Monroe-Northside Lake
Monroe-Northside Lake in Monroe County, Florida has a water quality grade of B (Good). Water clarity: 3.9 ft visibility. Phosphorus: 23.5 µg/L.
- Clarity
- 3.9 ft
- Type
- Eutrophic
- Trend
- → Stable
- Public access
- Yes
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Monroe-Northside Lake is a productive, nutrient-rich eutrophic lake in Monroe County, Florida. Water quality is graded B based on 1 sampling years through 2024. Water clarity is declining over recent sampling years. Limited fish-species data available. Public access is available with 4 public boat landings. Compared to the 1 other monitored lakes in Monroe County, Monroe-Northside Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2024-12-06. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
Murky, only visible to about 3.9 ft. Phosphorus level: 23.5 µg/L. Trophic State Index: 54.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | Not graded |
| Phosphorus | 23.5 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 54 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Monroe-Northside Lake
Compare lakeside cabins, hotels, and vacation rentals near Monroe-Northside Lake in Monroe County, Florida — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Monroe-Northside Lake
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Recreation & Access
- Key West City Marina at Garrison BightPublic
- City of Key West 11th Street Public Boat RampPublic
- Oceanside Marina of Stock IslandSemi-private
- Key West Yacht ClubSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Monroe-Northside Lake
Water Quality Trend: → Stable
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.2 m/yr | 2 |
| Phosphorus | ↑ Improving | -6.15 µg/L/yr | 4 |
EPA Impairment Status
Monroe-Northside Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit FL6014B · Official waterbody report · Matched by proximity (1.04 km)
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Monroe-Northside Lake under Clean Water Act (NPDES) discharge permits.
- Adolfos Custom Boat WorkUnknown · 1.5 mi away · NPDES FLY970099
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.
County Ranking
Ranked #1 of 2 lakes in Monroe County
Nearby Lakes in Monroe County
Frequently asked questions about Monroe-Northside Lake
Where is Monroe-Northside Lake?
- Monroe-Northside Lake is a lake in Monroe County, Florida. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Monroe-Northside Lake?
- Monroe-Northside Lake in Monroe County, Florida has a water quality grade of B (Good). Water clarity: 3.9 ft visibility. Phosphorus: 23.5 µg/L.
Is Monroe-Northside Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Monroe-Northside Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
Are there boat ramps on Monroe-Northside Lake?
- Monroe-Northside Lake has 4 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Key West City Marina at Garrison Bight, City of Key West 11th Street Public Boat Ramp, Oceanside Marina of Stock Island, Key West Yacht Club. Public access is listed as yes.
Explore Monroe-Northside Lake across LakeQuality
More Florida Lake Rankings
Other Grade B Lakes in Florida
Eutrophic Lakes in Florida
Where this data comes from
52 measurements from 2 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- FLORIDA LAKEWATCH
21FLKWAT_WQX52 samples · 2020–2024
Monitoring station identifiers (2)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Named boat-access points from the USGS National Boat Ramps inventory