Brook Lake
Grant County, WashingtonView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- 38 ft max depth
- Limited data
Brook Lake in Grant County, Washington is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 95 µg/L.
- Max depth
- ~38 ft est.
- Phosphorus
- 95 µg/L
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Watch Brook Lake’s letter
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Why Brook Lake has no grade
We grade a lake only when the monitoring record supports a letter: 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 Brook Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded phosphorus, but not water clarity and algae (chlorophyll-a).
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 WA Ecology and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Brook Lake is a lake in Grant County, Washington with an estimated average depth of about 38 feet.
Source: EPA Water Quality Portal sampling records, WA Ecology, last sampled 2021-10-28. Grade methodology: LakeQuality methodology.
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Brook Lake
These readings exist but are not enough for an A–F grade — see why.
No clarity data. Phosphorus 95 µg/L. TSI 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 95 µg/L | Not graded |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 70 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~38 ft est. |
| Average Depth | ~23 ft est. |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Washington has not published bathymetry for Brook 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.
Fishing Brook Lake
Graded lakes near Brook Lake
Brook Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Grant County
Frequently asked questions about Brook Lake
Where is Brook Lake?
- Brook Lake is a lake in Grant County, Washington. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Brook Lake?
- Brook Lake in Grant County, Washington is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 95 µg/L.
Is Brook Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
How deep is Brook Lake?
- No published bathymetric survey covers Brook Lake, 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.
Explore Brook Lake across LakeQuality
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Where this data comes from
4 measurements from 1 monitoring station, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Washington Water Science Center
USGS-WA4 samples · 2021
Analytical methods
- Nutrients, wu, WCA,persulfate,CF
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
Lake size & watershed from HydroLAKES (HydroSHEDS)