Browns Lake
Woodbury County, IowaView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Turbidity
- #3 of 3 in the county
- 28 ft max depth
- Public access
Browns Lake in Woodbury County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 0.7 ft visibility. Phosphorus: 217 µg/L. Chlorophyll-a (algae): 61.6 µg/L.
- Clarity
- 0.7 ft
- Typical in September
- 69°F
- Max depth
- ~28 ft est.
- Type
- Hypereutrophic
- Phosphorus
- 217 µg/L
- Chlorophyll-a
- 61.6 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Stays near Browns Lake
Compare lakeside cabins, hotels, and vacation rentals near Browns Lake in Woodbury 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 Browns Lake are listed below.
Top-rated places to stay near Browns Lake
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Free interactive depth-contour map of Browns Lake, reaching a maximum surveyed depth of 10 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Browns Lake is a highly nutrient-loaded hypereutrophic lake in Woodbury County, Iowa with an estimated average depth of about 28 feet. Water quality is graded F based on 1 sampling years through 2024. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 2 other monitored lakes in Woodbury County, Browns Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-03. Grade methodology: LakeQuality methodology.
What Browns Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
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, Browns Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 8 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: F (Algae-prone)
Very murky, less than 0.7 ft of visibility. Phosphorus 217 µg/L. Chlorophyll-a 61.6 µg/L. TSI 79. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 0.7 ft | Not graded |
| Phosphorus | 217 µg/L | Not graded |
| Chlorophyll-a (Algae) | 61.6 µg/L | Poor |
| Trophic State Index (TSI) | 79 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Browns Lake 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 May (about 64°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 31 field readings (2010–2023) via the EPA Water Quality Portal. See the full Browns Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~28 ft est. |
| Average Depth | ~8 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Iowa has not published bathymetry for Browns Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Brown's Lake Wildlife AreaPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Browns Lake
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.034 m/yr | 4 |
| Phosphorus | ↑ Improving | -60.6 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -14.17 µg/L/yr | 4 |
EPA Impairment Status
Browns Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IA 06-WEM-1735 · Official waterbody report
Regulated Pollution Sources Nearby
5 EPA-permitted facilities operate within about 5 miles of Browns Lake under Clean Water Act (NPDES) discharge permits, including 3 classified by the EPA as major dischargers. 3 facilities have a reported Clean Water Act violation in the past three years.
- Midamerican Energy - Neal North Energy CenterSergeant Bluff · 2.7 mi away · NPDES IA0004103MajorRecent violation
- Gelita Usa, Inc.Sergeant Bluff · 3.2 mi away · NPDES IA0004413MajorRecent violation
- Cf Industries Nitrogen, Llc - Port Neal Nitrogen ComplexSergeant Bluff · 3.2 mi away · NPDES IA0004014Major
- Ag Processing Inc. - Sergeant BluffSergeant Bluff · 1.7 mi away · NPDES IA0058815Recent violation
- Salix City Of StpSalix · 2.2 mi away · NPDES IA0032913
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 #3 of 3 lakes in Woodbury County
Nearby Lakes With Higher Grades
Browns Lake 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 Woodbury County
Frequently asked questions about Browns Lake
Where is Browns Lake?
- Browns Lake is a lake in Woodbury County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Browns Lake?
- Browns Lake in Woodbury County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 0.7 ft visibility. Phosphorus: 217 µg/L. Chlorophyll-a (algae): 61.6 µg/L.
Is Browns Lake safe to swim in?
- Based on E. coli testing, Browns Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 8 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. Browns Lake 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 Browns Lake?
- Browns Lake typically sits around 69°F at the surface in September, from 31 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Browns Lake?
- No published bathymetric survey covers Browns Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 28 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Browns Lake?
- Browns Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Brown's Lake Wildlife Area. Public access is listed as yes.
Explore Browns Lake across LakeQuality
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Where this data comes from
46 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_WQX46 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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory