The water quality measurement network of the Institute for Hygiene and Environment operates measuring stations on Hamburg's rivers. The “Hamburg Water Data” app provides information about the water quality of the rivers. The data from the 9 measuring stations on the Elbe, Bille and the Alster area are updated hourly. Each measuring station can be accessed individually and provides information on the biological measured variables chlorophyll concentration and algae groups, as well as chemical-physical measured variables such as temperature and oxygen content. The current data and curves for the day, the month and the last year (currently - 365 days) are offered. The location of the measuring stations is displayed on a map. Favorites can be saved for regular use. The current version of the app has also been optimized in other areas and in terms of performance.