Grand Falls Flowage Lake
Washington County, Maine18,040 acresView mapDirections
Maine DEP publishes the water-quality measurements for Grand Falls Flowage Lake. Here is what has been measured.
- Mesotrophic
- Public access
Grand Falls Flowage Lake in Washington County, Maine has water-quality measurements published by Maine DEP, shown here as reported. Water clarity: 14 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 3.7 µg/L. Surface area: 18040 acres.
Grand Falls Flowage Lake is a 18,040-acre mesotrophic lake in Washington County, Maine. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 10 other monitored lakes in Washington County, Grand Falls Flowage Lake ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-09-25. Methodology: how these readings are compared.
What Grand Falls Flowage Lake is good for
From access and monitoring records, not editorial picks.
- Clear water14 ft of visibility
- Boat launch1 documented ramp
- Big water18,040 acres
Swimming conditions
Readings onlyLow algae
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Grand Falls Flowage Lake is safe to swim in today is a call for the Maine Department of Environmental Protection and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Grand Falls Flowage Lake
These are the measurements Maine DEP publishes for Grand Falls Flowage Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 14 ft. Phosphorus 10 µg/L. Chlorophyll-a 3.7 µg/L. TSI 40.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 14ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 10µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 3.7µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 40 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Grand Falls Flowage Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
18,040 acres
Public access
Yes
Listed by Maine DEP
No bathymetric survey has been published for Grand Falls Flowage Lake, so its depth is not documented here.
Recreation & Access
- Grand Falls FlowagePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
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Fishing Grand Falls Flowage Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Stable+0.09 µg/L/yr6 years
Chlorophyll-a
Worsening+0.27 µg/L/yr6 years
Reservoir Info (USACE NID)
Grand Falls Flowage Lake is a man-made reservoir impounded by the Grand Falls (completed 1915), built primarily for hydroelectric on the Saint Croix; concrete-type dam, 50 ft tall and 1,135 ft long.
- Surface area
- 18,040 ac
- Normal storage
- 88,000 ac-ft
- Max storage
- 149,600 ac-ft
- Drainage area
- 1,320 sq mi
- Hazard class
- High
- Owner
- Woodland Pulp LLC
Source: USACE National Inventory of Dams, NID ID ME00219 · Operator website
Nearby Lakes in Washington County
Frequently asked questions about Grand Falls Flowage Lake
Where is Grand Falls Flowage Lake?
- Grand Falls Flowage Lake is a lake in Washington County, Maine. Its water-quality measurements are published by Maine DEP and shown on this page as reported.
What is the water quality of Grand Falls Flowage Lake?
- Grand Falls Flowage Lake in Washington County, Maine has water-quality measurements published by Maine DEP, shown here as reported. Water clarity: 14 ft visibility. Phosphorus: 10 µg/L. Chlorophyll-a (algae): 3.7 µg/L. Surface area: 18040 acres.
Is Grand Falls Flowage Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Grand Falls Flowage Lake?
- Grand Falls Flowage Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Grand Falls Flowage. Public access is listed as yes.
Can I fish at Grand Falls Flowage Lake?
- Grand Falls Flowage Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Maine's fish and wildlife agency, so check its current regulations before you go.
Explore Grand Falls Flowage Lake across LakeQuality
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Mesotrophic Lakes in Maine
Where this data comes from
96 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Submitting organization not recorded for these samples96 samples · 2020–2025
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Named boat-access points from the USGS National Boat Ramps inventory