Greenfield Lake
Adair County, Iowa50 acresView mapDirections
Iowa DNR publishes the water-quality measurements for Greenfield Lake. Here is what has been measured.
- Hypereutrophic
- 39 ft max depth
Greenfield Lake in Adair County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.1 ft visibility. Phosphorus: 113 µg/L. Chlorophyll-a (algae): 53.8 µg/L. Surface area: 49.6 acres.
Free interactive depth-contour map of Greenfield Lake, reaching a maximum surveyed depth of 24 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Greenfield Lake is a 50-acre highly nutrient-loaded hypereutrophic lake in Adair County, Iowa with an estimated average depth of about 39 feet. Overall water quality is declining over recent sampling years. Compared to the 4 other monitored lakes in Adair County, Greenfield Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-29. 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. Check local advisories before you swim.
Whether Greenfield 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 Greenfield Lake
These are the measurements Iowa DNR publishes for Greenfield 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 2.1 ft of visibility. Phosphorus 113 µg/L. Chlorophyll-a 53.8 µg/L. TSI 70.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 113µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 53.8µg/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. | 70 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Greenfield Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Greenfield Lake typically sits around 71°F at the surface in September. Summer average is about 78°F. Usually warmest in Jul (about 81°F) and coldest in Sep (about 71°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (71°F) to its warmest (81°F).
Typical surface water temperature by month, from 29 field readings (2010–2023) via the EPA Water Quality Portal. See the full Greenfield Lake water temperature breakdown →
Lake Details
Max depth
~39 ft est.
Surface area
50 acres
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Iowa has not published bathymetry for Greenfield Lake.
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Shoreline
1.4 mi
HydroLAKES / HydroSHEDS
Elevation
1,250 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.
Stays via Stay22
Stays near Greenfield Lake
Compare lakeside cabins, hotels, and vacation rentals near Greenfield Lake in Adair 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 Greenfield Lake are listed below.
Top-rated places to stay near Greenfield Lake
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Fishing Greenfield Lake
Water Quality Trend: Worsening
Based on 5 years of monitoring (2020–2024).
Water clarity
Stable5 years
Phosphorus
Worsening+16 µg/L/yr4 years
Chlorophyll-a
Worsening+2.9 µg/L/yr5 years
Reservoir Info (USACE NID)
Greenfield Lake is a man-made reservoir impounded by the Greenfield Reservoir Dam (completed 1979), built primarily for water supply on the TR- MIDDLE NODAWAY R.; earth-type dam, 42 ft tall and 990 ft long.
- Surface area
- 49.6 ac
- Normal storage
- 612 ac-ft
- Max storage
- 1,150 ac-ft
- Drainage area
- 1.5 sq mi
- Hazard class
- High
- Owner
- Greenfield Municipal Utilities
Source: USACE National Inventory of Dams, NID ID IA02267 · Operator website
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Greenfield Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger.
- Greenfield City Of StpGreenfield · 1.3 mi away · NPDES IA0021369Major
- Greenfield Municipal Utilities WtpGreenfield · 0.3 mi away · NPDES IA0048453
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 Adair County
Frequently asked questions about Greenfield Lake
Where is Greenfield Lake?
- Greenfield Lake is a lake in Adair County, Iowa. Its water-quality measurements are published by Iowa DNR and shown on this page as reported.
What is the water quality of Greenfield Lake?
- Greenfield Lake in Adair County, Iowa has water-quality measurements published by Iowa DNR, shown here as reported. Water clarity: 2.1 ft visibility. Phosphorus: 113 µg/L. Chlorophyll-a (algae): 53.8 µg/L. Surface area: 49.6 acres.
Is Greenfield 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 Greenfield Lake?
- Greenfield Lake typically sits around 71°F at the surface in September, from 29 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Greenfield Lake?
- No published bathymetric survey covers Greenfield Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 39 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 49.6 acres.
Explore Greenfield Lake across LakeQuality
More lakes in Iowa
Other Lakes in Iowa
Hypereutrophic Lakes in Iowa
Where this data comes from
62 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_WQX62 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)