Base Line Lake
Washtenaw County, Michigan251 acresView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Impaired · Mercury
- Limited data
Base Line Lake in Washtenaw County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 11 ft visibility. Surface area: 251.4 acres.
- Clarity
- 11 ft
- Area
- 251 acres
- Trend
- ↓ Declining
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Watch Base Line Lake’s letter
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Why Base Line Lake has no grade
Base Line Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Base Line Lake is Not Rated — not an F. Its 11-foot median from 108 readings collected 2016–2024 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by EGLE and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Base Line Lake is a 251-acre lake in Washtenaw County, Michigan. Overall water quality is declining over recent sampling years. The lake supports 1 documented fish species including Brindled madtom.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2024-07-11. Grade methodology: LakeQuality methodology.
What Base Line Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11 ft of visibility
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Base Line Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pesticides, pFAS. Check local advisories before you swim.
Water quality measurements for Base Line Lake
These readings exist but are not enough for an A–F grade — see why.
Good clarity, visible to about 11 ft. TSI 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 251 acres |
No bathymetric survey has been published for Base Line Lake, so its depth is not documented here.
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Base Line Lake
Water Quality Trend: ↓ Declining
Based on 9 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.172 m/yr | 9 |
| Phosphorus | ↓ Declining | +1.24 µg/L/yr | 7 |
EPA Impairment Status
Base Line 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 MI040900050307-11 · Official waterbody report
Graded lakes near Base Line Lake
Base Line Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Washtenaw County
Frequently asked questions about Base Line Lake
Where is Base Line Lake?
- Base Line Lake is a lake in Washtenaw County, Michigan. LakeQuality has not rated this lake (UNRATED) — the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity.
What is the water quality grade for Base Line Lake?
- Base Line Lake in Washtenaw County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 11 ft visibility. Surface area: 251.4 acres.
Is Base Line Lake safe to swim in?
- The letter is not a swimming clearance. Base Line Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pesticides, pFAS. Check local advisories before you swim.
What fish are in Base Line Lake?
- Fish species found in Base Line Lake include Brindled madtom. Base Line Lake is located in Washtenaw County, Michigan.
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Where this data comes from
108 measurements from 1 monitoring station, 2016–2024. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- North American Lake Management Society
NALMS108 samples · 2016–2024
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database