Don Williams Lake is a 160-acre productive, nutrient-rich eutrophic lake in Boone 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 2 public boat landings.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-09-04. Grade methodology: LakeGrade methodology.
Watch Don Williams Lake water quality
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Swimming Safety
Based on E. coli testing, Don Williams Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 20% of 10 samples across 3 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 1.8 ft of visibility. Chlorophyll-a: 45.2 µg/L. Trophic State Index: 68.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 45.2 µg/L | F |
| Trophic State Index (TSI) | 68 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 160 acres |
| Public Access | Yes |
Where to stay near Don Williams Lake
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Fishing Don Williams Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.005 m/yr | 5 |
| Chlorophyll-a | ↓ Declining | +4.72 µg/L/yr | 5 |
Recreation & Access
Water Temperature
Don Williams Lake averages about 74°F at the surface in summer, usually warmest in Aug (about 76°F) and coldest in May (about 62°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 Don Williams Lake water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Don Williams Lake, reaching a maximum surveyed depth of 36 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #1 of 1 lakes in Boone County
Cleaner Lakes Within 30 Miles
Don Williams Lake holds Grade F. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Boone County
Explore Don Williams Lake across LakeGrade
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Other Grade F Lakes in Iowa
Eutrophic Lakes in Iowa
More records, surveys & data sources
Reservoir Info (USACE NID)
Don Williams Lake is a man-made reservoir impounded by the Don Williams Lake Dam (completed 1965), built primarily for recreation on the BLUFF CREEK; earth-type dam, 58 ft tall and 600 ft long.
- Surface area
- 160 ac
- Normal storage
- 2,764 ac-ft
- Max storage
- 4,680 ac-ft
- Drainage area
- 33 sq mi
- Hazard class
- Significant
- Owner
- Boone County Conservation Board
Source: USACE National Inventory of Dams, NID ID IA00134 · Operator website
EPA Impairment Status
Don Williams Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 04-UDM-1249 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
4 EPA-permitted facilities operate within about 5 miles of Don Williams Lake under Clean Water Act (NPDES) discharge permits. 3 facilities have a reported Clean Water Act violation in the past three years.
- Pilot Mound City Of StpPilot Mound · 2.8 mi away · NPDES IA0058530Recent violation
- Northern Natural Gas Co. Ogden StationOgden · 4.7 mi away · NPDES IA0046957Recent violation
- Boone, City Of WtpBoone · 5 mi away · NPDES IA0079421Recent violation
- Ymca Camp Of BooneBoone · 4.4 mi away · NPDES IA0070874
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.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
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: 2024-09-04
Monitoring stations: 1