Greenfield Lake
Adair County, Iowa50 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Turbidity
- #3 of 5 in the county
- 39 ft max depth
Greenfield Lake in Adair County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 2.1 ft visibility. Phosphorus: 113 µg/L. Chlorophyll-a (algae): 53.8 µg/L. Surface area: 49.6 acres.
- Clarity
- 2.1 ft
- Typical in September
- 71°F
- Max depth
- ~39 ft est.
- Area
- 50 acres
- Type
- Hypereutrophic
- Phosphorus
- 113 µg/L
- Chlorophyll-a
- 53.8 µg/L
- Trend
- ↓ Declining
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 grade measures nutrients and algae, not lodging — cabins and rentals around Greenfield Lake are listed below.
Top-rated places to stay near Greenfield Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
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Watch Greenfield Lake’s letter
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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. Water quality is graded F based on 2 sampling years through 2024. 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. Grade methodology: LakeQuality methodology.
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 F is nutrients and algae, not a swimming clearance. Greenfield Lake is listed impaired under Clean Water Act §303(d) (IR 5) for turbidity. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 2.1 ft of visibility. Phosphorus 113 µg/L. Chlorophyll-a 53.8 µg/L. TSI 70. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.1 ft | Not graded |
| Phosphorus | 113 µg/L | Poor |
| Chlorophyll-a (Algae) | 53.8 µg/L | Poor |
| Trophic State Index (TSI) | 70 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
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.
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
| Characteristic | Value |
|---|---|
| Maximum Depth | ~39 ft est. |
| Average Depth | ~14 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
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.
Fishing Greenfield Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.009 m/yr | 5 |
| Phosphorus | ↓ Declining | +16 µg/L/yr | 4 |
| Chlorophyll-a | ↓ Declining | +2.9 µg/L/yr | 5 |
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
EPA Impairment Status
Greenfield Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IA 05-NOD-1401 · Official waterbody report · Matched by proximity (1.55 km)
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.
County Ranking
Ranked #3 of 5 lakes in Adair County
Nearby Lakes With Higher Grades
Greenfield Lake holds Grade F. 2 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 Adair County
Frequently asked questions about Greenfield Lake
Where is Greenfield Lake?
- Greenfield Lake is a lake in Adair County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Greenfield Lake?
- Greenfield Lake in Adair County, Iowa has a water quality grade of F (Algae-prone). 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?
- The F is nutrients and algae, not a swimming clearance. Greenfield Lake is listed impaired under Clean Water Act §303(d) (IR 5) for turbidity. 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
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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)
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)