About JordanWatch
Rates lakes Avoid, Caution or Low Risk for harmful algal blooms.
- For swimmers, paddlers, dog owners
- Built for Jordan Lake, NC
- About 7,000 US lakes
- Free · No account · No ads
How it works
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Satellite
EPA CyAN cells/mL vs. WHO 1999/2003 levels
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EPA's CyAN project estimates cyanobacteria (the algae behind harmful blooms) from satellite images, in cells per milliliter, with pixels about 300 m wide. Under 20,000 cells/mL is Low Risk, 20,000 to 100,000 is Caution, and over 100,000 is Avoid.
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Cells, not toxins
Satellites can't measure toxins
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NC DHHS and EPA judge recreation by a toxin, microcystin (8 µg/L), which needs a water test. Satellites can't measure toxins, so JordanWatch uses WHO's cell-count levels as an early warning.
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Other signals
Rain, rivers, lake level, wind
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Heavy rain in the last 48 hours or a river running higher than usual can wash bacteria into the water, so they can raise a verdict to Caution. So can a lake well above its usual level. Light wind can pile floating algae on the downwind shore, so beaches there go up one level.
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Worst signal wins
Old data never gives an all-clear
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Each verdict is the worst of its signals, and the Why card shows every one of them. A reading over a week old can keep a warning but can't give Low Risk.
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Camera scan
A screening aid, not a diagnosis
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A model trained on photos of blooms, plants, clear water and shorelines looks at what your camera sees. It says Uncertain when it isn't sure, and a bloom you confirm near one of Jordan Lake's areas raises that area's verdict, on your phone only.
Worked out on your phone · Your exact location stays on it
About me
My name is Svar, and I'm a high school student at Green Level High School in Cary, North Carolina. I built JordanWatch because harmful algal blooms are an unfortunate reality in our local lakes. It's important to know when a lake is risky before you get in, so that people and pets can avoid harmful exposure.
JordanWatch combines public satellite data with U.S. Geological Survey stations to rate about 7,000 lakes across the United States. In doing so, data is collected and organized into a format easily readable by the public.
Data sources and credits
- Satellite: U.S. EPA CyAN, with NASA, NOAA and USGS
- Rain, rivers, lake level, stations: USGS Water Data
- Wind: Open-Meteo
- Tap water: EPA water system areas and records (SDWIS)
- Map and beaches: © OpenStreetMap contributors, ODbL
- ZIP locations: U.S. Census ZCTA Gazetteer
- State standards: EPA Criteria Search Tool, state rules
- After-contact steps: CDC, Harmful Algal Blooms and Your Health
- Report routes: state agencies and EPA
- Code: Leaflet, TensorFlow.js · Typeface: Public Sans
Camera training photos
- Algal Blooms Sweden (Zenodo, CC BY 4.0)
- iNaturalist
- Wikimedia Commons
- Open Images
- Florida DEP Algal Bloom Site Visits (Florida public records)
- USGS
- Credited photo by photo in the project's files
Not an official advisory
Estimates from public data, not lab tests. Follow posted signs.
Limits
- Satellites can't measure toxins
- They can't see narrow arms or the shoreline
- Readings can be days old
- Follow your state's advisories
- Stay out of water that looks green, scummy or like spilled paint