Jumbo Annex Lake
Logan County, Colorado100 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.
- Limited data
Jumbo Annex Lake in Logan County, Colorado is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 100 acres.
- Area
- 100 acres
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Watch Jumbo Annex Lake’s letter
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Why Jumbo Annex Lake 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 Jumbo Annex Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
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.
Jumbo Annex Lake is a 100-acre lake in Logan County, Colorado.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2023-11-06. Grade methodology: LakeQuality methodology.
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Jumbo Annex Lake
These readings exist but are not enough for an A–F grade — see why.
No clarity data.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples |
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 100 acres |
No bathymetric survey has been published for Jumbo Annex Lake, so its depth is not documented here.
Fishing Jumbo Annex Lake
Reservoir Info (USACE NID)
Jumbo Annex Lake is a man-made reservoir impounded by the Jumbo (completed 1977), built primarily for fish and wildlife pond on the South Platte River-Tr; earth-type dam, 38 ft tall and 1,900 ft long.
- Surface area
- 100 ac
- Normal storage
- 950 ac-ft
- Max storage
- 1,450 ac-ft
- Drainage area
- 1 sq mi
- Hazard class
- Low
- Owner
- COLORADO PARKS AND WILDLIFE
Source: USACE National Inventory of Dams, NID ID CO00382 · Operator website · Matched by proximity (0.08 km)
Graded lakes near Jumbo Annex Lake
Jumbo Annex Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Logan County
Frequently asked questions about Jumbo Annex Lake
Where is Jumbo Annex Lake?
- Jumbo Annex Lake is a lake in Logan 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 Jumbo Annex Lake?
- Jumbo Annex Lake in Logan County, Colorado is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 100 acres.
Is Jumbo Annex Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
Explore Jumbo Annex Lake across LakeQuality
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Where this data comes from
8 measurements from 1 monitoring station, 2022–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Colorado Dept. of Public Health & Environment-WQCD
21COL001_WQX8 samples · 2022–2023
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 (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.