Little Sioux Park Lake
Woodbury County, IowaView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
↑ up from C at the last regrade
- Mesotrophic
- #1 of 3 in the county
Little Sioux Park Lake in Woodbury County, Iowa has a water quality grade of A (Excellent). Water clarity: 5.7 ft visibility. Phosphorus: 19 µg/L. Chlorophyll-a (algae): 5.7 µg/L.
- Clarity
- 5.7 ft
- Typical in August
- 79°F
- Type
- Mesotrophic
- Trend
- ↓ Declining
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Watch Little Sioux Park Lake’s letter
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Free interactive depth-contour map of Little Sioux Park Lake, reaching a maximum surveyed depth of 28 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Little Sioux Park Lake is a mesotrophic lake in Woodbury County, Iowa. Water quality is graded A based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Compared to the 2 other monitored lakes in Woodbury County, Little Sioux Park Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-03. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyBacteria A
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.
Based on E. coli testing, Little Sioux Park Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 5 samples across 2 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Iowa’s current beach and health-department advisories before swimming.
Water Quality Grade: A (Excellent)
Murky, only visible to about 5.7 ft. Phosphorus 19 µg/L. Chlorophyll-a 5.7 µg/L. TSI 49. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.7 ft | Not graded |
| Phosphorus | 19 µg/L | Good |
| Chlorophyll-a (Algae) | 5.7 µg/L | Good |
| Trophic State Index (TSI) | 49 | Mesotrophic |
Moderate nutrients, good water quality
Water Temperature
Little Sioux Park Lake typically sits around 79°F at the surface in August. Summer average is about 79°F. Usually warmest in Jun (about 79°F) and coldest in May (about 65°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 26 field readings (2010–2023) via the EPA Water Quality Portal. See the full Little Sioux Park Lake water temperature breakdown →
Fishing Little Sioux Park Lake
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.468 m/yr | 4 |
| Phosphorus | → Stable | +0.15 µg/L/yr | 4 |
| Chlorophyll-a | ↓ Declining | +0.25 µg/L/yr | 4 |
Regulated Pollution Sources Nearby
4 EPA-permitted facilities operate within about 5 miles of Little Sioux Park Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Correctionville City Of StpCorrectionville · 1.9 mi away · NPDES IA0023531Recent violation
- Iowa Dot Maintenance Garage-CorrectionvilleCorrectionville · 2.8 mi away · NPDES IA0076325
- Pithan Feedlots, Inc.Anthon · 4.4 mi away · NPDES IA0080683
- Anthon City Of StpAnthon · 4.5 mi away · NPDES IA0042854
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #1 of 3 lakes in Woodbury County
Nearby Lakes in Woodbury County
Frequently asked questions about Little Sioux Park Lake
Where is Little Sioux Park Lake?
- Little Sioux Park Lake is a lake in Woodbury County, Iowa. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Little Sioux Park Lake?
- Little Sioux Park Lake in Woodbury County, Iowa has a water quality grade of A (Excellent). Water clarity: 5.7 ft visibility. Phosphorus: 19 µg/L. Chlorophyll-a (algae): 5.7 µg/L.
Is Little Sioux Park Lake safe to swim in?
- Based on E. coli testing, Little Sioux Park Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 5 samples across 2 seasons. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Little Sioux Park Lake has a water quality grade of A (Excellent). Bacteria levels can spike quickly after heavy rain, so always check Iowa's current beach and health-department advisories before you swim.
What is the water temperature of Little Sioux Park Lake?
- Little Sioux Park Lake typically sits around 79°F at the surface in August, from 26 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore Little Sioux Park Lake across LakeQuality
More Iowa Lake Rankings
Other Grade A Lakes in Iowa
Mesotrophic Lakes in Iowa
Where this data comes from
53 measurements from 1 monitoring station, 2021–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX53 samples · 2021–2024
Analytical methods
- Unknown
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- In-Vitro Determination of Chlorophyll
- ISU modification of APHA 2130-B
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)