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D

Milwaukee Harbor South Half Lake

Milwaukee County, WisconsinEutrophic

Milwaukee Harbor South Half Lake earns a D — measurements through 2025 show persistent nutrient pressure that limits clarity through the summer. Chlorophyll-a is the limiting factor: even when clarity looks acceptable, the algal community drives the grade down.

At a TSI of 56, Milwaukee Harbor South Half Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Milwaukee Harbor South Half Lake ranks 11 of 14 in Milwaukee County — at the lower end of the locally monitored distribution.

Milwaukee Harbor South Half Lake has no invasive species recorded in Wisconsin state databases as of 2025, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Milwaukee Harbor South Half Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.

Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-11-05. Grade methodology: LakeGrade methodology.

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Swimming Safety

Swimming not recommended, poor water quality with high algae risk

Water Quality Grade: D, Poor

Moderate clarity, visible to about 7.2 ft. Chlorophyll-a: 31 µg/L. Trophic State Index: 56.

MetricValueGrade
Water Clarity (Secchi Depth)7.2 ftC
PhosphorusNo data
Chlorophyll-a (Algae)31 µg/LF
Trophic State Index (TSI)56Eutrophic

High nutrients, frequent algae, reduced clarity

Water Quality Trend: Declining

Based on 6 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Declining-0.134 m/yr6
Chlorophyll-a Declining+6.84 µg/L/yr6
See year-by-year chart →

Location

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County Ranking

Ranked #11 of 14 lakes in Milwaukee County

Cleaner Lakes Within 30 Miles

Milwaukee Harbor South Half Lake holds Grade D. 5 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Milwaukee County

State Parks Near Milwaukee Harbor South Half Lake

EPA Impairment Status

Milwaukee Harbor South Half Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

Metals (other than mercury)Pathogens (E. coli, fecal)PCBs

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit WI10008753 · Official waterbody report · Matched by proximity (1.51 km)

Data Sources

Water quality data from the EPA Water Quality Portal

Impairment status from EPA ATTAINS 303(d) database

Grading methodology based on Metropolitan Council standards

Fish and recreation data from Wisconsin DNR Lakes

Most recent sample: 2025-11-05

Monitoring stations: 1

Where to stay near Milwaukee Harbor South Half Lake

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