Dillon Reservoir
Summit County, Colorado3,300 acresView mapDirections
Nutrients and algae run above the regional average.
↓ down from B at the last regrade
- Mesotrophic
- #3 of 3 in the county
Dillon Reservoir in Summit County, Colorado has a water quality grade of D (Nutrient-rich). Water clarity: 11.6 ft visibility. Phosphorus: 46 µg/L. Chlorophyll-a (algae): 2.8 µg/L. Surface area: 3300 acres.
- Clarity
- 11.6 ft
- Area
- 3,300 acres
- Type
- Mesotrophic
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Stays near Dillon Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Dillon Reservoir in Summit 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Dillon Reservoir are listed below.
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Watch Dillon Reservoir’s letter
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Dillon Reservoir is a 3,300-acre mesotrophic lake in Summit County, Colorado. Water quality is graded D based on 3 sampling years through 2024. Compared to the 2 other monitored lakes in Summit County, Dillon Reservoir ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2024-09-26. Grade methodology: LakeQuality methodology.
What Dillon Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water11.6 ft of visibility
- Camping6 public campgrounds nearby
- Big water3,300 acres
Swimming Safety
Grade onlyElevated nutrients
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 D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Good clarity, visible to about 11.6 ft. Phosphorus 46 µg/L. Chlorophyll-a 2.8 µg/L. TSI 47. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.6 ft | Not graded |
| Phosphorus | 46 µg/L | Poor |
| Chlorophyll-a (Algae) | 2.8 µg/L | Fair |
| Trophic State Index (TSI) | 47 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 3,300 acres |
No bathymetric survey has been published for Dillon Reservoir, so its depth is not documented here.
Recreation & Access
Public campgrounds near Dillon Reservoir
- Windy Point1.2 km
- Prospector1.3 km
- Heaton Bay Cg1.9 km
- Pine Cove Cg1.9 km
- Peak One2.3 km
- Lowry2.4 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 Dillon Reservoir
Reservoir Info (USACE NID)
Dillon Reservoir is a man-made reservoir impounded by the Dillon (completed 1963), built primarily for water supply on the Blue River; earth-type dam, 310 ft tall and 5,900 ft long.
- Surface area
- 3,300 ac
- Normal storage
- 254,036 ac-ft
- Max storage
- 305,000 ac-ft
- Drainage area
- 338 sq mi
- Hazard class
- High
- Owner
- DENVER BOARD OF WATER COMMISSIONERS
All listed purposes: Water Supply;Recreation.
Source: USACE National Inventory of Dams, NID ID CO00875 · Operator website
County Ranking
Ranked #3 of 3 lakes in Summit County
Nearby Lakes in Summit County
Frequently asked questions about Dillon Reservoir
Where is Dillon Reservoir?
- Dillon Reservoir is a lake in Summit County, Colorado. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Dillon Reservoir?
- Dillon Reservoir in Summit County, Colorado has a water quality grade of D (Nutrient-rich). Water clarity: 11.6 ft visibility. Phosphorus: 46 µg/L. Chlorophyll-a (algae): 2.8 µg/L. Surface area: 3300 acres.
Is Dillon Reservoir safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Are there campgrounds on Dillon Reservoir?
- Dillon Reservoir has 6 public campgrounds from USGS The National Map within 5 km, including Windy Point, Prospector, Heaton Bay Cg, Pine Cove Cg. 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 Dillon Reservoir across LakeQuality
Depth, room, public access, and the state wake-sport rules
12.6 mi away · 300 ft
Species activity outlook by water temperature and season
Where to stay at Colorado's top lakes, each with its grade
Moderate nutrients, good water quality
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Other Grade D Lakes in Colorado
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Where this data comes from
30 measurements from 5 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Colorado Dept. of Public Health & Environment-WQCD
21COL001_WQX30 samples · 2020–2024
Analytical methods
- Secchi disk depth measurement
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Nitrogen in Water by Pyrolysis Detection
Monitoring station identifiers (5)
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