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. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-08-26. Grade methodology: LakeGrade methodology.
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Swimming Safety
Based on E. coli testing, Lake Darling Max Depth routinely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 40.4% of 109 samples across 7 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, Very Poor
Very murky, less than 1.6 ft of visibility. Chlorophyll-a: 60.5 µg/L. Trophic State Index: 71.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 60.5 µg/L | F |
| Trophic State Index (TSI) | 71 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 304 acres |
| Public Access | Yes |
Where to stay 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.
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Fishing Lake Darling Max Depth
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.081 m/yr | 4 |
| Chlorophyll-a | → Stable | +0.69 µg/L/yr | 4 |
Recreation & Access
Water Temperature
Lake Darling Max Depth averages about 78°F at the surface in summer, 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 →
Location & Depth Map
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.
County Ranking
Ranked #1 of 1 lakes in Washington County
Cleaner Lakes Within 30 Miles
Lake Darling Max Depth holds Grade F. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Washington County
Explore Lake Darling Max Depth across LakeGrade
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Hypereutrophic Lakes in Iowa
More records, surveys & data sources
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)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-08-26
Monitoring stations: 1