Round Butte Dam Forebay Lake
Jefferson County, Oregon4,000 acresView mapDirections
Oregon DEQ publishes the water-quality measurements for Round Butte Dam Forebay Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Algal growth
Round Butte Dam Forebay Lake in Jefferson County, Oregon has water-quality measurements published by Oregon DEQ, shown here as reported. Water clarity: 5.6 ft visibility. Phosphorus: 40 µg/L. Chlorophyll-a (algae): 4.6 µg/L. Surface area: 4000 acres.
Round Butte Dam Forebay Lake is a 4,000-acre mesotrophic lake in Jefferson County, Oregon. Overall water quality is improving over recent sampling years. Compared to the 13 other monitored lakes in Jefferson County, Round Butte Dam Forebay Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Oregon DEQ, last sampled 2025-09-09. Methodology: how these readings are compared.
What Round Butte Dam Forebay Lake is good for
From access and monitoring records, not editorial picks.
- Big water4,000 acres
Swimming conditions
Readings onlyElevated nutrients
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. Round Butte Dam Forebay Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, hydrologic alteration, pH / acidity. Check local advisories before you swim.
Whether Round Butte Dam Forebay 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 Round Butte Dam Forebay Lake
These are the measurements Oregon DEQ publishes for Round Butte Dam Forebay 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 5.6 ft. Phosphorus 40 µg/L. Chlorophyll-a 4.6 µg/L. TSI 52.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 40µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 4.6µg/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. | 52 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Round Butte Dam Forebay Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
4,000 acres
No bathymetric survey has been published for Round Butte Dam Forebay Lake, so its depth is not documented here.
Stays via Stay22
Stays near Round Butte Dam Forebay Lake
Compare lakeside cabins, hotels, and vacation rentals near Round Butte Dam Forebay Lake in Jefferson 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 Round Butte Dam Forebay Lake are listed below.
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Fishing Round Butte Dam Forebay Lake
Water quality readings over time
2 seasons of samples on record (2021–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Improving2 years
Phosphorus
Stable0 µg/L/yr2 years
Chlorophyll-a
Improving-3.27 µg/L/yr2 years
Reservoir Info (USACE NID)
Round Butte Dam Forebay Lake is a man-made reservoir impounded by the Round Butte (completed 1964), built primarily for hydroelectric on the Deschutes River; rockfill-type dam, 440 ft tall and 1,450 ft long.
- Surface area
- 4,000 ac
- Normal storage
- 535,000 ac-ft
- Max storage
- 535,000 ac-ft
- Drainage area
- 7,514 sq mi
- Hazard class
- High
- Owner
- Portland General Electric Company
All listed purposes: Hydroelectric;Recreation.
Source: USACE National Inventory of Dams, NID ID OR00549 · Operator website · Matched by proximity (0.62 km)
EPA Impairment Status
Round Butte Dam Forebay 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: Aquatic life, Other.
Source: EPA ATTAINS assessment unit OR_LK_1707030111_02_100151 · Official waterbody report
Nearby Lakes in Jefferson County
Frequently asked questions about Round Butte Dam Forebay Lake
Where is Round Butte Dam Forebay Lake?
- Round Butte Dam Forebay Lake is a lake in Jefferson County, Oregon. Its water-quality measurements are published by Oregon DEQ and shown on this page as reported.
What is the water quality of Round Butte Dam Forebay Lake?
- Round Butte Dam Forebay Lake in Jefferson County, Oregon has water-quality measurements published by Oregon DEQ, shown here as reported. Water clarity: 5.6 ft visibility. Phosphorus: 40 µg/L. Chlorophyll-a (algae): 4.6 µg/L. Surface area: 4000 acres.
Is Round Butte Dam Forebay Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Round Butte Dam Forebay Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, hydrologic alteration, pH / acidity. Check local advisories before you swim.
Explore Round Butte Dam Forebay Lake across LakeQuality
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Where this data comes from
91 measurements from 1 monitoring station, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Department of Environmental Quality - State of Oregon
OREGONDEQ91 samples · 2021–2025
Analytical methods
- 2012 National Lakes Assessment Field Operations Manual
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 10200 H ~ Chlorophyll a-b-c Determination
- 2130 B ~ Nephelometric Method
- Standard Test Method for Determination of Turbidity Above 1 Turbidity Unit (TU) in Static Mode
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