Lost Island Lake is a productive, nutrient-rich eutrophic lake in Palo Alto County, Iowa. Water quality is graded D based on 2 sampling years through 2024. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 6 public boat landings. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 2.6 ft of visibility. Chlorophyll-a: 19.1 µg/L. Trophic State Index: 61.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 19.1 µg/L | C |
| Trophic State Index (TSI) | 61 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay 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.
Top-rated places to stay near Lost Island Lake
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Fishing Lost Island Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.285 m/yr | 5 |
| Chlorophyll-a | ↓ Declining | +3.73 µg/L/yr | 5 |
Recreation & Access
Water Temperature
Lost Island Lake averages about 74°F at the surface in summer, usually warmest in Jul (about 80°F) and coldest in May (about 70°F). These are typical values by month — not a live reading.
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 →
Location & Depth Map
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.
County Ranking
Ranked #1 of 3 lakes in Palo Alto County
Cleaner Lakes Within 30 Miles
Lost Island Lake holds Grade D. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Palo Alto County
Explore Lost Island Lake across LakeGrade
More Iowa Lake Rankings
Other Grade D Lakes in Iowa
Eutrophic Lakes in Iowa
More records, surveys & data sources
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-09-11
Monitoring stations: 1