Manteno Lake
Shelby County, Iowa4 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Manteno Lake. Here is what has been measured.
- Eutrophic
- Impaired · Oxygen depletion (low DO)
Manteno Lake in Shelby County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.7 ft visibility. Phosphorus: 138.5 µg/L. Chlorophyll-a (algae): 28.3 µg/L. Surface area: 4.4 acres.
Free interactive depth-contour map of Manteno Lake, reaching a maximum surveyed depth of 8 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Manteno Lake is a 4-acre productive, nutrient-rich eutrophic lake in Shelby County, Iowa. Water clarity is improving over recent sampling years. Compared to the 5 other monitored lakes in Shelby County, Manteno Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-03. 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. Manteno Lake is listed impaired under Clean Water Act §303(d) (IR 5) for oxygen depletion (low DO). Check local advisories before you swim.
Whether Manteno 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 Manteno Lake
These are the measurements Iowa DNR publishes for Manteno 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 2.7 ft of visibility. Phosphorus 138.5 µg/L. Chlorophyll-a 28.3 µg/L. TSI 67.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 139µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 28.3µg/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. | 67 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Manteno Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Manteno Lake typically sits around 77°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 77°F) and coldest in May (about 64°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (64°F) to its warmest (77°F).
Typical surface water temperature by month, from 28 field readings (2010–2023) via the EPA Water Quality Portal. See the full Manteno Lake water temperature breakdown →
Lake Details
Surface area
4 acres
No bathymetric survey has been published for Manteno Lake, so its depth is not documented here.
Stays via Stay22
Stays near Manteno Lake
Compare lakeside cabins, hotels, and vacation rentals near Manteno Lake in Shelby 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 Manteno Lake are listed below.
Top-rated places to stay near Manteno Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
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Fishing Manteno Lake
Water Quality Trend: Stable
Based on 5 years of monitoring (2020–2024).
Water clarity
Improving5 years
Phosphorus
Worsening+23.35 µg/L/yr4 years
Chlorophyll-a
Stable-0.69 µg/L/yr5 years
Reservoir Info (USACE NID)
Manteno Lake is a man-made reservoir impounded by the Mill Picayune Watershed Site M-24-10 (completed 1964), built primarily for fire protection, stock, or small fish pond on the MILL CREEK; earth-type dam, 36 ft tall and 787 ft long.
- Surface area
- 4.4 ac
- Normal storage
- 30 ac-ft
- Max storage
- 166 ac-ft
- Drainage area
- 3.8 sq mi
- Hazard class
- Low
- Owner
- Shelby County SWCD
All listed purposes: Fire Protection, Stock, Or Small Fish Pond;Flood Risk Reduction.
Source: USACE National Inventory of Dams, NID ID IA00992 · Operator website · Matched by proximity (0.06 km)
EPA Impairment Status
Manteno Lake 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: Aquatic life.
Source: EPA ATTAINS assessment unit IA 06-BOY-1505 · Official waterbody report
Nearby Lakes in Shelby County
Frequently asked questions about Manteno Lake
Where is Manteno Lake?
- Manteno Lake is a lake in Shelby County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Manteno Lake?
- Manteno Lake in Shelby County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.7 ft visibility. Phosphorus: 138.5 µg/L. Chlorophyll-a (algae): 28.3 µg/L. Surface area: 4.4 acres.
Is Manteno Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Manteno Lake is listed impaired under Clean Water Act §303(d) (IR 5) for oxygen depletion (low DO). Check local advisories before you swim.
What is the water temperature of Manteno Lake?
- Manteno Lake typically sits around 77°F at the surface in August, from 28 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
Explore Manteno Lake across LakeQuality
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Where this data comes from
49 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_WQX49 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
Impairment status from EPA ATTAINS 303(d) database