Photographing water

How do you photograph something that doesn’t stay still, or that is covered by other things, or that is too far away? Remote sensing and real-time monitoring technologies of water basins through sensors and algorithms promise to solve these problems at least in part. Here’s how they are used, between art and science

Rivers flow, the water level of lakes changes: freshwater reservoirs presuppose a movement that is difficult to capture in a single, static image.

For centuries we have been trying to describe and estimate how much water there is and will be in a given territory through field observations and increasingly refined processing and investigation tools. In the last twenty years, the development of Internet of Things¹ has made the structuring of real-time measurement and monitoring systems in various sectors possible. IoT has added to remote sensing systems such as radar or lidar.

The set of these technologies applied to water bodies is called the Internet of Water and is increasingly used to measure and manage water needs in different parts of the world.

The Global Water Futures Observatories in Canada

Last April, the enhancement of the Global Water Futures Observatories² was officially launched in Canada: this national freshwater scientific observation network now includes nine universities and manages 64 water observation sites in lakes, rivers, wetlands and mountainous areas , 15 specialized remote sensing systems and 18 water quality laboratories. Present since 2016, it has received new impetus from funding for the period 2023-2029 from the Canada Foundation for Innovation.

From drones flying over glaciers to smart buoys in lakes, everything is used to collect data useful for monitoring the health of fresh waters. These data are processed with the help of specific algorithms, programmed to identify any anomalies such as temperature variations, proliferation of algae or presence of dangerous bacteria, and to trigger alarms in good time.

Early warning is the key to starting to structure policies to mitigate climate change which is already underway and is causing water crises in Saskatchewan, the province where the university that coordinates the observatory is based.

All the observatory’s data are released in open access³ to contribute to the definition of water flow forecast models in relation to extreme events such as floods and droughts, to better design of irrigation and agricultural techniques, and therefore to better management of the national requirement.

The Internet of Water in Flanders

A similar project was implemented from 2019 to the end of 2023 in Flanders, the Flemish region of Belgium: a network of public and private bodies, including Aquafin, the public wastewater treatment company, and the government’s Flanders Environment Agency, has structured the Internet of Water Flanders⁴, a prototype for real-time digital monitoring of water quality indicators.

At specific points of rivers, canals, underground wells and waste water treatment plants, particular low-cost sensors programmed to measure the acidity, concentration of salts and temperature of the water were positioned: the objective was to counteract the salinisation of freshwater due to increasing droughts and low groundwater levels.

Also in this case, the monitoring of the various parameters on water quality has made it possible to develop more updated mapping, study the interactions between groundwater and surface water and estimate the impact of water needs for field irrigation or civil uses.

SWOT space mission maps

At least twice every 21 days, the SWOT satellite sends information about large rivers, lakes and reservoirs back to Earth: this information is used to create global, high-definition maps. SWOT – Surface Water and Ocean Topography is in fact the first satellite mission with the aim of producing the first complete survey of fresh water on Earth, that is, of providing data on over 95% of lakes larger than 62,500 square meters and on rivers more than 100 meters wide.

Created by NASA and the French Center National d’Etudes Spatiales in collaboration with the Canadian and British space agencies, the SWOT satellite was launched on December 15, 2022 and is still in orbit.

Thanks to an integrated technological system⁵, it is able to measure fresh and salt water levels to an accuracy of approximately one centimeter. The basic technology is radar, i.e. the detection of the position and speed of an object through the measurement of electromagnetic waves at a specific frequency, radio waves. A radar antenna emits radio waves at intervals and captures the “rebound” signal of the same wave against the target object.

Among the different radar systems, SWOT uses a microwave one, which penetrates the clouds, reaches the earth’s surface and collects the “rebound” signal in any atmospheric condition, both day and night. Two radar antennas of this type are positioned on the SWOT satellite, which collect data simultaneously: from the “bounce” of the radio signal on the earth’s surface, high-definition images can be processed that identify and describe the position and flow rate of water basins. The variations in altitude of the earth’s surface based on wavelength are identified thanks to interferometry, the measurement of interference between radio waves. The result is images, called interferograms, in which these variations are defined by color.

In a study published last April in Nature Geoscience⁶, the mission’s researchers provided new estimates on the flow rate of terrestrial rivers, the speed of ocean outflow and the fluctuation of these data over time, with useful indications on the areas marked by a intensive water use, including  the Colorado River Basin in the United States, the Amazon Basin in South America, which contains about 38% of the world’s river water, and the Orange River Basin in southern Africa.

The areas were identified starting from the observations of the satellite, and in particular from the high definition global map.

Daniel Coe’s images from Lidar data

LIDAR-Light Detection and Range technology is similar to radar technology, but uses pulsed laser light instead of radio waves. A Lidar system is composed of a laser that emits the signal, a sensor that collects the “rebound” signal and software that processes the data and returns the “point cloud” from which three-dimensional maps can be further processed.

Lidar systems are widely used in geology to measure and describe morphological changes: almost 12 years ago the cartographer Daniel Coe began using them while working for the Department of Geology of the Oregon government, in the north-west of the United States. «From a way to learn to use new software it has become an artistic project through which I explore the changes in waterways over time» he says.

Daniel Coe is a cartographer. He lives in Olympia (Washington, USA). He holds a Bachelor of Arts from Portland State University and has worked for years for government bodies providing public information on local geology, first the Oregon Department of Geology and Mineral Industries (2010-2015), then, since 2016, the Washington Geological Survey. Specialized in the use of LIDAR data, in parallel he artistically processes scientific images from public databases for dissemination purposes.

Find out all his images

His images of bodies of water have been used as popular illustrations, book covers, music albums, magazines and film festival posters. «I like to find different places in the world with interesting rivers» he explains. «I live in the state of Washington, in the north-west of the United States, on the border with Canada, an area that about 15,000 years ago was covered by a large ice cap: with in the Lidar data you can see the channels where the rivers flowed around the glacier, it’s a kind of time machine. Or you can see how dams, embankments and human infrastructures have changed the path of the rivers, straightening them or how, vice versa, the borders of the rivers that marked two States have changed».

Coe’s images derive from open source data provided by government sources: «In these portals you can download small sections which then need to be stitched together to form a large area, which is usually called a digital elevation model or a digital terrain model and corresponds to a smooth surface model of the Earth” he explains. «Once the data is downloaded, I use a GIS system to process it and change the colors through a scale of gradients and then I use further graphics software to refine it». The process can last from a few hours to a few days: «If you start from the point cloud collected by the LIDAR system, more processing is required, but if the starting point is the digital elevation model, less time is needed».

Even the images processed from LIDAR data can serve to represent the human impact on rivers: «I have some images of the Colorado River delta, of the tidal channels where fresh water meets salt water that look like dead trees. It seems to me to be an excellent metaphor for the drying up of the river due to hyperconsumption» underlines Coe. «Lidar and elevation data are a great way to show how waterways have changed over time due to global warming. I think making something aesthetically beautiful is the first step in getting people to think about these topics».

In his opinion, LIDAR technology, which does not allow us to see through the water except to a minimal extent, is not suitable for portraying the variation in the water level of lakes but is very well suited for the description of rivers: «Thanks to the lidar it is possible to digitally remove the vegetation and directly see the bare earth, the surrounding terrain, and therefore the signs of episodes that occurred a long time ago» explains Coe. «I personally learned that rivers are truly living beings in many ways: even in places where humans try to dam them or prevent their movement, they will eventually move and resume their course». But with what consequences for us human beings?

1. The Internet of Things is the process of incorporating the Internet into objects and environments, through embedded processors or IT architectures (edge, fog, cloud computing) which involve a combination of sensors and big data processing software. ↩︎
2. https://gwfo.ca/index.php ↩︎
3. Global Water Futures Observatories. Access or request data. https://gwfo.ca/data/access-request-data.php#GWFNetDataCatalogue. ↩︎
4. Real-time data for better water management. Internet of Water Flanders. https://www.internetofwater.be/en/. ↩︎
5. NASA SWOT. Flight Systems | Mission. https://swot.jpl.nasa.gov/mission/flight-systems/. ↩︎
6. Collins, E.L., David, C.H., Riggs, R. et al. Global patterns in river water storage dependent on residence time. In Nat. Geosci. 17, 433–439 (2024). https://doi.org/10.1038/s41561-024-01421-5. ↩︎