Lost Island Lake
Palo Alto County, IowaView mapDirections
Nutrients and algae run above the regional average.
- Eutrophic
- #1 of 3 in the county
- 48 ft max depth
- Public access
Lost Island Lake in Palo Alto County, Iowa has a water quality grade of D (Nutrient-rich). Water clarity: 2.6 ft visibility. Phosphorus: 68 µg/L. Chlorophyll-a (algae): 19.1 µg/L.
- Clarity
- 2.6 ft
- Typical in September
- 71°F
- Max depth
- ~48 ft est.
- Type
- Eutrophic
- Phosphorus
- 68 µg/L
- Chlorophyll-a
- 19.1 µg/L
- Trend
- ↓ Declining
- Public access
- Yes
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 grade measures 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 Sep 11–13, 4 adults. Change dates on the map below.
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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. 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 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. Grade methodology: LakeQuality methodology.
What Lost Island Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
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 D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 2.6 ft of visibility. Phosphorus 68 µg/L. Chlorophyll-a 19.1 µg/L. TSI 63. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | Not graded |
| Phosphorus | 68 µg/L | Poor |
| Chlorophyll-a (Algae) | 19.1 µg/L | Fair |
| Trophic State Index (TSI) | 63 | Eutrophic |
High nutrients, frequent algae, reduced clarity
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.
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
| Characteristic | Value |
|---|---|
| Maximum Depth | ~48 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 Lost Island 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
- Dewey's Pasture ComplexPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
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 |
| Phosphorus | ↓ Declining | +14.05 µg/L/yr | 4 |
| Chlorophyll-a | ↓ Declining | +3.73 µg/L/yr | 5 |
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.
County Ranking
Ranked #1 of 3 lakes in Palo Alto County
Nearby Lakes With Higher Grades
Lost Island Lake holds Grade D. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →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. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lost Island Lake?
- Lost Island Lake in Palo Alto County, Iowa has a water quality grade of D (Nutrient-rich). 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?
- The D is nutrients and algae, 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.
Explore Lost Island Lake across LakeQuality
More Iowa Lake Rankings
Other Grade D Lakes in Iowa
Eutrophic Lakes in Iowa
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)
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
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