDS
Elevation
5,761 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.
Recreation & Access
- Fourmile Lake CampgroundPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Public campgrounds near Fourmile Lake
- Fourmile Lake Campground0.3 km
Nearest public campgrounds in the USGS National Map inventory, within about 3 miles. An empty list means USGS records no campground that close, which is not the same as camping being unavailable. Where the source gives an official reservation link, it is used; the cabin and hotel search does not cover campsites. More camping lakes
Stays via Stay22
Stays near Fourmile Lake
Compare lakeside cabins, hotels, and vacation rentals near Fourmile Lake in Klamath 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.
Top-rated places to stay near Fourmile Lake
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Planning a trip? Cabins and lodging at Fourmile Lake → · more Oregon lake trips
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Fishing Fourmile Lake
Water quality readings over time
2 seasons of samples on record (2024–2025). Calling a direction takes at least 4 years of the same measurement.
Chlorophyll-a
Worsening+0.1 µg/L/yr2 years
Reservoir Info (USACE NID)
Fourmile Lake is a man-made reservoir impounded by the Fourmile Lake Dam (completed 1922), built primarily for flood risk reduction on the Fourmile Creek; rockfill-type dam, 25 ft tall and 660 ft long.
- Surface area
- 962 ac
- Normal storage
- 15,600 ac-ft
- Max storage
- 15,600 ac-ft
- Drainage area
- 10.41 sq mi
- Hazard class
- Low
- Owner
- MEDFORD IRRIGATION DISTRICT
All listed purposes: Flood Risk Reduction;Irrigation.
Source: USACE National Inventory of Dams, NID ID OR00022 · Operator website
Nearby Lakes in Klamath County
Frequently asked questions about Fourmile Lake
Where is Fourmile Lake?
- Fourmile Lake is a lake in Klamath County, Oregon. Its water-quality measurements are published by Oregon DEQ and shown on this page as reported.
What is the water quality of Fourmile Lake?
- Fourmile Lake in Klamath County, Oregon has water-quality measurements published by Oregon DEQ, shown here as reported. Chlorophyll-a (algae): 0.5 µg/L. Surface area: 962 acres.
Is Fourmile Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Fourmile Lake?
- No published bathymetric survey covers Fourmile Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 47 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 962 acres.
Are there boat ramps on Fourmile Lake?
- Fourmile Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Fourmile Lake Campground. Public access is listed as yes.
Can I fish at Fourmile Lake?
- Fourmile Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Oregon's fish and wildlife agency, so check its current regulations before you go.
Are there campgrounds on Fourmile Lake?
- Fourmile Lake has 1 public campground from USGS The National Map within 5 km, including Fourmile Lake Campground. This is a location join, not a booking. Cabins and hotels are listed separately; campsite reservations use the official link when the source provides one.
Explore Fourmile Lake across LakeQuality
Planning a trip around Crater Lake?
Fourmile Lake is about 34 miles from Crater Lake National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Crater Lake →More lakes in Oregon
Other Lakes in Oregon
Oligotrophic Lakes in Oregon
Where this data comes from
8 measurements from 1 monitoring station, 2024–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Department of Environmental Quality - State of Oregon
OREGONDEQ8 samples · 2024–2025
Analytical methods
- 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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory
Public campgrounds from USGS The National Map Structures, within about 3 miles