Lake Granby Dam Bottom
Grand County, Colorado7,260 acresView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
- Mesotrophic
- #2 of 7 in the county
- Limited data
Lake Granby Dam Bottom in Grand County, Colorado has a water quality grade of B (Good). Phosphorus: 13 µg/L. Surface area: 7260 acres.
- Area
- 7,260 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
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Watch Lake Granby Dam Bottom’s letter
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Lake Granby Dam Bottom is a 7,260-acre mesotrophic lake in Grand County, Colorado. Water quality is graded B based on 2 sampling years through 2020. 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. Grade methodology: LakeQuality methodology.
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 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 B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: B (Good)
No clarity data. Phosphorus 13 µg/L. TSI 41. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 13 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| 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
Fishing Lake Granby Dam Bottom
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +44.08 m/yr | 4 |
| Phosphorus | ↓ Declining | +2.4 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -0.13 µg/L/yr | 3 |
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)
County Ranking
Ranked #2 of 7 lakes in Grand County
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. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Granby Dam Bottom?
- Lake Granby Dam Bottom in Grand County, Colorado has a water quality grade of B (Good). Phosphorus: 13 µg/L. Surface area: 7260 acres.
Is Lake Granby Dam Bottom safe to swim in?
- The B is nutrients and algae, not a swimming clearance. 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 Colorado Lake Rankings
Other Grade B 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)
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
Public campgrounds from USGS The National Map Structures, within about 3 miles