Siltcoos Lake
Lane County, Oregon3,585 acresView mapDirections
Nutrients and algae run above the regional average.
↓ down from B at the last regrade
- Mesotrophic
- Impaired · Algal growth
- #3 of 3 in the county
- 43 ft max depth
- Public access
- Limited data
Siltcoos Lake in Lane County, Oregon has a water quality grade of D (Nutrient-rich). Chlorophyll-a (algae): 5.4 µg/L. Surface area: 3585 acres.
- Max depth
- ~43 ft est.
- Area
- 3,585 acres
- Type
- Mesotrophic
- Chlorophyll-a
- 5.4 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Siltcoos Lake is a 3,585-acre mesotrophic lake in Lane County, Oregon with an estimated average depth of about 43 feet. Water quality is graded D based on 1 sampling years through 2025. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 4 public boat landings. Compared to the 2 other monitored lakes in Lane County, Siltcoos Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Oregon DEQ, last sampled 2025-10-16. Grade methodology: LakeQuality methodology.
What Siltcoos Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch4 documented ramps
- Camping5 public campgrounds nearby
- Big water3,585 acres
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. Siltcoos Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
No clarity data. Chlorophyll-a 5.4 µg/L. TSI 47. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 5.4 µg/L | Poor |
| Trophic State Index (TSI) | 47 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~43 ft est. |
| Average Depth | ~5 ft est. |
| Surface Area | 3,585 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Oregon has not published bathymetry for Siltcoos Lake.
Lake Size & Watershed
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
- Westlake LandingPublic
- Honeyman Memorial State ParkPublic
- Fish Mill LodgesSemi-private
- Darlings ResortSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Public campgrounds near Siltcoos Lake
- Tyee Campground0.6 km
- Lagoon Campground2.4 km
- Waxmyrtle Campground2.7 km
- Driftwood Ii2.9 km
- Carter Lake (campground & Trailhead)3.9 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
Fishing Siltcoos Lake
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Chlorophyll-a | ↑ Improving | -3.6 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Siltcoos Lake is a man-made reservoir impounded by the Siltcoos Lake (completed 1964), built primarily for other on the Siltcoos River; gravity-type dam, 14 ft tall and 130 ft long.
- Surface area
- 3,585 ac
- Normal storage
- 15,070 ac-ft
- Max storage
- 15,070 ac-ft
- Drainage area
- 50 sq mi
- Hazard class
- Low
- Owner
- INDUSTRIAL HARBOR USA
Source: USACE National Inventory of Dams, NID ID OR00358 · Operator website
EPA Impairment Status
Siltcoos 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_1710020701_02_100176 · Official waterbody report
County Ranking
Ranked #3 of 3 lakes in Lane County
Nearby Lakes in Lane County
Frequently asked questions about Siltcoos Lake
Where is Siltcoos Lake?
- Siltcoos Lake is a lake in Lane County, Oregon. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Siltcoos Lake?
- Siltcoos Lake in Lane County, Oregon has a water quality grade of D (Nutrient-rich). Chlorophyll-a (algae): 5.4 µg/L. Surface area: 3585 acres.
Is Siltcoos Lake safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Siltcoos Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
How deep is Siltcoos Lake?
- No published bathymetric survey covers Siltcoos Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 43 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 3585 acres.
Are there boat ramps on Siltcoos Lake?
- Siltcoos Lake has 4 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Westlake Landing, Honeyman Memorial State Park, Fish Mill Lodges, Darlings Resort. Public access is listed as yes.
Are there campgrounds on Siltcoos Lake?
- Siltcoos Lake has 5 public campgrounds from USGS The National Map within 5 km, including Tyee Campground, Lagoon Campground, Waxmyrtle Campground, Driftwood Ii. 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 Siltcoos Lake across LakeQuality
More Oregon Lake Rankings
Other Grade D Lakes in Oregon
Mesotrophic 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)
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
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