Brook Lake
Grant County, WashingtonView mapDirections
Washington Ecology publishes the water-quality measurements for Brook Lake. Here is what has been measured.
- 38 ft max depth
- Limited data
Brook Lake in Grant County, Washington has water-quality measurements published by Washington Ecology, shown here as reported. Phosphorus: 95 µg/L.
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. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Brook Lake is safe to swim in today is a call for the Washington State Department of Ecology and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Brook Lake
These are the measurements Washington Ecology publishes for Brook Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 95 µg/L. TSI 70.
| 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 | 95µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 70 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Brook Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~38 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
Watershed (drainage) area
2,027 sq mi
HydroLAKES / HydroSHEDS
Surface area
403 acres
HydroLAKES / HydroSHEDS
Shoreline
5.2 mi
HydroLAKES / HydroSHEDS
Elevation
1,234 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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Stays near Brook Lake
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Fishing Brook Lake
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Frequently asked questions about Brook Lake
Where is Brook Lake?
- Brook Lake is a lake in Grant County, Washington. Its water-quality measurements are published by Washington Ecology and shown on this page as reported.
What is the water quality of Brook Lake?
- Brook Lake in Grant County, Washington has water-quality measurements published by Washington Ecology, shown here as reported. Phosphorus: 95 µg/L.
Is Brook Lake safe to swim in?
- Nutrient and algae readings are 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.
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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)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)