Dillon Reservoir
Summit County, Colorado3,300 acresView mapDirections
Colorado WQCD publishes the water-quality measurements for Dillon Reservoir. Here is what has been measured.
- Mesotrophic
Dillon Reservoir in Summit County, Colorado has water-quality measurements published by Colorado WQCD, shown here as reported. Water clarity: 11.6 ft visibility. Phosphorus: 46 µg/L. Chlorophyll-a (algae): 2.8 µg/L. Surface area: 3300 acres.
Dillon Reservoir is a 3,300-acre mesotrophic lake in Summit County, Colorado. 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. Methodology: how these readings are compared.
Dillon Reservoir covers about 3,300 acres in Summit County. Vrbo is where to look for cabins and lake homes around Dillon Reservoir, and Booking.com and Expedia search hotels near the lake for your dates.
What Dillon Reservoir is good for
From access and monitoring records, not editorial picks.
- Clear water11.6 ft of visibility
- Camping7 public campgrounds nearby
- Big water3,300 acres
Swimming conditions
Readings onlyElevated nutrients
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. Check local advisories before you swim.
Whether Dillon Reservoir 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 Dillon Reservoir
These are the measurements Colorado WQCD publishes for Dillon Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 11.6 ft. Phosphorus 46 µg/L. Chlorophyll-a 2.8 µg/L. TSI 47.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 11.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 46µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 2.8µg/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. | 47 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Dillon Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
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
- Windy Point Group (co)1.2 kmReserve
- Prospector1.3 km
- Lowry Campground1.8 kmReserve
- Heaton Bay Cg1.9 km
- Pine Cove Cg1.9 km
- Peak One2.2 kmReserve
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 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Dillon Reservoir are listed below.
Top-rated places to stay near Dillon Reservoir
Prices for Oct 23–25, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
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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
Nearby Lakes in Summit County
Frequently asked questions about Dillon Reservoir
Where is Dillon Reservoir?
- Dillon Reservoir is a lake in Summit County, Colorado. Its water-quality measurements are published by Colorado WQCD and shown on this page as reported.
What is the water quality of Dillon Reservoir?
- Dillon Reservoir in Summit County, Colorado has water-quality measurements published by Colorado WQCD, shown here as reported. 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?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Are there campgrounds on Dillon Reservoir?
- Dillon Reservoir has 7 public campgrounds from USGS The National Map within 5 km, including Windy Point, Windy Point Group (co), Prospector, Lowry Campground. 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 readings
Colorado's cleanest lakes, ranked on agency measurements
More lakes in Colorado
Other Lakes in Colorado
Mesotrophic Lakes in Colorado
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)
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
Public campgrounds from USGS The National Map Structures, within about 3 miles