South Prairie Lake
Black Hawk County, IowaView mapDirections
Iowa DNR publishes the water-quality measurements for South Prairie Lake. Here is what has been measured.
- Hypereutrophic
South Prairie Lake in Black Hawk County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 1.6 ft visibility. Phosphorus: 104.5 µg/L. Chlorophyll-a (algae): 66.9 µg/L.
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. 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. 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. Check local advisories before you swim.
Whether South Prairie Lake is safe to swim in today is a call for the Iowa Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for South Prairie Lake
These are the measurements Iowa DNR publishes for South Prairie Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 1.6 ft of visibility. Phosphorus 104.5 µg/L. Chlorophyll-a 66.9 µg/L. TSI 71.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 105µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 66.9µg/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. | 71 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about South Prairie Lake
Answers come straight from the public measurements and survey records on this page.
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.
Column height runs from this lake’s coldest month (71°F) to its warmest (81°F).
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 →
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 readings cover 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 Oct 23–25, 4 adults. Change dates on the map below.
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Fishing South Prairie Lake
Water Quality Trend: Worsening
Based on 5 years of monitoring (2020–2024).
Water clarity
Stable5 years
Phosphorus
Worsening+11.6 µg/L/yr4 years
Chlorophyll-a
Worsening+3.61 µg/L/yr5 years
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.
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. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of South Prairie Lake?
- South Prairie Lake in Black Hawk County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. 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?
- Nutrient and algae readings are 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
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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)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)