Citizen observations of water quality

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Deltares | R&D Highlights 2015 Ecosystems and Environmental Quality

Citizen observations

of water quality

Observations made by the general public provide useful information about our environment. The resulting data are used, for example, in meteorology to learn more about spatial variations in a country. Estimates of bird populations and phenology also rely heavily on observations by volunteers. Since the introduction of smartphones, many citizens have a camera and an internet connection. This provides new opportunities for the easy collection of citizen data. The EU FP7 project CITCLOPS has led to the development of various smartphone-based citizen observation concepts for the determination of optical water quality.

Water colour is a useful source of information about water quality. The combined concentrations of phytoplankton, suspended matter and dissolved organic matter determine the water colour and transparency. The relation between water colour and coloured substances in water is commonly used in satellite remote sensing, which involves the use of sophisticated sensors. Alternatively, relatively simple smartphone cameras and even the naked eye can be used to retrieve quantitative information about water colour. At the turn of the nineteenth century, Forel and Ule developed a colour scale (the FU scale) to determine the colour of open water (from deep blue via green to brownish). Since then, a vast number of colour observations for lakes and oceans worldwide have been made using the FU scale, and they can be used to determine long-term trends and patterns.

The FU scale has been included in a smartphone app in the CITCLOPS project. This app - Eye-On-Water - allows observers to take a picture of the water and compare the colour with the FU colour scale on the screen. The app uploads the picture, the FU observation and additional information about weather and water transparency to a database. The app also contains image-processing algorithms to validate the FU values reported by the

user. The data in the database can be viewed and downloaded from the website www.eyeonwater.org. The Eye-On-Water app is available for both iPhone and Android smartphones.

The Deltares CITCLOPS team analysed how observations collected by the public with the Eye-On-Water app can be used to map variations in water quality and monitor long-term changes in the concentrations of phytoplankton, suspended matter and dissolved organic matter. One of the key questions for Deltares is how observations of this kind can contribute to monitoring and decision-making by water managers such as water authorities and Rijkswaterstaat. A typical benefit of citizen data about water colour is that they make it possible to remedy spatio-temporal gaps in standardised water-quality monitoring networks. Most traditional monitoring schemes focus on larger-scale characteristics and therefore tend to miss extreme events and local hot spots. Since the general public is usually inclined to report observations in areas where they are personally concerned about their environment, sharing their findings with local authorities in an app also provides an excellent means of communication and stakeholder involvement.

Further work in CITCLOPS has shown that the smartphone-based observations are valuable as a way of complementing ocean colour satellite imagery, in particular in nearshore and shallow waters, such as beaches and bays, fish farms and so on where satellite observations are less reliable. The CITCLOPS partners therefore developed an FU algorithm for multispectral satellite data that allows them to be compared with smartphone-based observations on the ground.

Screen view of the www.Eye-on-Water.org data viewer

QR code for downloading the Eye-on-Water app

Left: The Eye-on-Water app combines both visual and camera observations of Forel Ule colours. (Photo M. Wernand NIOZ). Right: Classical Forel-Ule scale.(Photo NIOZ)