Willow Creek Reservoir
Sarpy County, NebraskaView mapDirections
Nutrients and algae run well above the regional average.
↓ down from D at the last regrade
- Hypereutrophic
- Impaired · Mercury
- #5 of 6 in the county
Willow Creek Reservoir in Sarpy County, Nebraska has a water quality grade of F (Algae-prone). Water clarity: 1.5 ft visibility. Phosphorus: 96.7 µg/L. Chlorophyll-a (algae): 65.6 µg/L.
- Clarity
- 1.5 ft
- Type
- Hypereutrophic
- Phosphorus
- 96.7 µg/L
- Chlorophyll-a
- 65.6 µg/L
- Trend
- ↑ Improving
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Stays near Willow Creek Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Willow Creek Reservoir in Sarpy County, Nebraska — 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 Willow Creek Reservoir are listed below.
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Willow Creek Reservoir is a highly nutrient-loaded hypereutrophic lake in Sarpy County, Nebraska. Water quality is graded F based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Compared to the 5 other monitored lakes in Sarpy County, Willow Creek Reservoir ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, NDEE, last sampled 2024-09-05. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyAlgae risk
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 F is nutrients and algae, not a swimming clearance. Willow Creek Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.5 ft of visibility. Phosphorus 96.7 µg/L. Chlorophyll-a 65.6 µg/L. TSI 71. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.5 ft | Not graded |
| Phosphorus | 96.7 µg/L | Poor |
| Chlorophyll-a (Algae) | 65.6 µg/L | Poor |
| Trophic State Index (TSI) | 71 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Fishing Willow Creek Reservoir
Water Quality Trend: ↑ Improving
Based on 13 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.503 m/yr | 13 |
| Phosphorus | ↓ Declining | +3.04 µg/L/yr | 5 |
| Chlorophyll-a | ↑ Improving | -6.56 µg/L/yr | 12 |
EPA Impairment Status
Willow Creek Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit NE-MT1-L0027 · Official waterbody report · Matched by proximity (0.05 km)
County Ranking
Ranked #5 of 6 lakes in Sarpy County
Nearby Lakes With Higher Grades
Willow Creek Reservoir holds Grade F. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Sarpy County
Frequently asked questions about Willow Creek Reservoir
Where is Willow Creek Reservoir?
- Willow Creek Reservoir is a lake in Sarpy County, Nebraska. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Willow Creek Reservoir?
- Willow Creek Reservoir in Sarpy County, Nebraska has a water quality grade of F (Algae-prone). Water clarity: 1.5 ft visibility. Phosphorus: 96.7 µg/L. Chlorophyll-a (algae): 65.6 µg/L.
Is Willow Creek Reservoir safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Willow Creek Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Explore Willow Creek Reservoir across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Nebraska's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
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Where this data comes from
157 measurements from 1 monitoring station, 2012–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Nebraska Department of Environment and Energy
21NEB001_WQX157 samples · 2012–2024
Analytical methods
- Total Phosphorus After Block Digestion
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 447.0 ~ EPA; Chlorophyll a and b in phytoplankton by HPLC/UV
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.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database