What does water colour indicate?

One of the most apparent characteristics of water to the human eye is water colour. Water colour indicates the algae and organic content of the water that feeds organisms. Your observations are therefore valuable to scientists and water authorities.You can now contribute by downloading our EyeonWater app!

eyeonwater app

16-08-2021 - Important for Android users: Our previous app has been removed. We have released a new version here. We are sorry for the inconvenience.

Our observations


The EyeOnWater colour app helps us to classify rivers, lakes, coastal waters, seas and oceans on it's colour (it can be used for both fresh and saline natural waters). The observations via the app are an extension of a long term (over 100 years) set of water colour observations made by scientists in the past. You can view them all together in this map application.

View the map of colour observations


Clarity observations are usually done by Secchi Disk, lowering a white disk in the water and measuring to what depth it is still visible. EyeOnWater has collected a large dataset of observations from the past, and this set has been extended by citizens and volunteer measurements contributed via the EyeOnWater app.

View the map of clarity observations