Lake Darling Max Depth
Washington County, Iowa304 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Algal growth
- #1 of 1 in the county
- Public access
Lake Darling Max Depth in Washington County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 226 µg/L. Chlorophyll-a (algae): 60.5 µg/L. Surface area: 304 acres.
- Clarity
- 1.6 ft
- Typical in September
- 69°F
- Area
- 304 acres
- Type
- Hypereutrophic
- Trend
- → Stable
- Public access
- Yes
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Stays near Lake Darling Max Depth
Compare lakeside cabins, hotels, and vacation rentals near Lake Darling Max Depth in Washington 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 Lake Darling Max Depth are listed below.
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Free interactive depth-contour map of Lake Darling Max Depth, reaching a maximum surveyed depth of 18 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
Lake Darling Max Depth is a 304-acre highly nutrient-loaded hypereutrophic lake in Washington County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Water clarity is declining over recent sampling years. Limited fish-species data available. Public access is available.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-08-26. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyBacteria A · advisory
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.
Based on E. coli testing, Lake Darling Max Depth never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 5 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.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.6 ft of visibility. Phosphorus 226 µg/L. Chlorophyll-a 60.5 µg/L. TSI 75. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 226 µg/L | Poor |
| Chlorophyll-a (Algae) | 60.5 µg/L | Poor |
| Trophic State Index (TSI) | 75 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Lake Darling Max Depth typically sits around 69°F at the surface in September. Summer average is about 78°F. Usually warmest in Jun (about 79°F) and coldest in Sep (about 69°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 17 field readings (2015–2023) via the EPA Water Quality Portal. See the full Lake Darling Max Depth water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 304 acres |
| Public Access | Yes |
No bathymetric survey has been published for Lake Darling Max Depth, so its depth is not documented here.
Fishing Lake Darling Max Depth
Water Quality Trend: → Stable
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.081 m/yr | 4 |
| Phosphorus | ↑ Improving | -5.1 µg/L/yr | 4 |
| Chlorophyll-a | → Stable | +0.69 µg/L/yr | 4 |
Reservoir Info (USACE NID)
Lake Darling Max Depth is a man-made reservoir impounded by the Lake Darling Dam (completed 1950), built primarily for recreation on the HONEY CREEK; earth-type dam, 47 ft tall and 1,230 ft long.
- Surface area
- 304 ac
- Normal storage
- 3,154 ac-ft
- Max storage
- 9,823 ac-ft
- Drainage area
- 19.64 sq mi
- Hazard class
- Significant
- Owner
- Iowa Department of Natural Resources
Source: USACE National Inventory of Dams, NID ID IA01381 · Operator website · Matched by proximity (0.2 km)
EPA Impairment Status
Lake Darling Max Depth is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 03-SKU-924 · Official waterbody report · Matched by proximity (1.1 km)
County Ranking
Ranked #1 of 1 lakes in Washington County
Nearby Lakes With Higher Grades
Lake Darling Max Depth holds Grade F. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Washington County
Frequently asked questions about Lake Darling Max Depth
Where is Lake Darling Max Depth?
- Lake Darling Max Depth is a lake in Washington County, Iowa. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Darling Max Depth?
- Lake Darling Max Depth in Washington County, Iowa has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 226 µg/L. Chlorophyll-a (algae): 60.5 µg/L. Surface area: 304 acres.
Is Lake Darling Max Depth safe to swim in?
- Based on E. coli testing, Lake Darling Max Depth never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 5 samples across 2 seasons. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Lake Darling Max Depth has a water quality grade of F (Algae-prone). Bacteria levels can spike quickly after heavy rain, so always check Iowa's current beach and health-department advisories before you swim.
What is the water temperature of Lake Darling Max Depth?
- Lake Darling Max Depth typically sits around 69°F at the surface in September, from 17 EPA Water Quality Portal field readings (2015–2023). That is a typical value for the month, not a live reading.
Explore Lake Darling Max Depth 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 grade
Very high nutrients, dense algae, poor clarity
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Where this data comes from
54 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_WQX54 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)
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