South Prairie Lake
Black Hawk County, IowaView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- #6 of 7 in the county
South Prairie Lake in Black Hawk County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 104.5 µg/L. Chlorophyll-a (algae): 66.9 µg/L.
- Clarity
- 1.6 ft
- Typical in September
- 71°F
- Type
- Hypereutrophic
- Trend
- ↓ Declining
Stays via Stay22
Stays near South Prairie Lake
Compare lakeside cabins, hotels, and vacation rentals near South Prairie Lake in Black Hawk County, Iowa — 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 South Prairie Lake are listed below.
Top-rated places to stay near South Prairie Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
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Watch South Prairie Lake’s letter
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Free interactive depth-contour map of South Prairie Lake, reaching a maximum surveyed depth of 18 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
South Prairie Lake is a highly nutrient-loaded hypereutrophic lake in Black Hawk County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Compared to the 6 other monitored lakes in Black Hawk County, South Prairie Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-23. 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. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.6 ft of visibility. Phosphorus 104.5 µg/L. Chlorophyll-a 66.9 µg/L. TSI 71. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 104.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 66.9 µg/L | Poor |
| Trophic State Index (TSI) | 71 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
South Prairie Lake typically sits around 71°F at the surface in September. Summer average is about 77°F. Usually warmest in Jul (about 81°F) and coldest in Sep (about 71°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 29 field readings (2010–2023) via the EPA Water Quality Portal. See the full South Prairie Lake water temperature breakdown →
Fishing South Prairie Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.008 m/yr | 5 |
| Phosphorus | ↓ Declining | +11.6 µg/L/yr | 4 |
| Chlorophyll-a | ↓ Declining | +3.61 µg/L/yr | 5 |
Reservoir Info (USACE NID)
South Prairie Lake is a man-made reservoir impounded by the Viking Road Detention Dam (completed 1994), built primarily for flood risk reduction on the DRY CREEK; earth-type dam, 22 ft tall and 1,000 ft long.
- Normal storage
- 0 ac-ft
- Max storage
- 1,000 ac-ft
- Drainage area
- 6 sq mi
- Hazard class
- High
- Owner
- City of Cedar Falls
All listed purposes: Flood Risk Reduction;Other.
Source: USACE National Inventory of Dams, NID ID IA03104 · Operator website · Matched by proximity (0.7 km)
Regulated Pollution Sources Nearby
8 EPA-permitted facilities operate within about 5 miles of South Prairie Lake under Clean Water Act (NPDES) discharge permits. 6 facilities have a reported Clean Water Act violation in the past three years.
- Quad State Gauging & MeasurementCedar Falls · 0.4 mi away · NPDES IA0074071Recent violation
- Viking Pump, Inc. - Viking Road FacilityCedar Falls · 0.6 mi away · NPDES IA0078140Recent violation
- University Of Northern IowaCedar Falls · 2.4 mi away · NPDES IA0063941Recent violation
- Cedar Falls Mobile Home VillageCedar Falls · 2.9 mi away · NPDES IA0064033Recent violation
- Hudson City Of StpHudson · 4 mi away · NPDES IA0027243Recent violation
- Cedar Glen Mhc LlcCedar Falls · 4.5 mi away · NPDES IA0061689Recent violation
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 #6 of 7 lakes in Black Hawk County
Nearby Lakes With Higher Grades
South Prairie Lake holds Grade F. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Black Hawk County
Frequently asked questions about South Prairie Lake
Where is South Prairie Lake?
- South Prairie Lake is a lake in Black Hawk County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for South Prairie Lake?
- South Prairie Lake in Black Hawk County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 104.5 µg/L. Chlorophyll-a (algae): 66.9 µg/L.
Is South Prairie Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of South Prairie Lake?
- South Prairie Lake typically sits around 71°F at the surface in September, from 29 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore South Prairie Lake across LakeQuality
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
75 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Iowa DNR Surface Water Monitoring Data
21IOWA_WQX75 samples · 2020–2024
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)