Mountain Island Lake
Gaston County, North Carolina3,235 acresView mapDirections
NC DEQ publishes the water-quality measurements for Mountain Island Lake. Here is what has been measured.
- Mesotrophic
- 41 ft max depth
- Public access
- Limited data
Mountain Island Lake in Gaston County, North Carolina has water-quality measurements published by NC DEQ, shown here as reported. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 6.5 µg/L. Surface area: 3235 acres.
Mountain Island Lake is a 3,235-acre mesotrophic lake in Gaston County, North Carolina with an estimated average depth of about 41 feet. Limited fish-species data available. Public access is available with 4 public boat landings. Compared to the 4 other monitored lakes in Gaston County, Mountain Island Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, NCDEQ, last sampled 2022-09-13. Methodology: how these readings are compared.
Mountain Island Lake covers about 3,200 acres in Gaston County. It has 4 public boat landings, so a lakefront rental is not the only way to get a boat on the water. If you are planning to stay, you can search lake houses and cabins around Mountain Island Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Mountain Island Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch4 documented ramps
- Big water3,235 acres
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. Check local advisories before you swim.
Whether Mountain Island Lake 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 Mountain Island Lake
These are the measurements NC DEQ publishes for Mountain Island Lake, 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 20 µg/L. Chlorophyll-a 6.5 µg/L. TSI 48.
| 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 | 20µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 6.5µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 48 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Mountain Island Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~41 ft est.
Surface area
3,235 acres
Public access
Yes
Listed by NC DEQ
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 Mountain Island Lake.
Lake Size & Watershed
Watershed (drainage) area
1,879 sq mi
HydroLAKES / HydroSHEDS
Shoreline
29.6 mi
HydroLAKES / HydroSHEDS
Elevation
666 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.
Recreation & Access
- RiverbendPublic
- LuciaPublic
- Highwy 73Public
- Mt. Isle Harbor DrivePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Mountain Island Lake
Compare lakeside cabins, hotels, and vacation rentals near Mountain Island Lake in Gaston 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.
Top-rated places to stay near Mountain Island Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
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Planning a trip? Cabins and lodging at Mountain Island Lake → · more North Carolina lake trips
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Fishing Mountain Island Lake
Reservoir Info (USACE NID)
Mountain Island Lake is a man-made reservoir impounded by the Mountain Island (completed 1923), built primarily for hydroelectric on the Catawba River; gravity-type dam, 140 ft tall and 2,375 ft long.
- Surface area
- 3,235 ac
- Normal storage
- 45,970 ac-ft
- Max storage
- 45,970 ac-ft
- Drainage area
- 1,860 sq mi
- Hazard class
- High
- Owner
- Duke Energy
All listed purposes: Hydroelectric;Water Supply.
Source: USACE National Inventory of Dams, NID ID NC00787 · Operator website
Nearby Lakes in Gaston County
Frequently asked questions about Mountain Island Lake
Where is Mountain Island Lake?
- Mountain Island Lake is a lake in Gaston 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 Mountain Island Lake?
- Mountain Island Lake in Gaston County, North Carolina has water-quality measurements published by NC DEQ, shown here as reported. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 6.5 µg/L. Surface area: 3235 acres.
Is Mountain Island Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Mountain Island Lake?
- No published bathymetric survey covers Mountain Island Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 41 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 3235 acres.
Are there boat ramps on Mountain Island Lake?
- Mountain Island Lake has 4 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Riverbend, Lucia, Highwy 73, Mt. Isle Harbor Drive. Public access is listed as yes.
Can I fish at Mountain Island Lake?
- Mountain Island Lake has 4 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by North Carolina's fish and wildlife agency, so check its current regulations before you go.
Explore Mountain Island Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Species activity outlook by water temperature and season
Where to stay at North Carolina's top lakes, each with its readings
North Carolina's cleanest lakes, ranked on agency measurements
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Other Lakes in North Carolina
Mesotrophic Lakes in North Carolina
Where this data comes from
66 measurements from 6 monitoring stations, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Carolina Dept of Environmental Quality NCDEQ-DWR WQX
21NC03WQ66 samples · 2022
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 2130 B ~ Nephelometric Method
Monitoring station identifiers (6)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory