Folsom Lake
Folsom Lake in Placer County, California is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 4.5 µg/L. Chlorophyll-a (algae): 1 µg/L. Surface area: 11180 acres.
- Area
- 11,180 acres
- Public access
- Yes
Why Folsom Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Folsom Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded phosphorus and algae (chlorophyll-a), but not water clarity.
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by your state environmental agency and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Folsom Lake is a 11,180-acre lake in Placer County, California. Limited fish-species data available. Public access is available with 2 public boat landings.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-08-07. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Folsom Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
No clarity data. Phosphorus level: 4.5 µg/L. Chlorophyll-a: 1 µg/L. Trophic State Index: 28.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 4.5 µg/L | Not graded |
| Chlorophyll-a (Algae) | 1 µg/L | Not graded |
| Trophic State Index (TSI) | 28 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Folsom Lake
Compare lakeside cabins, hotels, and vacation rentals near Folsom Lake in Placer County, California — 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.
Top-rated places to stay near Folsom Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 11,180 acres |
| Public Access | Yes |
No bathymetric survey has been published for Folsom Lake, so its depth is not documented here.
Recreation & Access
- Folsom Lake State Recreation AreaPublic
- Folsom Lake State Recreation Area (Beal's Point)Public
Named access points from the USGS National Boat Ramps inventory, snapped within 5 km. More lakes with boat ramps
Fishing Folsom Lake
Reservoir Info (USACE NID)
Folsom Lake is a man-made reservoir impounded by the Folsom Dike 4 (completed 1956), built primarily for flood risk reduction on the American River; earth-type dam, 30 ft tall and 1,420 ft long.
- Surface area
- 11,180 ac
- Max storage
- 976,955 ac-ft
- Drainage area
- 1,570 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Flood Risk Reduction;Irrigation;Recreation;Hydroelectric;Water Supply.
Source: USACE National Inventory of Dams, NID ID CA10148 · Operator website
Nearby Lakes in Placer County
Frequently asked questions about Folsom Lake
Where is Folsom Lake?
- Folsom Lake is a lake in Placer County, California. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.
What is the water quality grade for Folsom Lake?
- Folsom Lake in Placer County, California is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 4.5 µg/L. Chlorophyll-a (algae): 1 µg/L. Surface area: 11180 acres.
Is Folsom Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Folsom Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Algae concentration (chlorophyll-a) is 1 µg/L. Always check local health department advisories before swimming.
Are there boat ramps on Folsom Lake?
- Folsom Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Folsom Lake State Recreation Area, Folsom Lake State Recreation Area (Beal's Point). Public access is listed as yes.
Explore Folsom Lake across LakeGrade
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Where this data comes from
4 measurements from 2 monitoring stations, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- USGS California Water Science Center
USGS-CA4 samples · 2023
Analytical methods
- Nutrients, wu, persulfate, color
- Pigments, algae, EPA445.0 w/ACTN
Monitoring station identifiers (2)
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
Named boat-access points from the USGS National Boat Ramps inventory