Billy Chinook Reservoir
Jefferson County, Oregon4,000 acresView mapDirections
Nutrients and algae sit mid-range for this region.
↓ down from B at the last regrade
- Mesotrophic
- Impaired · Algal growth
- #1 of 14 in the county
Billy Chinook Reservoir in Jefferson County, Oregon has a water quality grade of C (Fair). Water clarity: 4.4 ft visibility. Phosphorus: 70 µg/L. Chlorophyll-a (algae): 2.2 µg/L. Surface area: 4000 acres.
- Clarity
- 4.4 ft
- Area
- 4,000 acres
- Type
- Mesotrophic
- Phosphorus
- 70 µg/L
- Chlorophyll-a
- 2.2 µg/L
- Trend
- ↑ Improving
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Watch Billy Chinook Reservoir’s letter
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Billy Chinook Reservoir is a 4,000-acre mesotrophic lake in Jefferson County, Oregon. Water quality is graded C based on 1 sampling years through 2025. Overall water quality is improving over recent sampling years. Compared to the 13 other monitored lakes in Jefferson County, Billy Chinook Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Oregon DEQ, last sampled 2025-09-09. Grade methodology: LakeQuality methodology.
What Billy Chinook Reservoir is good for
From access and monitoring records, not editorial picks.
- Big water4,000 acres
Swimming Safety
Grade onlyModerate
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 C is nutrients and algae, not a swimming clearance. Billy Chinook Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, hydrologic alteration, pH / acidity. Check local advisories before you swim.
Water Quality Grade: C (Fair)
Murky, only visible to about 4.4 ft. Phosphorus 70 µg/L. Chlorophyll-a 2.2 µg/L. TSI 53. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.4 ft | Not graded |
| Phosphorus | 70 µg/L | Not graded |
| Chlorophyll-a (Algae) | 2.2 µg/L | Fair |
| Trophic State Index (TSI) | 53 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 4,000 acres |
No bathymetric survey has been published for Billy Chinook Reservoir, so its depth is not documented here.
Fishing Billy Chinook Reservoir
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.063 m/yr | 2 |
| Phosphorus | ↑ Improving | -2.5 µg/L/yr | 2 |
| Chlorophyll-a | ↓ Declining | +2.63 µg/L/yr | 3 |
Reservoir Info (USACE NID)
Billy Chinook Reservoir 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
EPA Impairment Status
Billy Chinook Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit OR_LK_1707030111_02_100151 · Official waterbody report
County Ranking
Ranked #1 of 14 lakes in Jefferson County
Nearby Lakes in Jefferson County
Frequently asked questions about Billy Chinook Reservoir
Where is Billy Chinook Reservoir?
- Billy Chinook Reservoir is a lake in Jefferson County, Oregon. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Billy Chinook Reservoir?
- Billy Chinook Reservoir in Jefferson County, Oregon has a water quality grade of C (Fair). Water clarity: 4.4 ft visibility. Phosphorus: 70 µg/L. Chlorophyll-a (algae): 2.2 µg/L. Surface area: 4000 acres.
Is Billy Chinook Reservoir safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Billy Chinook Reservoir 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 Billy Chinook Reservoir across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at Oregon's top lakes, each with its grade
Moderate nutrients, good water quality
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Where this data comes from
105 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
OREGONDEQ105 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.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database