Website provides real-time forecasts for Swiss lakes

Will the water be warm enough tomorrow to go for a lunchtime swim in Lake Geneva? Will you be sailing against the currents to Evian this weekend? What will be the best place to collect algae samples the day after tomorrow? The answers to all these questions can be found on a single website: www.meteolakes.ch. Initially developed three years ago by Theo Baracchini, a PhD student at EPFL’s Physics of Aquatic Systems Laboratory (APHYS), the project had a purely scientific goal: to enable scientists to view physical and biological data about Lake Geneva, collected over time and at different locations, that were previously difficult to obtain. But with around 330 visits a day last summer, the platform obviously became useful to more than just scientists – swimmers, sailors, beach authorities, boaters, fishermen, tourists, nature lovers and people who are simply interested in lakes. Baracchini therefore expanded his website as part of his thesis research, which he defended this Friday at EPFL.

“Meteolakes.ch is the first platform to compile lake data from three different sources: satellite images, in situ measurements and 3D computer simulations,” says Baracchini. While the first version displayed only water surface temperature and average current velocities, the website now contains a wealth of information including algae concentrations and water oxygen levels and lets users view data at different depths. Baracchini also enhanced the website’s models of Lake Geneva by adding temperature and water-velocity readings from the four main rivers that feed the lake: the Rhône, Dranse, Aubonne and Venoge.

An alert system

The updated platform contains new features as well, such as an early warning system that can predict major disturbances – like strong storm currents or upwellings – up to four-and-a-half days in advance and send an email to people who sign up for the service.

Here are two examples of disturbances the system could detect in 2018:

A localized storm hit Vevey on August 6.

In december, a gyre in the middle of the lake created an upwelling of cold water.

Another new feature is a “particle tracker” that can display particle dispersion patterns (such as for pollutant particles) associated with the currents modelled on the website. This feature was used to identify the origins of calcite precipitation (which caused the water to suddenly turn white) and could be useful in search and rescue operations.

As part of an open science approach – and to promote cross-disciplinary research on lakes – Baracchini made it possible for users to download the raw data generated by the website’s 3D models. Users can specify exactly what location, time period, variable and water depth they are interested in; the website will extract the data and send them electronically in formatted files.

A dynamic ecosystem

The final update was to incorporate real-time data feeds that operate in loops. When a satellite flies over Lake Geneva and records the water temperature, these data are incorporated into the website’s models, which are then used to plan on-site measurements, which in turn provide feedback on the satellite’s accuracy. Meteolakes therefore creates a system where each data source benefits the others. This new feature also enables the website to quantify and reduce uncertainty, making it one of the most sophisticated lake-data platforms in the world.

By providing a more detailed view of Switzerland’s lakes, the website makes it clear just how much is going on beneath their placid surface. “Each lake is a complex, vital ecosystem that is much more active and alive than we imagine. With Meteolakes, I wanted to not just help scientists study and predict the impacts of climate change or extreme weather events, but also to allow people who enjoy our country’s lakes to realize how dynamic they are,” says Baracchini