Lon Hagler Reservoir
Larimer County, Colorado201 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
↑ up from D at the last regrade
- Mesotrophic
- #1 of 9 in the county
- 16 ft max depth
- Public access
- Limited data
Lon Hagler Reservoir in Larimer County, Colorado has a water quality grade of A (Excellent). Water clarity: 4.6 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 3.8 µg/L. Surface area: 201 acres.
- Clarity
- 4.6 ft
- Max depth
- ~16 ft est.
- Area
- 201 acres
- Type
- Mesotrophic
- Public access
- Yes
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Watch Lon Hagler Reservoir’s letter
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Lon Hagler Reservoir is a 201-acre mesotrophic lake in Larimer County, Colorado with an estimated average depth of about 16 feet. Water quality is graded A based on 3 sampling years through 2021. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 8 other monitored lakes in Larimer County, Lon Hagler Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2021-09-09. Grade methodology: LakeQuality methodology.
What Lon Hagler Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
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 A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
Murky, only visible to about 4.6 ft. Phosphorus 20 µg/L. Chlorophyll-a 3.8 µg/L. TSI 49. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.6 ft | Not graded |
| Phosphorus | 20 µg/L | Good |
| Chlorophyll-a (Algae) | 3.8 µg/L | Good |
| Trophic State Index (TSI) | 49 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~16 ft est. |
| Average Depth | ~12 ft est. |
| Surface Area | 201 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Colorado has not published bathymetry for Lon Hagler 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
- Lon Hagler State Wildlife AreaPublic
- Lon Hagler State Wildlife AreaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Lon Hagler Reservoir
Reservoir Info (USACE NID)
Lon Hagler Reservoir is a man-made reservoir impounded by the Lon Hagler (completed 1967), built primarily for irrigation on the Big Thompson River-Os; earth-type dam, 71 ft tall and 5,085 ft long.
- Surface area
- 201 ac
- Normal storage
- 5,228 ac-ft
- Max storage
- 6,275 ac-ft
- Drainage area
- 0 sq mi
- Hazard class
- High
- Owner
- CONSOLIDATED HOME SUPPLY DITCH & RES. CO (DAVE SCH
All listed purposes: Irrigation;Recreation.
Source: USACE National Inventory of Dams, NID ID CO00165 · Operator website
County Ranking
Ranked #1 of 9 lakes in Larimer County
Nearby Lakes in Larimer County
Frequently asked questions about Lon Hagler Reservoir
Where is Lon Hagler Reservoir?
- Lon Hagler Reservoir is a lake in Larimer County, Colorado. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lon Hagler Reservoir?
- Lon Hagler Reservoir in Larimer County, Colorado has a water quality grade of A (Excellent). Water clarity: 4.6 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 3.8 µg/L. Surface area: 201 acres.
Is Lon Hagler Reservoir safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
How deep is Lon Hagler Reservoir?
- No published bathymetric survey covers Lon Hagler Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 16 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 201 acres.
Are there boat ramps on Lon Hagler Reservoir?
- Lon Hagler Reservoir has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Lon Hagler State Wildlife Area, Lon Hagler State Wildlife Area. Public access is listed as yes.
Explore Lon Hagler Reservoir across LakeQuality
Planning a trip around Rocky Mountain?
Lon Hagler Reservoir is about 29 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 A Lakes in Colorado
Mesotrophic Lakes in Colorado
Where this data comes from
18 measurements from 2 monitoring stations, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Colorado Dept. of Public Health & Environment-WQCD
21COL001_WQX18 samples · 2021
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 (2)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory