Lake Iowa
Iowa County, Iowa92 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #1 of 1 in the county
Lake Iowa in Iowa County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.9 ft visibility. Phosphorus: 80 µg/L. Chlorophyll-a (algae): 53.8 µg/L. Surface area: 92 acres.
- Clarity
- 1.9 ft
- Typical in September
- 69°F
- Area
- 92 acres
- Type
- Hypereutrophic
- Phosphorus
- 80 µg/L
- Chlorophyll-a
- 53.8 µg/L
- Trend
- ↑ Improving
Stays via Stay22
Stays near Lake Iowa
Compare lakeside cabins, hotels, and vacation rentals near Lake Iowa in Iowa 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 Lake Iowa are listed below.
Top-rated places to stay near Lake Iowa
Prices for Sep 11–13, 4 adults. Change dates on the map below.
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Planning a whole trip? See where to stay at Iowa’s top lakes →
Watch Lake Iowa’s letter
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Free interactive depth-contour map of Lake Iowa, reaching a maximum surveyed depth of 28 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Lake Iowa is a 92-acre highly nutrient-loaded hypereutrophic lake in Iowa County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-01. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyBacteria A · advisory
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, Lake Iowa never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 17 samples across 6 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: F (Algae-prone)
Very murky, less than 1.9 ft of visibility. Phosphorus 80 µg/L. Chlorophyll-a 53.8 µg/L. TSI 68. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.9 ft | Not graded |
| Phosphorus | 80 µg/L | Poor |
| Chlorophyll-a (Algae) | 53.8 µg/L | Poor |
| Trophic State Index (TSI) | 68 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Lake Iowa typically sits around 69°F at the surface in September. Summer average is about 78°F. Usually warmest in Jul (about 80°F) and coldest in Sep (about 69°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 38 field readings (2010–2023) via the EPA Water Quality Portal. See the full Lake Iowa water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 92 acres |
No bathymetric survey has been published for Lake Iowa, so its depth is not documented here.
Fishing Lake Iowa
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.097 m/yr | 5 |
| Phosphorus | ↑ Improving | -3.2 µg/L/yr | 4 |
| Chlorophyll-a | ↓ Declining | +3.42 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Lake Iowa is a man-made reservoir impounded by the Lake Iowa Dam (completed 1962), built primarily for recreation on the PIG CREEK; earth-type dam, 40 ft tall and 893 ft long.
- Surface area
- 92 ac
- Normal storage
- 1,110 ac-ft
- Max storage
- 1,950 ac-ft
- Drainage area
- 2.17 sq mi
- Hazard class
- Significant
- Owner
- Iowa County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA00520 · Operator website
EPA Impairment Status
Lake Iowa is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 02-IOW-677 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Lake Iowa under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- East Iowa Bible Camp-StpDeep River · 4.4 mi away · NPDES IA0075213Recent 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 #1 of 1 lakes in Iowa County
Nearby Lakes With Higher Grades
Lake Iowa 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 Iowa County
Frequently asked questions about Lake Iowa
Where is Lake Iowa?
- Lake Iowa is a lake in Iowa County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Iowa?
- Lake Iowa in Iowa County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.9 ft visibility. Phosphorus: 80 µg/L. Chlorophyll-a (algae): 53.8 µg/L. Surface area: 92 acres.
Is Lake Iowa safe to swim in?
- Based on E. coli testing, Lake Iowa never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 17 samples across 6 seasons. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Lake Iowa has a water quality grade of F (Algae-prone). 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 Lake Iowa?
- Lake Iowa typically sits around 69°F at the surface in September, from 38 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore Lake Iowa across LakeQuality
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
76 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_WQX76 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
- 2130 B ~ Nephelometric Method
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)