Lost Island Lake
Palo Alto County, IowaView mapDirections
Iowa DNR publishes the water-quality measurements for Lost Island Lake. Here is what has been measured.
- Eutrophic
- 48 ft max depth
- Public access
Lost Island Lake in Palo Alto County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.6 ft visibility. Phosphorus: 68 µg/L. Chlorophyll-a (algae): 19.1 µg/L.
Free interactive depth-contour map of Lost Island Lake, reaching a maximum surveyed depth of 12 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Lost Island Lake is a productive, nutrient-rich eutrophic lake in Palo Alto County, Iowa with an estimated average depth of about 48 feet. Overall water quality is declining 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 Palo Alto County, Lost Island Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-11. Methodology: how these readings are compared.
Lost Island Lake has one public boat landing. For a place on the water, look through cabin and lake-house rentals near Lost Island Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Lost Island Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
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. Check local advisories before you swim.
Whether Lost Island 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 Lost Island Lake
These are the measurements Iowa DNR publishes for Lost Island 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 2.6 ft of visibility. Phosphorus 68 µg/L. Chlorophyll-a 19.1 µg/L. TSI 63.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 68µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 19.1µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 63 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lost Island Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lost Island Lake typically sits around 71°F at the surface in September. Summer average is about 74°F. Usually warmest in Jul (about 80°F) and coldest in May (about 70°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (70°F) to its warmest (80°F).
Typical surface water temperature by month, from 34 field readings (2010–2023) via the EPA Water Quality Portal. See the full Lost Island Lake water temperature breakdown →
Lake Details
Max depth
~48 ft est.
Public access
Yes
Listed by Iowa DNR
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Iowa has not published bathymetry for Lost Island Lake.
Lake Size & Watershed
Watershed (drainage) area
11 sq mi
HydroLAKES / HydroSHEDS
Surface area
1,119 acres
HydroLAKES / HydroSHEDS
Shoreline
6.2 mi
HydroLAKES / HydroSHEDS
Elevation
1,335 ft
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
- Dewey's Pasture ComplexPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Lost Island Lake
Compare lakeside cabins, hotels, and vacation rentals near Lost Island Lake in Palo Alto 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 Lost Island Lake are listed below.
Top-rated places to stay near Lost Island Lake
Prices for Oct 23–25, 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 trip? Cabins and lodging at Lost Island Lake → · more Iowa lake trips
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Fishing Lost Island Lake
Water Quality Trend: Worsening
Based on 5 years of monitoring (2020–2024).
Water clarity
Worsening5 years
Phosphorus
Worsening+14.05 µg/L/yr4 years
Chlorophyll-a
Worsening+3.73 µg/L/yr5 years
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Lost Island Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Ruthven City Of StpRuthven · 3.4 mi away · NPDES IA0032441Recent 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 Palo Alto County
Frequently asked questions about Lost Island Lake
Where is Lost Island Lake?
- Lost Island Lake is a lake in Palo Alto County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Lost Island Lake?
- Lost Island Lake in Palo Alto County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.6 ft visibility. Phosphorus: 68 µg/L. Chlorophyll-a (algae): 19.1 µg/L.
Is Lost Island Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Lost Island Lake?
- Lost Island Lake typically sits around 71°F at the surface in September, from 34 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Lost Island Lake?
- No published bathymetric survey covers Lost Island Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 48 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 Lost Island Lake?
- Lost Island Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Dewey's Pasture Complex. Public access is listed as yes.
Can I fish at Lost Island Lake?
- Lost Island Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Iowa's fish and wildlife agency, so check its current regulations before you go.
Explore Lost Island Lake across LakeQuality
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Where this data comes from
57 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_WQX57 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
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