Algal bloom and satellite glossary.
Plain explanations of terms used in bloom response and satellite analysis.
Algal bloom
A rapid increase in phytoplankton, especially cyanobacteria, that turns water green. Common in still, warm water in summer.
Cyanobacteria
The main group of microorganisms behind harmful blooms. Some produce odour compounds or toxins.
Chlorophyll-a
The pigment in phytoplankton, used as an indicator of how much phytoplankton is in the water.
Algae alert scheme
A system that announces bloom levels for drinking water sources and recreational waters, based on cyanobacteria cell counts from field sampling.
NDCI
Normalised Difference Chlorophyll Index. It estimates chlorophyll from the difference between the red-edge and red bands of satellite images.
Red edge
The wavelength range between red and near-infrared light, where reflectance changes sharply with chlorophyll.
Sentinel-1
The radar (SAR) satellite mission of the European Copernicus programme. It observes through cloud and at night.
Sentinel-2
The optical satellite mission of the Copernicus programme, with 10 m resolution and red-edge bands.
SAR
Synthetic aperture radar: images made from returned radio signals. Calm water appears dark, so water and land can be separated.
GRD
Ground Range Detected, a Sentinel-1 product format projected to ground range.
Lee filter
A common filter for reducing speckle noise in radar images.
Residence time
How long water stays in a lake or river reach. The longer it stays, the easier it is for algae to build up.
Algae boom
A floating barrier that keeps algae away from an intake.
Intake depth adjustment
Changing the depth from which water is drawn to avoid the dense surface layer of a bloom.
TimesFM
A time-series foundation model released by Google. BASIN uses it with satellite time series and the five drivers.
p10 to p90
A forecast range: 10% of outcomes are expected below p10 and 10% above p90.
Recall
The share of actual exceedances that alerts correctly caught.
F1
A score that combines precision and recall. Higher when alerts catch more and miss less.
Work with us
Start with a satellite screening of your water.
We screen your reservoirs and intakes from public satellite data first, then compare the results with your own field measurements. No equipment needs to be installed.