Fall Brook Reservoir
Worcester County, Massachusetts83 acresView mapDirections
MassDEP publishes the water-quality measurements for Fall Brook Reservoir. Here is what has been measured.
- Oligotrophic
- Impaired · Mercury
- 38 ft max depth
- Limited data
Fall Brook Reservoir in Worcester County, Massachusetts has water-quality measurements published by MassDEP, shown here as reported. Chlorophyll-a (algae): 1.2 µg/L. Surface area: 83 acres.
Fall Brook Reservoir is a 83-acre cold, clear oligotrophic lake in Worcester County, Massachusetts with an estimated average depth of about 38 feet. Compared to the 23 other monitored lakes in Worcester County, Fall Brook Reservoir ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, MassDEP, last sampled 2017-09-19. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
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. Fall Brook Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Whether Fall Brook Reservoir is safe to swim in today is a call for the Massachusetts Department of Environmental Protection and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Fall Brook Reservoir
These are the measurements MassDEP publishes for Fall Brook Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Chlorophyll-a 1.2 µg/L. TSI 32.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | 1.2µg/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. | 32 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Fall Brook Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~38 ft est.
Surface area
83 acres
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Massachusetts has not published bathymetry for Fall Brook Reservoir.
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Shoreline
1.7 mi
HydroLAKES / HydroSHEDS
Elevation
653 ft
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.
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Fishing Fall Brook Reservoir
Reservoir Info (USACE NID)
Fall Brook Reservoir is a man-made reservoir impounded by the Fall Brook Reservoir Dam and Dike (completed 1896), built primarily for water supply on the Fall Brook; earth-type dam, 37 ft tall and 1,400 ft long.
- Surface area
- 83 ac
- Normal storage
- 1,290 ac-ft
- Max storage
- 1,750 ac-ft
- Drainage area
- 1.3 sq mi
- Hazard class
- High
- Owner
- City of Leominster
Source: USACE National Inventory of Dams, NID ID MA00869 · Operator website · Matched by proximity (0.44 km)
EPA Impairment Status
Fall Brook Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Fish consumption.
Source: EPA ATTAINS assessment unit MA81038 · Official waterbody report
Nearby Lakes in Worcester County
Frequently asked questions about Fall Brook Reservoir
Where is Fall Brook Reservoir?
- Fall Brook Reservoir is a lake in Worcester County, Massachusetts. Its water-quality measurements are published by MassDEP and shown on this page as reported.
What is the water quality of Fall Brook Reservoir?
- Fall Brook Reservoir in Worcester County, Massachusetts has water-quality measurements published by MassDEP, shown here as reported. Chlorophyll-a (algae): 1.2 µg/L. Surface area: 83 acres.
Is Fall Brook Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Fall Brook Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
How deep is Fall Brook Reservoir?
- No published bathymetric survey covers Fall Brook Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 38 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 83 acres.
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Where this data comes from
3 measurements from 1 monitoring station, 2017. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Massachusetts Department of Environmental Protection (MassDEP)
MASSDEP3 samples · 2017
Analytical methods
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)