Fall Brook Reservoir
Worcester County, Massachusetts83 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- Impaired · Mercury
- #8 of 24 in the county
- 38 ft max depth
- Limited data
Fall Brook Reservoir in Worcester County, Massachusetts has a water quality grade of A (Excellent). Chlorophyll-a (algae): 1.2 µg/L. Surface area: 83 acres.
- Max depth
- ~38 ft est.
- Area
- 83 acres
- Type
- Oligotrophic
- Chlorophyll-a
- 1.2 µg/L
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Watch Fall Brook Reservoir’s letter
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Fall Brook Reservoir is a 83-acre cold, clear oligotrophic lake in Worcester County, Massachusetts with an estimated average depth of about 38 feet. Water quality is graded A based on 1 sampling years through 2017. 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. 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 A is nutrients and algae, 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.
Water Quality Grade: A (Excellent)
No clarity data. Chlorophyll-a 1.2 µg/L. TSI 32. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 1.2 µg/L | Good |
| Trophic State Index (TSI) | 32 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~38 ft est. |
| Average Depth | ~17 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
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.
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
Source: EPA ATTAINS assessment unit MA81038 · Official waterbody report
County Ranking
Ranked #8 of 24 lakes in Worcester County
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. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Fall Brook Reservoir?
- Fall Brook Reservoir in Worcester County, Massachusetts has a water quality grade of A (Excellent). Chlorophyll-a (algae): 1.2 µg/L. Surface area: 83 acres.
Is Fall Brook Reservoir safe to swim in?
- The A is nutrients and algae, 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.
Explore Fall Brook Reservoir across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Massachusetts's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
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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)
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)