Lake Blackshear
Crisp County, Georgia8,700 acresView mapDirections
Clarity, phosphorus, and algae sit in the clean band for this region.
↑ up from C at the last regrade
- Eutrophic
- #1 of 1 in the county
Lake Blackshear in Crisp County, Georgia has a water quality grade of B (Good). Water clarity: 3.9 ft visibility. Phosphorus: 30.5 µg/L. Chlorophyll-a (algae): 12.5 µg/L. Surface area: 8700 acres.
- Clarity
- 3.9 ft
- Area
- 8,700 acres
- Type
- Eutrophic
- Phosphorus
- 30.5 µg/L
- Chlorophyll-a
- 12.5 µg/L
- Trend
- ↓ Declining
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Stays near Lake Blackshear
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Watch Lake Blackshear’s letter
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Lake Blackshear is a 8,700-acre productive, nutrient-rich eutrophic lake in Crisp County, Georgia. Water quality is graded B based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, Georgia EPD, last sampled 2025-10-27. Grade methodology: LakeQuality methodology.
What Lake Blackshear is good for
From access and monitoring records, not editorial picks.
- Big water8,700 acres
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.
The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: B (Good)
Murky, only visible to about 3.9 ft. Phosphorus 30.5 µg/L. Chlorophyll-a 12.5 µg/L. TSI 55. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | Not graded |
| Phosphorus | 30.5 µg/L | Good |
| Chlorophyll-a (Algae) | 12.5 µg/L | Good |
| Trophic State Index (TSI) | 55 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 8,700 acres |
No bathymetric survey has been published for Lake Blackshear, so its depth is not documented here.
Fishing Lake Blackshear
Water Quality Trend: ↓ Declining
Based on 14 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.02 m/yr | 14 |
| Phosphorus | → Stable | -0.26 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +0.63 µg/L/yr | 14 |
Reservoir Info (USACE NID)
Lake Blackshear is a man-made reservoir impounded by the Crisp County (Warwick) (completed 1930), built primarily for hydroelectric on the Flint; gravity-type dam, 50 ft tall and 4,500 ft long.
- Surface area
- 8,700 ac
- Normal storage
- 145,000 ac-ft
- Max storage
- 160,000 ac-ft
- Drainage area
- 3,750 sq mi
- Hazard class
- High
- Owner
- Crisp County Power Commission
Source: USACE National Inventory of Dams, NID ID GA00719 · Operator website
County Ranking
Ranked #1 of 1 lakes in Crisp County
Nearby Lakes With Higher Grades
Lake Blackshear holds Grade B. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Crisp County
Frequently asked questions about Lake Blackshear
Where is Lake Blackshear?
- Lake Blackshear is a lake in Crisp County, Georgia. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Blackshear?
- Lake Blackshear in Crisp County, Georgia has a water quality grade of B (Good). Water clarity: 3.9 ft visibility. Phosphorus: 30.5 µg/L. Chlorophyll-a (algae): 12.5 µg/L. Surface area: 8700 acres.
Is Lake Blackshear safe to swim in?
- The B is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Explore Lake Blackshear across LakeQuality
More Georgia Lake Rankings
Other Grade B Lakes in Georgia
Eutrophic Lakes in Georgia
Where this data comes from
260 measurements from 1 monitoring station, 2012–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Georgia DNR Environmental Protection Division
21GAEPD_WQX260 samples · 2012–2025
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
- Turbidity by Nephelometry
- 2120 B ~ Color in Water by Visual Comparison
Monitoring station identifiers (1)
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.