Lake Iowa
Iowa County, Iowa92 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Lake Iowa. Here is what has been measured.
- Hypereutrophic
- Impaired · Algal growth
Lake Iowa in Iowa County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 1.9 ft visibility. Phosphorus: 80 µg/L. Chlorophyll-a (algae): 53.8 µg/L. Surface area: 92 acres.
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. Overall water quality is improving over recent sampling years.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-01. Methodology: how these readings are compared.
Swimming conditions
Readings onlyBacteria advisory
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.
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.
Whether Lake Iowa 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 Lake Iowa
These are the measurements Iowa DNR publishes for Lake Iowa, 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 1.9 ft of visibility. Phosphorus 80 µg/L. Chlorophyll-a 53.8 µg/L. TSI 68.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 80µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 53.8µg/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. | 68 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Lake Iowa
Answers come straight from the public measurements and survey records on this page.
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.
Column height runs from this lake’s coldest month (69°F) to its warmest (80°F).
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
Surface area
92 acres
No bathymetric survey has been published for Lake Iowa, so its depth is not documented here.
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 readings cover nutrients and algae, not lodging. Cabins and rentals around Lake Iowa are listed below.
Top-rated places to stay near Lake Iowa
Prices for Oct 23–25, 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 →
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Fishing Lake Iowa
Water Quality Trend: Improving
Based on 5 years of monitoring (2020–2024).
Water clarity
Improving5 years
Phosphorus
Improving-3.2 µg/L/yr4 years
Chlorophyll-a
Worsening+3.42 µg/L/yr5 years
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
Designated uses not supporting: Recreation.
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.
Nearby Lakes in Iowa County
Frequently asked questions about Lake Iowa
Where is Lake Iowa?
- Lake Iowa is a lake in Iowa County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Lake Iowa?
- Lake Iowa in Iowa County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. 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 is a historical summary of past bacteria testing, not a current reading and not a swimming clearance. Bacteria levels can spike quickly after heavy rain, so whether Lake Iowa is safe to swim in today is a call for Iowa's water agency and the county health department; check their current beach 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
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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)
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)