Lake Granby Dam Bottom
Grand County, Colorado7,260 acresView mapDirections
Colorado WQCD publishes the water-quality measurements for Lake Granby Dam Bottom. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- Limited data
Lake Granby Dam Bottom in Grand County, Colorado has water-quality measurements published by Colorado WQCD, shown here as reported. Phosphorus: 13 µg/L. Surface area: 7260 acres.
Lake Granby Dam Bottom is a 7,260-acre mesotrophic lake in Grand County, Colorado. Overall water quality is improving over recent sampling years. Compared to the 6 other monitored lakes in Grand County, Lake Granby Dam Bottom ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2020-09-16. Methodology: how these readings are compared.
What Lake Granby Dam Bottom is good for
From access and monitoring records, not editorial picks.
- Camping2 public campgrounds nearby
- Big water7,260 acres
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. Lake Granby Dam Bottom is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury). Check local advisories before you swim.
Whether Lake Granby Dam Bottom 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 Lake Granby Dam Bottom
These are the measurements Colorado WQCD publishes for Lake Granby Dam Bottom, 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 13 µg/L. TSI 41.
| 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 | 13µg/L | Good GoodFairPoor |
| 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. | 41 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Lake Granby Dam Bottom
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
7,260 acres
No bathymetric survey has been published for Lake Granby Dam Bottom, so its depth is not documented here.
Recreation & Access
Public campgrounds near Lake Granby Dam Bottom
- Sunset Point0.8 km
- Stillwater3.8 km
Nearest public campgrounds in the USGS National Map inventory, within about 3 miles. An empty list means USGS records no campground that close, which is not the same as camping being unavailable. Where the source gives an official reservation link, it is used; the cabin and hotel search does not cover campsites. More camping lakes
Stays via Stay22
Stays near Lake Granby Dam Bottom
Compare lakeside cabins, hotels, and vacation rentals near Lake Granby Dam Bottom 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.
Top-rated places to stay near Lake Granby Dam Bottom
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Fishing Lake Granby Dam Bottom
Water Quality Trend: Improving
Based on 4 years of monitoring (2020–2023).
Water clarity
Improving4 years
Phosphorus
Worsening+2.4 µg/L/yr4 years
Chlorophyll-a
Improving-0.13 µg/L/yr3 years
Reservoir Info (USACE NID)
Lake Granby Dam Bottom is a man-made reservoir impounded by the Granby Dam (completed 1950), built primarily for hydroelectric on the Colorado River; earth-type dam, 298 ft tall and 861 ft long.
- Surface area
- 7,260 ac
- Normal storage
- 539,760 ac-ft
- Max storage
- 539,760 ac-ft
- Drainage area
- 311.95 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Hydroelectric;Irrigation.
Source: USACE National Inventory of Dams, NID ID CO01656 · Operator website · Matched by proximity (0.14 km)
EPA Impairment Status
Lake Granby Dam Bottom 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, Aquatic life.
Source: EPA ATTAINS assessment unit COUCUC12_C · Official waterbody report
Nearby Lakes in Grand County
Frequently asked questions about Lake Granby Dam Bottom
Where is Lake Granby Dam Bottom?
- Lake Granby Dam Bottom 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 Lake Granby Dam Bottom?
- Lake Granby Dam Bottom in Grand County, Colorado has water-quality measurements published by Colorado WQCD, shown here as reported. Phosphorus: 13 µg/L. Surface area: 7260 acres.
Is Lake Granby Dam Bottom safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake Granby Dam Bottom is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, metals (other than mercury). Check local advisories before you swim.
Are there campgrounds on Lake Granby Dam Bottom?
- Lake Granby Dam Bottom has 2 public campgrounds from USGS The National Map within 5 km, including Sunset Point, Stillwater. This is a location join, not a booking. Cabins and hotels are listed separately; campsite reservations use the official link when the source provides one.
Explore Lake Granby Dam Bottom across LakeQuality
Planning a trip around Rocky Mountain?
Lake Granby Dam Bottom is about 17 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
6 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Colorado Dept. of Public Health & Environment-WQCD
21COL001_WQX6 samples · 2020
Analytical methods
- Phosphorus by Colorimetry
- Nitrogen in Water by Pyrolysis Detection
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
Public campgrounds from USGS The National Map Structures, within about 3 miles