Briggs Woods Lake is a 70-acre highly nutrient-loaded hypereutrophic lake in Hamilton County, Iowa. Water quality is graded F based on 2 sampling years through 2024. Water clarity is improving over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 1 other monitored lakes in Hamilton County, Briggs Woods Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Iowa DNR, last sampled 2024-10-30. Grade methodology: LakeGrade methodology.
Watch Briggs Woods Lake water quality
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.5 ft of visibility. Chlorophyll-a: 59.1 µg/L. Trophic State Index: 71.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.5 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 59.1 µg/L | F |
| Trophic State Index (TSI) | 71 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 70 acres |
| Public Access | Yes |
Where to stay near Briggs Woods Lake
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Fishing Briggs Woods Lake
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.072 m/yr | 5 |
| Chlorophyll-a | ↓ Declining | +3.97 µg/L/yr | 5 |
Recreation & Access
Water Temperature
Briggs Woods Lake averages about 77°F at the surface in summer, usually warmest in Jul (about 82°F) and coldest in May (about 61°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 32 field readings (2010–2023) via the EPA Water Quality Portal. See the full Briggs Woods Lake water temperature breakdown →
Location & Depth Map
Free interactive depth-contour map of Briggs Woods Lake, reaching a maximum surveyed depth of 26 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Iowa DNR.
County Ranking
Ranked #1 of 2 lakes in Hamilton County
Cleaner Lakes Within 30 Miles
Briggs Woods Lake holds Grade F. 2 nearby lakes hold higher grades.
- BAda Hayden Heritage Park LakeStory County · 26.8 mi · Two grade letters higher (F → B)
- DLake CorneliaWright County · 25.4 mi · Higher grade (F → D)
Nearby Lakes in Hamilton County
Explore Briggs Woods Lake across LakeGrade
More Iowa Lake Rankings
Other Grade F Lakes in Iowa
Hypereutrophic Lakes in Iowa
More records, surveys & data sources
Reservoir Info (USACE NID)
Briggs Woods Lake is a man-made reservoir impounded by the Briggs Woods Lake Dam (completed 1968), built primarily for recreation on the TR-BOONE RIVER; earth-type dam, 44 ft tall and 3,100 ft long.
- Surface area
- 70 ac
- Normal storage
- 1,310 ac-ft
- Max storage
- 2,100 ac-ft
- Drainage area
- 10.62 sq mi
- Hazard class
- Significant
- Owner
- Hamilton County Conservation Board
All listed purposes: Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IA00437 · Operator website
EPA Impairment Status
Briggs Woods Lake 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 04-UDM-1255 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Briggs Woods Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 3 facilities have a reported Clean Water Act violation in the past three years.
- Webster City, City Of StpWebster City · 1.8 mi away · NPDES IA0036625MajorRecent violation
- Webster City Municipal Bldg.Webster City · 2.7 mi away · NPDES IA0066281Recent violation
- Kamrar City Of StpKamrar · 4.7 mi away · NPDES IA0069124Recent violation
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: 2024-10-30
Monitoring stations: 1