Round Butte Dam Forebay Lake
Jefferson County, Oregon4,000 acresView mapDirections
Nutrients and algae run above the regional average.
- Mesotrophic
- #5 of 14 in the county
Round Butte Dam Forebay Lake in Jefferson County, Oregon has a water quality grade of D (Nutrient-rich). Water clarity: 5.6 ft visibility. Phosphorus: 40 µg/L. Chlorophyll-a (algae): 4.6 µg/L. Surface area: 4000 acres.
- Clarity
- 5.6 ft
- Area
- 4,000 acres
- Type
- Mesotrophic
- Phosphorus
- 40 µg/L
- Chlorophyll-a
- 4.6 µg/L
- Trend
- ↑ Improving
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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 grade measures nutrients and algae, not lodging — cabins and rentals around Round Butte Dam Forebay Lake are listed below.
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Watch Round Butte Dam Forebay Lake’s letter
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Round Butte Dam Forebay Lake is a 4,000-acre mesotrophic lake in Jefferson County, Oregon. Water quality is graded D based on 2 sampling years through 2025. 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. Grade methodology: LakeQuality methodology.
What Round Butte Dam Forebay Lake is good for
From access and monitoring records, not editorial picks.
- Big water4,000 acres
Swimming Safety
Grade onlyElevated nutrients
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 5.6 ft. Phosphorus 40 µg/L. Chlorophyll-a 4.6 µg/L. TSI 52. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.6 ft | Not graded |
| Phosphorus | 40 µg/L | Fair |
| Chlorophyll-a (Algae) | 4.6 µg/L | Poor |
| Trophic State Index (TSI) | 52 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 4,000 acres |
No bathymetric survey has been published for Round Butte Dam Forebay Lake, so its depth is not documented here.
Fishing Round Butte Dam Forebay Lake
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.05 m/yr | 2 |
| Phosphorus | → Stable | 0 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -3.27 µg/L/yr | 2 |
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)
County Ranking
Ranked #5 of 14 lakes in Jefferson County
Nearby Lakes With Higher Grades
Round Butte Dam Forebay Lake holds Grade D. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →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. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Round Butte Dam Forebay Lake?
- Round Butte Dam Forebay Lake in Jefferson County, Oregon has a water quality grade of D (Nutrient-rich). 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?
- The D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Round Butte Dam Forebay Lake across LakeQuality
More Oregon Lake Rankings
Other Grade D Lakes in Oregon
Mesotrophic Lakes in Oregon
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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.