Little River Lake
Decatur County, Iowa787 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Little River Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Mercury
- 44 ft max depth
- Public access
Little River Lake in Decatur County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.3 ft visibility. Phosphorus: 85 µg/L. Chlorophyll-a (algae): 70 µg/L. Surface area: 787 acres.
Free interactive depth-contour map of Little River Lake, reaching a maximum surveyed depth of 32 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Little River Lake is a 787-acre highly nutrient-loaded hypereutrophic lake in Decatur County, Iowa with an estimated average depth of about 44 feet. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 2 other monitored lakes in Decatur County, Little River Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-30. Methodology: how these readings are compared.
Little River Lake covers about 790 acres in Decatur County. It has 3 public boat landings, so a lakefront rental is not the only way to get a boat on the water. Vrbo is where to look for cabins and lake homes around Little River Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Little River Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch3 documented ramps
Swimming conditions
Readings onlyBacteria advisory
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.
Based on E. coli testing, Little River Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 16.7% of 6 samples across 2 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Iowa’s current beach and health-department advisories before swimming.
Whether Little River 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 Little River Lake
These are the measurements Iowa DNR publishes for Little River 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 2.3 ft of visibility. Phosphorus 85 µg/L. Chlorophyll-a 70 µg/L. TSI 69.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 85µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 70µg/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. | 69 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Little River Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Little River Lake typically sits around 76°F at the surface in September. Summer average is about 78°F. Usually warmest in Jul (about 79°F) and coldest in May (about 65°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (65°F) to its warmest (79°F).
Typical surface water temperature by month, from 31 field readings (2010–2023) via the EPA Water Quality Portal. See the full Little River Lake water temperature breakdown →
Lake Details
Max depth
~44 ft est.
Surface area
787 acres
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 Little River Lake.
Lake Size & Watershed
Watershed (drainage) area
22 sq mi
HydroLAKES / HydroSHEDS
Shoreline
11.5 mi
HydroLAKES / HydroSHEDS
Elevation
1,040 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
- Little RiverPublic
- Little RiverPublic
- Little River Recreatioal ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Little River Lake
Compare lakeside cabins, hotels, and vacation rentals near Little River Lake in Decatur 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 Little River Lake are listed below.
Top-rated places to stay near Little River Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
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Planning a trip? Cabins and lodging at Little River Lake → · more Iowa lake trips
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Fishing Little River Lake
Water Quality Trend: Improving
Based on 4 years of monitoring (2021–2024).
Water clarity
Improving4 years
Phosphorus
Improving-6.9 µg/L/yr4 years
Chlorophyll-a
Improving-6.34 µg/L/yr4 years
Reservoir Info (USACE NID)
Little River Lake is a man-made reservoir impounded by the Little River Watershed Site M-1 (completed 1984), built primarily for flood risk reduction on the LITTLE RIVER; earth-type dam, 61 ft tall and 1,810 ft long.
- Surface area
- 787 ac
- Normal storage
- 10,869 ac-ft
- Max storage
- 32,650 ac-ft
- Drainage area
- 20.85 sq mi
- Hazard class
- High
- Owner
- Decatur County SWCD
All listed purposes: Flood Risk Reduction;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IA02263 · Operator website · Matched by proximity (0.25 km)
EPA Impairment Status
Little River 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: Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 05-GRA-1358 · Official waterbody report
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Little River Lake under Clean Water Act (NPDES) discharge permits. 3 facilities have a reported Clean Water Act violation in the past three years.
- Leon Water Treatment PlantLeon · 0.5 mi away · NPDES IA0081787Recent violation
- Leon City Of StpLeon · 2.4 mi away · NPDES IA0027871Recent violation
- Decatur City-Stp-SirwaDecatur · 2.7 mi away · NPDES IA0072745Recent 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 Decatur County
Frequently asked questions about Little River Lake
Where is Little River Lake?
- Little River Lake is a lake in Decatur County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Little River Lake?
- Little River Lake in Decatur County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.3 ft visibility. Phosphorus: 85 µg/L. Chlorophyll-a (algae): 70 µg/L. Surface area: 787 acres.
Is Little River Lake safe to swim in?
- Based on E. coli testing, Little River Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 16.7% of 6 samples across 2 seasons. That is a historical summary of past bacteria testing, not a current reading and not a swimming clearance. Bacteria levels can spike quickly after heavy rain, so whether Little River Lake is safe to swim in today is a call for Iowa's water agency and the county health department; check their current beach advisories before you swim.
What is the water temperature of Little River Lake?
- Little River Lake typically sits around 76°F at the surface in September, from 31 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Little River Lake?
- No published bathymetric survey covers Little River Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 44 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 787 acres.
Are there boat ramps on Little River Lake?
- Little River Lake has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Little River, Little River, Little River Recreatioal Park. Public access is listed as yes.
Can I fish at Little River Lake?
- Little River Lake has 3 documented boat landings 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 Little River Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at Iowa's top lakes, each with its readings
Iowa's cleanest lakes, ranked on agency measurements
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Other Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
53 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_WQX53 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)
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
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