Smith Lake
Kossuth County, Iowa53 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #1 of 1 in the county
- 35 ft max depth
- Public access
Smith Lake in Kossuth County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 2.4 ft visibility. Phosphorus: 154.5 µg/L. Chlorophyll-a (algae): 39.1 µg/L. Surface area: 53 acres.
- Clarity
- 2.4 ft
- Typical in September
- 69°F
- Max depth
- ~35 ft est.
- Area
- 53 acres
- Type
- Hypereutrophic
- Trend
- → Stable
- Public access
- Yes
Stays via Stay22
Stays near Smith Lake
Compare lakeside cabins, hotels, and vacation rentals near Smith Lake in Kossuth 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 Smith Lake are listed below.
Top-rated places to stay near Smith Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Iowa’s top lakes →
Watch Smith Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Free interactive depth-contour map of Smith Lake, reaching a maximum surveyed depth of 11 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Smith Lake is a 53-acre highly nutrient-loaded hypereutrophic lake in Kossuth County, Iowa with an estimated average depth of about 35 feet. Water quality is graded F based on 2 sampling years through 2024. Water clarity is declining over recent sampling years. Limited fish-species data available. Public access is available.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-19. 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. Smith Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for algal growth. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 2.4 ft of visibility. Phosphorus 154.5 µg/L. Chlorophyll-a 39.1 µg/L. TSI 69. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.4 ft | Not graded |
| Phosphorus | 154.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 39.1 µg/L | Poor |
| Trophic State Index (TSI) | 69 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Smith Lake typically sits around 69°F at the surface in September. Summer average is about 75°F. Usually warmest in Jul (about 81°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 26 field readings (2010–2023) via the EPA Water Quality Portal. See the full Smith Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~35 ft est. |
| Average Depth | ~7 ft est. |
| Surface Area | 53 acres |
| 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 Smith 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.
Fishing Smith Lake
Water Quality Trend: → Stable
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.08 m/yr | 4 |
| Phosphorus | ↑ Improving | -57.8 µg/L/yr | 4 |
| Chlorophyll-a | → Stable | +0.09 µg/L/yr | 4 |
Reservoir Info (USACE NID)
Smith Lake is a man-made reservoir impounded by the Lake Smith Dam (completed 1965), built primarily for recreation on the TR-BLACK CAT CREEK; earth-type dam, 21 ft tall and 570 ft long.
- Surface area
- 53 ac
- Normal storage
- 245 ac-ft
- Max storage
- 463 ac-ft
- Drainage area
- 1.8 sq mi
- Hazard class
- Significant
- Owner
- Kossuth County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA00570 · Operator website
EPA Impairment Status
Smith Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 04-EDM-981 · Official waterbody report
Regulated Pollution Sources Nearby
5 EPA-permitted facilities operate within about 5 miles of Smith Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 4 facilities have a reported Clean Water Act violation in the past three years.
- Algona City Of StpAlgona · 4.1 mi away · NPDES IA0022055MajorRecent violation
- Oak Lake Maintenance, Inc.Algona · 3 mi away · NPDES IA0065242Recent violation
- Smithfield Hog Production DivisionAlgona · 4.2 mi away · NPDES IA0073784Recent violation
- Burt City Of StpBurt · 4.9 mi away · NPDES IA0027405Recent violation
- Ag Processing, Inc. - AlgonaAlgona · 3.4 mi away · NPDES IA0081116
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 Kossuth County
Nearby Lakes in Kossuth County
Frequently asked questions about Smith Lake
Where is Smith Lake?
- Smith Lake is a lake in Kossuth County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Smith Lake?
- Smith Lake in Kossuth County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 2.4 ft visibility. Phosphorus: 154.5 µg/L. Chlorophyll-a (algae): 39.1 µg/L. Surface area: 53 acres.
Is Smith Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Smith Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for algal growth. Check local advisories before you swim.
What is the water temperature of Smith Lake?
- Smith Lake typically sits around 69°F at the surface in September, from 26 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Smith Lake?
- No published bathymetric survey covers Smith Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 35 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 53 acres.
Explore Smith Lake across LakeQuality
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
49 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_WQX49 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)