Deweese Reservoir
Custer County, Colorado295 acresView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- #1 of 1 in the county
- 21 ft max depth
- Public access
Deweese Reservoir in Custer County, Colorado has a water quality grade of D (Nutrient-rich). Water clarity: 5.2 ft visibility. Phosphorus: 41.5 µg/L. Chlorophyll-a (algae): 13.5 µg/L. Surface area: 295 acres.
- Clarity
- 5.2 ft
- Max depth
- ~21 ft est.
- Area
- 295 acres
- Type
- Eutrophic
- Trend
- → Stable
- Public access
- Yes
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Stays near Deweese Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Deweese Reservoir in Custer 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 grade measures nutrients and algae, not lodging — cabins and rentals around Deweese Reservoir are listed below.
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Deweese Reservoir is a 295-acre productive, nutrient-rich eutrophic lake in Custer County, Colorado with an estimated average depth of about 21 feet. Water quality is graded D based on 3 sampling years through 2025. Phosphorus level is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2025-10-01. Grade methodology: LakeQuality methodology.
What Deweese Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Grade onlyElevated nutrients
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 D is nutrients and algae, not a swimming clearance. Deweese Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury), nutrients (phosphorus, nitrogen), oxygen depletion (low DO). Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 5.2 ft. Phosphorus 41.5 µg/L. Chlorophyll-a 13.5 µg/L. TSI 56. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.2 ft | Not graded |
| Phosphorus | 41.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 13.5 µg/L | Poor |
| Trophic State Index (TSI) | 56 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~21 ft est. |
| Average Depth | ~12 ft est. |
| Surface Area | 295 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 Deweese 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
- DeWeese Reservoir State Wildlife AreaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Deweese Reservoir
Water Quality Trend: → Stable
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.004 m/yr | 3 |
| Phosphorus | ↑ Improving | -15.25 µg/L/yr | 2 |
| Chlorophyll-a | ↓ Declining | +0.44 µg/L/yr | 3 |
Reservoir Info (USACE NID)
Deweese Reservoir is a man-made reservoir impounded by the Deweese (completed 1903), built primarily for irrigation on the Grape Creek; arch-type dam, 63 ft tall and 386 ft long.
- Surface area
- 295 ac
- Normal storage
- 4,338 ac-ft
- Max storage
- 4,441 ac-ft
- Drainage area
- 370 sq mi
- Hazard class
- High
- Owner
- DE WEESE DYE DITCH & RES. CO. (ARLIN BOLKEMA, PRES
All listed purposes: Irrigation;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID CO02068 · Operator website
EPA Impairment Status
Deweese 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 COARUA35_A · Official waterbody report
County Ranking
Ranked #1 of 1 lakes in Custer County
Nearby Lakes in Custer County
Frequently asked questions about Deweese Reservoir
Where is Deweese Reservoir?
- Deweese Reservoir is a lake in Custer County, Colorado. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Deweese Reservoir?
- Deweese Reservoir in Custer County, Colorado has a water quality grade of D (Nutrient-rich). Water clarity: 5.2 ft visibility. Phosphorus: 41.5 µg/L. Chlorophyll-a (algae): 13.5 µg/L. Surface area: 295 acres.
Is Deweese Reservoir safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Deweese Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury), nutrients (phosphorus, nitrogen), oxygen depletion (low DO). Check local advisories before you swim.
How deep is Deweese Reservoir?
- No published bathymetric survey covers Deweese Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 21 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 295 acres.
Are there boat ramps on Deweese Reservoir?
- Deweese Reservoir has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include DeWeese Reservoir State Wildlife Area. Public access is listed as yes.
Explore Deweese Reservoir across LakeQuality
2 thermal springs within 19.7 mi, nearest Canon City Hot Springs
Species activity outlook by water temperature and season
Where to stay at Colorado's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Colorado's cleanest and most-polluted lakes, ranked
Planning a trip around Great Sand Dunes?
Deweese Reservoir is about 29 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 Grade D Lakes in Colorado
Eutrophic Lakes in Colorado
Where this data comes from
78 measurements from 5 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Colorado Dept. of Public Health & Environment-WQCD
21COL001_WQX78 samples · 2020–2025
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)
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)
Named boat-access points from the USGS National Boat Ramps inventory