Mountain Run Lake
Culpeper County, Virginia75 acresView mapDirections
Nutrients and algae run above the regional average.
↓ down from C at the last regrade
- Eutrophic
- Impaired · Pathogens (E. coli, fecal)
- #1 of 2 in the county
- 37 ft max depth
- Public access
Mountain Run Lake in Culpeper County, Virginia has a water quality grade of D (Nutrient-rich). Water clarity: 2.6 ft visibility. Phosphorus: 40 µg/L. Chlorophyll-a (algae): 17.3 µg/L. Surface area: 75 acres.
- Clarity
- 2.6 ft
- Max depth
- ~37 ft est.
- Area
- 75 acres
- Type
- Eutrophic
- Phosphorus
- 40 µg/L
- Chlorophyll-a
- 17.3 µg/L
- Trend
- ↓ Declining
- Public access
- Yes
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Stays near Mountain Run Lake
Compare lakeside cabins, hotels, and vacation rentals near Mountain Run Lake in Culpeper County, Virginia — 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 grade measures nutrients and algae, not lodging — cabins and rentals around Mountain Run Lake are listed below.
Top-rated places to stay near Mountain Run Lake
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Watch Mountain Run Lake’s letter
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Mountain Run Lake is a 75-acre productive, nutrient-rich eutrophic lake in Culpeper County, Virginia with an estimated average depth of about 37 feet. Water quality is graded D based on 2 sampling years through 2022. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 1 other monitored lakes in Culpeper County, Mountain Run Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Virginia DEQ, last sampled 2022-10-06. Grade methodology: LakeQuality methodology.
What Mountain Run Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Grade onlyBacteria advisory
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.
The D is nutrients and algae, not a swimming clearance. Mountain Run Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for pathogens (E. coli, fecal). Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 2.6 ft of visibility. Phosphorus 40 µg/L. Chlorophyll-a 17.3 µg/L. TSI 60. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | Not graded |
| Phosphorus | 40 µg/L | Poor |
| Chlorophyll-a (Algae) | 17.3 µg/L | Poor |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~37 ft est. |
| Average Depth | ~11 ft est. |
| Surface Area | 75 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Virginia has not published bathymetry for Mountain Run Lake.
Lake Size & Watershed
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
- Mountain Run LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Mountain Run Lake
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.033 m/yr | 4 |
| Phosphorus | ↓ Declining | +1.1 µg/L/yr | 4 |
| Chlorophyll-a | ↓ Declining | +1.11 µg/L/yr | 4 |
Reservoir Info (USACE NID)
Mountain Run Lake is a man-made reservoir impounded by the Mountain Run Dam #11, built primarily for flood risk reduction on the Mountain Run; earth-type dam, 44 ft tall and 722 ft long.
- Surface area
- 75 ac
- Normal storage
- 611 ac-ft
- Max storage
- 2,880 ac-ft
- Drainage area
- 6.46 sq mi
- Hazard class
- High
- Owner
- Town of Culpeper
All listed purposes: Flood Risk Reduction;Water Supply.
Source: USACE National Inventory of Dams, NID ID VA047002 · Operator website
EPA Impairment Status
Mountain Run Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit VAN-E09L_MTN02A02 · Official waterbody report
County Ranking
Ranked #1 of 2 lakes in Culpeper County
Nearby Lakes With Higher Grades
Mountain Run Lake holds Grade D. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Culpeper County
Frequently asked questions about Mountain Run Lake
Where is Mountain Run Lake?
- Mountain Run Lake is a lake in Culpeper County, Virginia. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Mountain Run Lake?
- Mountain Run Lake in Culpeper County, Virginia has a water quality grade of D (Nutrient-rich). Water clarity: 2.6 ft visibility. Phosphorus: 40 µg/L. Chlorophyll-a (algae): 17.3 µg/L. Surface area: 75 acres.
Is Mountain Run Lake safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Mountain Run Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for pathogens (E. coli, fecal). Check local advisories before you swim.
How deep is Mountain Run Lake?
- No published bathymetric survey covers Mountain Run Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 37 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 75 acres.
Are there boat ramps on Mountain Run Lake?
- Mountain Run Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Mountain Run Lake. Public access is listed as yes.
Explore Mountain Run Lake across LakeQuality
2 documented falls within 20.5 mi, nearest Dark Hollow Falls
Species activity outlook by water temperature and season
Where to stay at Virginia's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Virginia's cleanest and most-polluted lakes, ranked
Planning a trip around Shenandoah?
Mountain Run Lake is about 22 miles from Shenandoah National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Shenandoah →More Virginia Lake Rankings
Other Grade D Lakes in Virginia
Eutrophic Lakes in Virginia
Where this data comes from
207 measurements from 2 monitoring stations, 2014–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- VIRGINIA DEPARTMENT OF ENVIRONMENTAL QUALITY
21VASWCB207 samples · 2014–2022
Analytical methods
- Tyler, John. 1968. The secchi disk, Limnology and Oceanograpy, 13(1):1-6.
- Total Phosphorus After Block Digestion
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory