Rocky River Reservoir
Chatham County, North Carolina100 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- #6 of 7 in the county
- 43 ft max depth
- Limited data
Rocky River Reservoir in Chatham County, North Carolina has a water quality grade of F (Algae-prone). Water clarity: 1.9 ft visibility. Phosphorus: 55 µg/L. Chlorophyll-a (algae): 55.5 µg/L. Surface area: 100 acres.
- Clarity
- 1.9 ft
- Max depth
- ~43 ft est.
- Area
- 100 acres
- Type
- Hypereutrophic
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Stays near Rocky River Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Rocky River Reservoir in Chatham 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 grade measures nutrients and algae, not lodging — cabins and rentals around Rocky River Reservoir are listed below.
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Rocky River Reservoir is a 100-acre highly nutrient-loaded hypereutrophic lake in Chatham County, North Carolina with an estimated average depth of about 43 feet. Water quality is graded F based on 2 sampling years through 2023. Compared to the 6 other monitored lakes in Chatham County, Rocky River Reservoir ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, NCDEQ, last sampled 2023-09-21. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLimited data
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 F is nutrients and algae, not a swimming clearance. Rocky River Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.9 ft of visibility. Phosphorus 55 µg/L. Chlorophyll-a 55.5 µg/L. TSI 67. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.9 ft | Not graded |
| Phosphorus | 55 µg/L | Poor |
| Chlorophyll-a (Algae) | 55.5 µg/L | Poor |
| Trophic State Index (TSI) | 67 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~43 ft est. |
| Average Depth | ~12 ft est. |
| Surface Area | 100 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 Rocky River Reservoir.
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.
Fishing Rocky River Reservoir
Reservoir Info (USACE NID)
Rocky River Reservoir is a man-made reservoir impounded by the Rocky River Reservoir Dam (completed 1961), built primarily for other on the Rocky River; earth-type dam, 30 ft tall and 730 ft long.
- Surface area
- 100 ac
- Normal storage
- 403 ac-ft
- Max storage
- 500 ac-ft
- Drainage area
- 53.8 sq mi
- Hazard class
- Low
- Owner
- Town of Siler City
All listed purposes: Other;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID NC00616 · Operator website
EPA Impairment Status
Rocky River Reservoir 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 NC17-43-(5.5)a · Official waterbody report
County Ranking
Ranked #6 of 7 lakes in Chatham County
Nearby Lakes With Higher Grades
Rocky River Reservoir holds Grade F. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Chatham County
Frequently asked questions about Rocky River Reservoir
Where is Rocky River Reservoir?
- Rocky River Reservoir is a lake in Chatham County, North Carolina. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Rocky River Reservoir?
- Rocky River Reservoir in Chatham County, North Carolina has a water quality grade of F (Algae-prone). Water clarity: 1.9 ft visibility. Phosphorus: 55 µg/L. Chlorophyll-a (algae): 55.5 µg/L. Surface area: 100 acres.
Is Rocky River Reservoir safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Rocky River Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
How deep is Rocky River Reservoir?
- No published bathymetric survey covers Rocky River Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 43 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 100 acres.
Explore Rocky River Reservoir across LakeQuality
Species activity outlook by water temperature and season
Where to stay at North Carolina's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
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Where this data comes from
41 measurements from 2 monitoring stations, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North Carolina Dept of Environmental Quality NCDEQ-DWR WQX
21NC03WQ41 samples · 2023
Analytical methods
- WSSSOP
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- 2130 B ~ Nephelometric Method
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)