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EPA app serves as image-based HAB warning system

July 21, 2021

The U.S. Environmental Protection Agency (EPA) has launched CyANWeb, a web-based early warning system against harmful algal blooms (HABs) for over 2,000 of the largest lakes or reservoirs in the nation.

Federal researchers have designed the app to help local partners identify algal bloom formations in water where people swim, fish, and boat.

Current and historical remote sensing images inform daily or weekly updates. Specific changes in water color trigger alerts to water quality managers, lake management organizations, and volunteer monitoring groups in order to help prevent and reduce cyanobacterial threats to surface water quality.

CyANWeb users can access the application from mobile devices such as a smart phone or tablet) as well as a desktop computer. They can view comparisons of multiple water bodies over time, as well as mark locations for future reference.

“Making this satellite data available across more platforms will improve our ability to respond to harmful algal blooms,” said Jennifer Orme-Zavaleta, Acting Assistant Administrator for EPA’s Office of Research and Development and the EPA Science Advisor. “The release of this update is another step towards ensuring the quality of our nation’s drinking and recreational waters.”

CyANWeb has been developed by the Cyanobacteria Assessment Network (CyAN) with input from users across the country. The CyAN partnership includes researchers with the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Geological Survey (USGS).

CyANWeb uses satellite data that was previously only available within the experimental CyAN Android mobile app EPA released in 2019. CyAN is available for download in the Google Play store for Android devices. EPA note: The CyAN app provides provisional satellite-derived measures of cyanobacteria, which may contain errors and should be considered a research-level tool. The primary satellite sensor collecting data is the European Space Agency’s Copernicus Sentinel-3 Ocean and Land Colour Instrument.

For more information on either of EPA’s CyAN or CyANWeb applications, visit