Black Cnyn Reservoir Ns of
Gem County, Idaho1,100 acresView mapDirections
Idaho DEQ publishes the water-quality measurements for Black Cnyn Reservoir Ns of. Here is what has been measured.
- Mesotrophic
- Public access
Black Cnyn Reservoir Ns of in Gem County, Idaho has water-quality measurements published by Idaho DEQ, shown here as reported. Water clarity: 7.5 ft visibility. Phosphorus: 29.5 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Surface area: 1100 acres.
Black Cnyn Reservoir Ns of is a 1,100-acre mesotrophic lake in Gem County, Idaho. Water clarity is improving over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 1 other monitored lakes in Gem County, Black Cnyn Reservoir Ns of ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, IDEQ, last sampled 2023-08-17. Methodology: how these readings are compared.
What Black Cnyn Reservoir Ns of is good for
From access and monitoring records, not editorial picks.
- Big water1,100 acres
Swimming conditions
Readings onlyLow algae
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 Black Cnyn Reservoir Ns of is safe to swim in today is a call for the Idaho Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Black Cnyn Reservoir Ns of
These are the measurements Idaho DEQ publishes for Black Cnyn Reservoir Ns of, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 7.5 ft. Phosphorus 29.5 µg/L. Chlorophyll-a 3.1 µg/L. TSI 48.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 29.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 3.1µg/L | Good 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 Black Cnyn Reservoir Ns of
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
1,100 acres
Public access
Yes
Listed by Idaho DEQ
No bathymetric survey has been published for Black Cnyn Reservoir Ns of, so its depth is not documented here.
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Fishing Black Cnyn Reservoir Ns of
Water Quality Trend: Stable
Based on 6 years of monitoring (2012–2023).
Water clarity
Improving5 years
Phosphorus
Stable-0.19 µg/L/yr6 years
Chlorophyll-a
Worsening+0.34 µg/L/yr5 years
Reservoir Info (USACE NID)
Black Cnyn Reservoir Ns of is a man-made reservoir impounded by the Black Canyon Diversion Dam (completed 1924), built primarily for hydroelectric on the Payette River; concrete-type dam, 183 ft tall and 1,039 ft long.
- Surface area
- 1,100 ac
- Normal storage
- 29,822 ac-ft
- Max storage
- 31,200 ac-ft
- Drainage area
- 2,680 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Hydroelectric;Irrigation.
Source: USACE National Inventory of Dams, NID ID ID00282 · Operator website · Matched by proximity (0.52 km)
Nearby Lakes in Gem County
Frequently asked questions about Black Cnyn Reservoir Ns of
Where is Black Cnyn Reservoir Ns of?
- Black Cnyn Reservoir Ns of is a lake in Gem County, Idaho. Its water-quality measurements are published by Idaho DEQ and shown on this page as reported.
What is the water quality of Black Cnyn Reservoir Ns of?
- Black Cnyn Reservoir Ns of in Gem County, Idaho has water-quality measurements published by Idaho DEQ, shown here as reported. Water clarity: 7.5 ft visibility. Phosphorus: 29.5 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Surface area: 1100 acres.
Is Black Cnyn Reservoir Ns of safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Can I fish at Black Cnyn Reservoir Ns of?
- Public access to Black Cnyn Reservoir Ns of is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Idaho's fish and wildlife agency, so check its current regulations before you go.
Explore Black Cnyn Reservoir Ns of across LakeQuality
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Where this data comes from
36 measurements from 1 monitoring station, 2012–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Bureau of Reclamation
1119USBR_WQX36 samples · 2012–2023
Analytical methods
- Depth, Secchi disk depth
- Zebra/Quagga Mussel APHA 10200G Modified
- Phosphorus by Single Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
Monitoring station identifiers (1)
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.