Grand Lake
Grand County, ColoradoView mapDirections
Colorado WQCD publishes the water-quality measurements for Grand Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Metals (other than mercury)
- 25 ft max depth
Grand Lake in Grand County, Colorado has water-quality measurements published by Colorado WQCD, shown here as reported. Water clarity: 8.7 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 2.7 µg/L.
Grand Lake is a mesotrophic lake in Grand County, Colorado with an estimated average depth of about 25 feet. Overall water quality is improving over recent sampling years. Compared to the 6 other monitored lakes in Grand County, Grand Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2024-01-30. Methodology: how these readings are compared.
If you are planning to stay, you can search lake houses and cabins around Grand Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
Swimming conditions
Readings onlyModerate 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. Grand Lake is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury). Check local advisories before you swim.
Whether Grand Lake is safe to swim in today is a call for the Water Quality Control Division of the Colorado Department of Public Health and Environment and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Grand Lake
These are the measurements Colorado WQCD publishes for Grand Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 8.7 ft. Phosphorus 14 µg/L. Chlorophyll-a 2.7 µg/L. TSI 43.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 8.7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 14µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.7µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 43 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Grand Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~25 ft est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Colorado has not published bathymetry for Grand Lake.
Lake Size & Watershed
Watershed (drainage) area
76 sq mi
HydroLAKES / HydroSHEDS
Surface area
460 acres
HydroLAKES / HydroSHEDS
Shoreline
3.8 mi
HydroLAKES / HydroSHEDS
Elevation
8,386 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.
Stays via Stay22
Stays near Grand Lake
Compare lakeside cabins, hotels, and vacation rentals near Grand Lake in Grand County, Colorado — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
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Fishing Grand Lake
Water quality readings over time
3 seasons of samples on record (2021–2023). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Improving3 years
Phosphorus
Improving-1 µg/L/yr3 years
Chlorophyll-a
Improving-0.3 µg/L/yr2 years
EPA Impairment Status
Grand Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Drinking water.
Source: EPA ATTAINS assessment unit COUCUC12_E · Official waterbody report
Nearby Lakes in Grand County
Frequently asked questions about Grand Lake
Where is Grand Lake?
- Grand Lake is a lake in Grand County, Colorado. Its water-quality measurements are published by Colorado WQCD and shown on this page as reported.
What is the water quality of Grand Lake?
- Grand Lake in Grand County, Colorado has water-quality measurements published by Colorado WQCD, shown here as reported. Water clarity: 8.7 ft visibility. Phosphorus: 14 µg/L. Chlorophyll-a (algae): 2.7 µg/L.
Is Grand Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Grand Lake is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury). Check local advisories before you swim.
How deep is Grand Lake?
- No published bathymetric survey covers Grand Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 25 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Grand Lake across LakeQuality
Planning a trip around Rocky Mountain?
Grand Lake is about 10 miles from Rocky Mountain National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Rocky Mountain →More lakes in Colorado
Other Lakes in Colorado
Mesotrophic Lakes in Colorado
Where this data comes from
3,673 measurements from 2 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Colorado Water Science Center
USGS-CO3,673 samples · 2020–2024
Analytical methods
- Secchi disk method
- Phosphorus, LL,wu,persulfate(CO)
- YSI EXO, 470/685/40,S bacillaris
- Plant pigments, sonication & 445
- YSI EXO turbidity sensor, FNU
Monitoring station identifiers (2)
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)