Crooked River Arm Lake
Jefferson County, OregonView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- Impaired · Algal growth
- #7 of 14 in the county
- Limited data
Crooked River Arm Lake in Jefferson County, Oregon has a water quality grade of D (Nutrient-rich). Phosphorus: 60 µg/L. Chlorophyll-a (algae): 24.6 µg/L.
- Type
- Eutrophic
- Phosphorus
- 60 µg/L
- Chlorophyll-a
- 24.6 µg/L
Stays via Stay22
Stays near Crooked River Arm Lake
Compare lakeside cabins, hotels, and vacation rentals near Crooked River Arm 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 Crooked River Arm Lake are listed below.
Top-rated places to stay near Crooked River Arm Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
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Watch Crooked River Arm Lake’s letter
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Crooked River Arm Lake is a productive, nutrient-rich eutrophic lake in Jefferson County, Oregon. Water quality is graded D based on 2 sampling years through 2021. Compared to the 13 other monitored lakes in Jefferson County, Crooked River Arm Lake ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, Oregon DEQ, last sampled 2021-10-20. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLimited data
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. Crooked River Arm Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, hydrologic alteration. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
No clarity data. Phosphorus 60 µg/L. Chlorophyll-a 24.6 µg/L. TSI 63. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 60 µg/L | Poor |
| Chlorophyll-a (Algae) | 24.6 µg/L | Poor |
| Trophic State Index (TSI) | 63 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Fishing Crooked River Arm Lake
EPA Impairment Status
Crooked River Arm Lake 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_1707030511_02_100117 · Official waterbody report · Matched by proximity (1.28 km)
County Ranking
Ranked #7 of 14 lakes in Jefferson County
Nearby Lakes With Higher Grades
Crooked River Arm Lake holds Grade D. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Jefferson County
Frequently asked questions about Crooked River Arm Lake
Where is Crooked River Arm Lake?
- Crooked River Arm 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 Crooked River Arm Lake?
- Crooked River Arm Lake in Jefferson County, Oregon has a water quality grade of D (Nutrient-rich). Phosphorus: 60 µg/L. Chlorophyll-a (algae): 24.6 µg/L.
Is Crooked River Arm Lake safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Crooked River Arm Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, hydrologic alteration. Check local advisories before you swim.
Explore Crooked River Arm Lake across LakeQuality
More Oregon Lake Rankings
Other Grade D Lakes in Oregon
Eutrophic Lakes in Oregon
Where this data comes from
30 measurements from 1 monitoring station, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Department of Environmental Quality - State of Oregon
OREGONDEQ30 samples · 2021
Analytical methods
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 10200 H ~ Chlorophyll a-b-c Determination
- 2130 B ~ Nephelometric Method
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