The EyeOnWater concept consists of an App and a website. The app allows you as user to make a contribution to science and supply information about the water colour of fresh- as well as saline waters (lakes, rivers, coastal waters, seas and oceans) near your location or elsewhere. The measurement is sent to the central server, validated and stored, after which it is visible via the EyeOnWater.

Source: Android description / Image: pxhere

Useful information

Download: Android 4.1 (60MB) / iOS 9.0 (20.4MB) / web (visualization)

Price: free

Language: English

Runs offline: partially (connection required for sending data)

Last update: Android 04/12/2018 (v. 1.5.7) – iOS 11/12/2018 (v. 1.5.9)

Website of the developer: Maris


What colour is water? Maybe at school you learned that water is colourless, tasteless and odourless. But water really has color. In fact, this essential element for life can acquire different tonalities depending on the amount of algae or organic matter present, the rainfall registered, etc. Thus, colour has become a water quality parameter that provides valuable data to the scientific community.

EyeOnWater invites you to be part of that community of volunteers who collect data on the colour of fresh and salt water around the world. All you need to do is install the app on your mobile phone, take a photo, determine its colour and send it in for analysis and validation.

Information provided by the app

The operation of the application is based on the Forel-Ule color scale. This measurement system, used since the end of the 19th century, comprises 21 colour ranges from blue to green and yellow- browns. Its aim is to standardise the determination of water colour regardless of the observer’s perception.

The process for collecting the information, which can be seen in the attached video, is as follows:

  • Mobile device must be positioned horizontally in relation to the water surface.
  • Sun should be on your back, shining over your left or right shoulder. This gives the best conditions for the readings.
  • Take the photo and zoom in on it. You will see that the screen displays different color bands that you can slide from left to right and vice versa.
  • Select the color that you think is closest to the color of the photograph
  • Send the image

The use of the application is completely anonymous. However, in order to locate where the photos are taken, you must activate your location. If you are a regular user, you can create an account and link your device to the observations you do.

The app also has an option to save locally the registered information and send it when you have internet connection (Queued uploads), as well as a complete management tutorial (How to use the app) and access to all approved measurements located on a map (All measurements).

Image gallery

The screenshots correspond to the Android version of the application.

Images: screenshots 19/12/2018. © Maris B. V.


The video is recorded using the Android version of the application (3 min 48 sec).

More information


Technical Tracking Sheet of the quality of surface water during the course of the Barcelona World Race 2014/15 (Note: EyeOnWater replaces the Citclops app)

App measures color palette of lakes, seas, and oceans (Ocean News & Technologies, 25/04/2016)



The reserves of surface freshwater that we exploit for our development constitute only 1% of the total volume of water on the planet. The rest of this essential element for life is stored underground or in the polar caps, although the majority, 97%, is salt water. That is why their protection is vital and it is necessary to deploy all the useful strategies at our fingertips.

One of these mechanisms could be citizen science, an activity already discussed on this blog. Thanks to the thousands of volunteers around the world who contribute with their observations, the scientific community has more information to analyse and draw conclusions. And, obviously, the monitoring of river and marine resources is also an objective of these dynamics, as the present application demonstrates.

What kind of information does this app provide? Imagine, for example, that you upload an observation of a lake with greenish water. That colour of the water could be indicative of a process of eutrophication capable of endangering the development of the aquatic fauna of the place.

As strong points, to point out its simplicity of use and how well documented is its correct use. In addition, it has the guarantee that the images are validated before being uploaded to the map, which would allow to correct errors derived from an inadequate luminosity of the screen of the device, for example. Also, as an aspect to improve, perhaps it would be interesting to incorporate some information about the meaning of each color.

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Técnico de medio ambiente, community manager y content curator especializada en temas de medioambiente - Environmental technician, community manager and content curator specialised in environmental issues