life · what lives on it
Lake algae
Is this lake growing a toxic algal bloom? Sentinel-2 reads the red-edge colour cyanobacteria give water, on every lake on Earth every few days.
What it shows
Is this lake growing a toxic algal bloom? Sentinel-2 reads the red-edge colour cyanobacteria give water, on every lake on Earth every few days. Sixteen lakes with documented recurring blooms, from Lake Erie and Taihu to Lake Victoria, Dianchi and Billings, are read live and ranked by estimated chlorophyll-a; search or pick any other place and the water within about 5 km of it is read on the spot. NOAA's free CyAN covers only US lakes.
Where the data comes from
Copernicus Sentinel-2 L2A through the Sentinel Hub Statistical API (Copernicus Data Space Ecosystem), last complete 30-day least-cloud composite; NDCI after Mishra & Mishra 2012; chlorophyll regression Kravitz et al. 2021; WHO recreational-water Alert Level Framework.
Reading the map
Colour is the WHO recreational-water band of the estimated chlorophyll-a: green low, amber moderate, red high, magenta very high. The dashed box is exactly the water Sentinel-2 was asked about.
Units NDCI = (B05 - B04) / (B05 + B04) over water pixels (NDWI > 0); chlorophyll-a µg/L = 826.57 NDCI³ - 176.43 NDCI² + 19 NDCI + 4.071; WHO bands: low < 10, moderate 10-50, high 50-5000, very high > 5000 µg/L.
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