Horse Creek Outlet Lake
Weld County, Colorado712 acresView mapDirections
Colorado WQCD publishes the water-quality measurements for Horse Creek Outlet Lake. Here is what has been measured.
- Eutrophic
- Impaired · pH / acidity
- 56 ft max depth
Horse Creek Outlet Lake in Weld County, Colorado has water-quality measurements published by Colorado WQCD, shown here as reported. Phosphorus: 460 µg/L. Chlorophyll-a (algae): 27.6 µg/L. Surface area: 712 acres.
Horse Creek Outlet Lake is a 712-acre productive, nutrient-rich eutrophic lake in Weld County, Colorado with an estimated average depth of about 56 feet. Overall water quality is declining over recent sampling years. Compared to the 4 other monitored lakes in Weld County, Horse Creek Outlet Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, CDPHE, last sampled 2024-08-28. Methodology: how these readings are compared.
Swimming conditions
Readings onlyAlgae risk
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Horse Creek Outlet Lake is listed impaired under Clean Water Act §303(d) (IR 5) for pH / acidity. Check local advisories before you swim.
Whether Horse Creek Outlet Lake is safe to swim in today is a call for the Water Quality Control Division of the Colorado Department of Public Health and Environment and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Horse Creek Outlet Lake
These are the measurements Colorado WQCD publishes for Horse Creek Outlet Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 460 µg/L. Chlorophyll-a 27.6 µg/L. TSI 78.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 460µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 27.6µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 78 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Horse Creek Outlet Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~56 ft est.
Surface area
712 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 Horse Creek Outlet Lake.
Lake Size & Watershed
Watershed (drainage) area
27 sq mi
HydroLAKES / HydroSHEDS
Shoreline
6.5 mi
HydroLAKES / HydroSHEDS
Elevation
5,082 ft
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.
Stays via Stay22
Stays near Horse Creek Outlet Lake
Compare lakeside cabins, hotels, and vacation rentals near Horse Creek Outlet Lake in Weld 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Horse Creek Outlet Lake are listed below.
Top-rated places to stay near Horse Creek Outlet Lake
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Fishing Horse Creek Outlet Lake
Water Quality Trend: Worsening
Based on 4 years of monitoring (2020–2024).
Phosphorus
Stable-7.29 µg/L/yr4 years
Chlorophyll-a
Worsening+8.85 µg/L/yr4 years
Reservoir Info (USACE NID)
Horse Creek Outlet Lake is a man-made reservoir impounded by the Horse Creek (completed 1910), built primarily for irrigation on the Horse Creek; earth-type dam, 39 ft tall and 4,800 ft long.
- Surface area
- 712 ac
- Normal storage
- 15,537 ac-ft
- Max storage
- 29,739 ac-ft
- Drainage area
- 26 sq mi
- Hazard class
- High
- Owner
- HENRYLYN IRRIGATION DISTRICT
Source: USACE National Inventory of Dams, NID ID CO00012 · Operator website · Matched by proximity (0.52 km)
EPA Impairment Status
Horse Creek Outlet Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit COSPMS07_C · Official waterbody report
Nearby Lakes in Weld County
Frequently asked questions about Horse Creek Outlet Lake
Where is Horse Creek Outlet Lake?
- Horse Creek Outlet Lake is a lake in Weld County, Colorado. Its water-quality measurements are published by Colorado WQCD and shown on this page as reported.
What is the water quality of Horse Creek Outlet Lake?
- Horse Creek Outlet Lake in Weld County, Colorado has water-quality measurements published by Colorado WQCD, shown here as reported. Phosphorus: 460 µg/L. Chlorophyll-a (algae): 27.6 µg/L. Surface area: 712 acres.
Is Horse Creek Outlet Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Horse Creek Outlet Lake is listed impaired under Clean Water Act §303(d) (IR 5) for pH / acidity. Check local advisories before you swim.
How deep is Horse Creek Outlet Lake?
- No published bathymetric survey covers Horse Creek Outlet Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 56 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 712 acres.
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Where this data comes from
78 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Metro Water Recovery (formerly Metro Wastewater Reclamation District)
MWRD_WQX78 samples · 2020–2024
Analytical methods
- 4500 P H ~ Manual Digestion and Flow Injection Analysis for Total Phosphorus
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)