Willow Creek Reservoir
Grand County, Colorado303 acresView mapDirections
Nutrients and algae sit mid-range for this region.
- Mesotrophic
- #3 of 7 in the county
- 20 ft max depth
Willow Creek Reservoir in Grand County, Colorado has a water quality grade of C (Fair). Water clarity: 3.9 ft visibility. Phosphorus: 75.5 µg/L. Chlorophyll-a (algae): 2.4 µg/L. Surface area: 303 acres.
- Clarity
- 3.9 ft
- Max depth
- ~20 ft est.
- Area
- 303 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
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Watch Willow Creek Reservoir’s letter
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Willow Creek Reservoir is a 303-acre mesotrophic lake in Grand County, Colorado with an estimated average depth of about 20 feet. Water quality is graded C based on 1 sampling years through 2024. Overall water quality is improving over recent sampling years. Compared to the 6 other monitored lakes in Grand County, Willow Creek Reservoir ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2024-01-29. Grade methodology: LakeQuality methodology.
What Willow Creek Reservoir is good for
From access and monitoring records, not editorial picks.
- Camping1 public campground nearby
Swimming Safety
Grade onlyModerate
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 C is nutrients and algae, not a swimming clearance. Willow Creek Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury). Check local advisories before you swim.
Water Quality Grade: C (Fair)
Murky, only visible to about 3.9 ft. Phosphorus 75.5 µg/L. Chlorophyll-a 2.4 µg/L. TSI 54. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | Not graded |
| Phosphorus | 75.5 µg/L | Not graded |
| Chlorophyll-a (Algae) | 2.4 µg/L | Fair |
| Trophic State Index (TSI) | 54 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~20 ft est. |
| Surface Area | 303 acres |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Colorado has not published bathymetry for Willow Creek Reservoir.
Lake Size & Watershed
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.
Recreation & Access
Public campgrounds near Willow Creek Reservoir
- Willow Creek1.1 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 Willow Creek Reservoir
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +19.625 m/yr | 3 |
| Phosphorus | ↓ Declining | +5.5 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -1 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Willow Creek Reservoir is a man-made reservoir impounded by the Willow Creek Bor CO Dam (completed 1953), built primarily for irrigation on the Willow Creek; earth-type dam, 127 ft tall and 1,100 ft long.
- Surface area
- 303 ac
- Normal storage
- 10,553 ac-ft
- Max storage
- 11,177 ac-ft
- Drainage area
- 127 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Irrigation;Recreation.
Source: USACE National Inventory of Dams, NID ID CO01670 · Operator website · Matched by proximity (0.16 km)
EPA Impairment Status
Willow Creek Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit COUCUC12_D · Official waterbody report
County Ranking
Ranked #3 of 7 lakes in Grand County
Nearby Lakes in Grand County
Frequently asked questions about Willow Creek Reservoir
Where is Willow Creek Reservoir?
- Willow Creek Reservoir is a lake in Grand County, Colorado. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Willow Creek Reservoir?
- Willow Creek Reservoir in Grand County, Colorado has a water quality grade of C (Fair). Water clarity: 3.9 ft visibility. Phosphorus: 75.5 µg/L. Chlorophyll-a (algae): 2.4 µg/L. Surface area: 303 acres.
Is Willow Creek Reservoir safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Willow Creek Reservoir 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 Willow Creek Reservoir?
- No published bathymetric survey covers Willow Creek Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 20 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 303 acres.
Are there campgrounds on Willow Creek Reservoir?
- Willow Creek Reservoir has 1 public campground from USGS The National Map within 5 km, including Willow Creek. 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 Willow Creek Reservoir across LakeQuality
10.3 mi away · recorded at 111°F
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
Colorado's cleanest and most-polluted lakes, ranked
Planning a trip around Rocky Mountain?
Willow Creek Reservoir is about 19 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 C Lakes in Colorado
Mesotrophic Lakes in Colorado
Where this data comes from
1,280 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Colorado Water Science Center
USGS-CO1,280 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 (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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Public campgrounds from USGS The National Map Structures, within about 3 miles