Lake Monroe
Union County, North Carolina118 acresView mapDirections
NC DEQ publishes the water-quality measurements for Lake Monroe. Here is what has been measured.
- Hypereutrophic
- Impaired · Algal growth
- 34 ft max depth
- Limited data
Lake Monroe in Union County, North Carolina has water-quality measurements published by NC DEQ, shown here as reported. Phosphorus: 110 µg/L. Chlorophyll-a (algae): 62 µg/L. Surface area: 118 acres.
Lake Monroe is a 118-acre highly nutrient-loaded hypereutrophic lake in Union County, North Carolina with an estimated average depth of about 34 feet. Compared to the 2 other monitored lakes in Union County, Lake Monroe ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, NCDEQ, last sampled 2021-09-29. Methodology: how these readings are compared.
Lake Monroe covers about 120 acres in Union County. Vrbo is where to look for cabins and lake homes around Lake Monroe, and Booking.com and Expedia search hotels near the lake for your dates.
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Lake Monroe is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
Whether Lake Monroe is safe to swim in today is a call for the North Carolina Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Lake Monroe
These are the measurements NC DEQ publishes for Lake Monroe, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 110 µg/L. Chlorophyll-a 62 µg/L. TSI 72.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 110µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 62µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 72 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Lake Monroe
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~34 ft est.
Surface area
118 acres
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. North Carolina has not published bathymetry for Lake Monroe.
Lake Size & Watershed
Watershed (drainage) area
10 sq mi
HydroLAKES / HydroSHEDS
Shoreline
2 mi
HydroLAKES / HydroSHEDS
Elevation
548 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Stays via Stay22
Stays near Lake Monroe
Compare lakeside cabins, hotels, and vacation rentals near Lake Monroe in Union County, North Carolina — 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Lake Monroe are listed below.
Top-rated places to stay near Lake Monroe
Prices for Oct 23–25, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at North Carolina’s top lakes →
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Fishing Lake Monroe
Reservoir Info (USACE NID)
Lake Monroe is a man-made reservoir impounded by the Lake Monroe Dam (completed 1955), built primarily for recreation on the Richardson Creek; earth-type dam, 46 ft tall and 770 ft long.
- Surface area
- 118 ac
- Normal storage
- 1,765 ac-ft
- Max storage
- 2,721 ac-ft
- Drainage area
- 9.58 sq mi
- Hazard class
- High
- Owner
- City of Monroe
All listed purposes: Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID NC00535 · Operator website
EPA Impairment Status
Lake Monroe is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NC13-17-36-4-(0.5) · Official waterbody report
Nearby Lakes in Union County
Frequently asked questions about Lake Monroe
Where is Lake Monroe?
- Lake Monroe is a lake in Union County, North Carolina. Its water-quality measurements are published by NC DEQ and shown on this page as reported.
What is the water quality of Lake Monroe?
- Lake Monroe in Union County, North Carolina has water-quality measurements published by NC DEQ, shown here as reported. Phosphorus: 110 µg/L. Chlorophyll-a (algae): 62 µg/L. Surface area: 118 acres.
Is Lake Monroe safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake Monroe is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
How deep is Lake Monroe?
- No published bathymetric survey covers Lake Monroe, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 34 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 118 acres.
Explore Lake Monroe across LakeQuality
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Where this data comes from
27 measurements from 2 monitoring stations, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Carolina Dept of Environmental Quality NCDEQ-DWR WQX
21NC03WQ27 samples · 2021
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 2130 B ~ Nephelometric Method
Monitoring station identifiers (2)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)