Lamb Lake is a 56-acre mesotrophic lake in Johnson County, Indiana. Water quality is graded C based on 1 sampling years through 2023. Overall water quality is declining over recent sampling years. Compared to the 3 other monitored lakes in Johnson County, Lamb Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Indiana DNR, last sampled 2023-07-11. Grade methodology: LakeGrade methodology.
Watch Lamb Lake water quality
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Swimming Safety
Generally safe for swimming, moderate water quality
Water Quality Grade: C, Fair
Moderate clarity, visible to about 7.2 ft. Trophic State Index: 49.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.2 ft | C |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 49 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 56 acres |
Where to stay near Lamb Lake
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Fishing Lamb Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.023 m/yr | 5 |
| Chlorophyll-a | ↓ Declining | +1.1 µg/L/yr | 5 |
Location
County Ranking
Ranked #2 of 4 lakes in Johnson County
Nearby Lakes in Johnson County
Explore Lamb Lake across LakeGrade
More Indiana Lake Rankings
Other Grade C Lakes in Indiana
Mesotrophic Lakes in Indiana
More records, surveys & data sources
Reservoir Info (USACE NID)
Lamb Lake is a man-made reservoir impounded by the Lamb Lake Dam (completed 1937), built primarily for recreation on the UNNAMED TRIBUTARY BEAR CREEK; earth-type dam, 45 ft tall and 860 ft long.
- Surface area
- 56.3 ac
- Normal storage
- 1,600 ac-ft
- Max storage
- 1,600 ac-ft
- Drainage area
- 3.1 sq mi
- Hazard class
- High
- Owner
- THOMAS JOHNSON
Source: USACE National Inventory of Dams, NID ID IN00338 · Operator website
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
12 EPA-permitted facilities operate within about 5 miles of Lamb Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Trafalgar WwtpTrafalgar · 4.7 mi away · NPDES IN0040681Recent violation
- Riviera Club RenovationsIndianapolis · 1.1 mi away · NPDES INR10N641
- Brown County Water Utility Inc Phase Ii Cr 400 W, 650 S & 450 W Water Main ExteTrafalgar · 1.2 mi away · NPDES INRA00857
- Transportation And Maintenance FacilityTrafalgar · 3.1 mi away · NPDES INRA04331
- Indian Creek Elementary SchoolTrafalgar · 3.3 mi away · NPDES INR10J806
- Nhj School Corporation New Facilities And RenovationsTrafalgar · 3.5 mi away · NPDES INRA08253
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2023-07-11
Monitoring stations: 1