Lake Isabel
Custer County, Colorado35 acresView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- 12 ft max depth
- Limited data
Lake Isabel in Custer County, Colorado is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 5.9 ft visibility. Phosphorus: 232 µg/L. Chlorophyll-a (algae): 0.8 µg/L. Surface area: 35 acres.
- Clarity
- 5.9 ft
- Max depth
- ~12 ft est.
- Area
- 35 acres
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Stays near Lake Isabel
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Watch Lake Isabel’s letter
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Why Lake Isabel has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Lake Isabel, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by CDPHE and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Lake Isabel is a 35-acre lake in Custer County, Colorado with an estimated average depth of about 12 feet.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2022-07-13. Grade methodology: LakeQuality methodology.
What Lake Isabel is good for
From access and monitoring records, not editorial picks.
- Camping5 public campgrounds nearby
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Lake Isabel
These readings exist but are not enough for an A–F grade — see why.
Murky, only visible to about 5.9 ft. Phosphorus 232 µg/L. Chlorophyll-a 0.8 µg/L. TSI 54.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.9 ft | Not graded |
| Phosphorus | 232 µg/L | Not graded |
| Chlorophyll-a (Algae) | 0.8 µg/L | Not graded |
| Trophic State Index (TSI) | 54 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~12 ft est. |
| Surface Area | 35 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 Lake Isabel.
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 Lake Isabel
- Southside0.4 km
- La Vista0.7 km
- St. Charles1.5 km
- Ponderosa1.9 km
- Spruce2.2 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 Isabel
Reservoir Info (USACE NID)
Lake Isabel is a man-made reservoir impounded by the Lake Isabel (completed 1937), built primarily for recreation on the St Charles River; earth-type dam, 98 ft tall and 680 ft long.
- Surface area
- 35 ac
- Normal storage
- 1,037 ac-ft
- Max storage
- 1,320 ac-ft
- Drainage area
- 18 sq mi
- Hazard class
- High
- Owner
- USDA FS
Source: USACE National Inventory of Dams, NID ID CO00494 · Operator website
Graded lakes near Lake Isabel
Lake Isabel has no grade, but these lakes within a short drive do.
Nearby Lakes in Custer County
Frequently asked questions about Lake Isabel
Where is Lake Isabel?
- Lake Isabel is a lake in Custer County, Colorado. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Lake Isabel?
- Lake Isabel in Custer County, Colorado is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 5.9 ft visibility. Phosphorus: 232 µg/L. Chlorophyll-a (algae): 0.8 µg/L. Surface area: 35 acres.
Is Lake Isabel safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
How deep is Lake Isabel?
- No published bathymetric survey covers Lake Isabel, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 12 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 35 acres.
Are there campgrounds on Lake Isabel?
- Lake Isabel has 5 public campgrounds from USGS The National Map within 5 km, including Southside, La Vista, St. Charles, Ponderosa. 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 Isabel across LakeQuality
Planning a trip around Great Sand Dunes?
Lake Isabel is about 32 miles from Great Sand Dunes National Park & Preserve. 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 Great Sand Dunes →More Colorado Lake Rankings
Other Lakes in Colorado
Eutrophic Lakes in Colorado
Where this data comes from
6 measurements from 2 monitoring stations, 2022. 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 · 2022
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)
Public campgrounds from USGS The National Map Structures, within about 3 miles