bateau lac de guerlédan
© Simon Rohou

Experiments at Lake Guerlédan: climate and educational considerations

Hydrography - Oceanography
In the middle of October, ENSTA Bretagne’s hydrography and robotics engineering students met on the banks of Lake Guerlédan for the traditional "field camp": one week spent deploying measuring instruments, retrieving data, testing out robots and new systems, finding solutions to any problems encountered and raising the upcoming generation’s awareness of science.
lac de guerlédan niveau
© Simon Rohou

Climate: measuring the impact that drought has had on the lake

For this new season at Guerlédan, the hydrography and oceanography professors found that the level of the lake was 5 meters lower than the level usually measured in October. Drought-related, this drop in level has more than one cause: it stems both from the evaporation of water and from ramped-up supplies to the nearby drinking water station.
A group of hydrography and oceanography students have been set a research topic to understand the impact of the 2022 summer drought on the lake.

The students will be able to use all the previous data collected since 2016 and compare this to the new data acquired this year to identify the potential impact climate change is having on the lake. Chlorophyll, in particular, is a good marker of primary production and therefore, by extrapolation, of life in the lake, explains Amandine Nicolle, hydrography and oceanography professor.

The students now have several weeks to compare these datasets and shed light on the impact of this drought: has it impoverished the lake?
The students’ findings will be unveiled when the projects are formally presented in February.

guerlédan cage
© Simon Rohou

Robotics: securing exploration of the underwater environment

All week long, the students majoring in mobile robotics tested out different robots and associated devices. This included the “niche” (photo opposite). 

When exploring an underwater environment, tools need to be developed for retrieving the robots securely. This particularly makes it possible to charge their batteries and save the data acquired. A cage system has been designed to fulfil this mission. Because the water is opaque, the robot (ROV: remotely operated underwater vehicle) uses an acoustic system to navigate towards the cage initially, before being able to visually identify the cage with its camera, explains Simon Rohou, robotics professor.

It was possible to test the whole system successfully in Lake Guerlédan.

© Simon Rohou

A shared passion for science 

With a view to sharing knowledge and educating in science, the ENSTA Bretagne students welcomed the schoolchildren at St Aignan primary school for a day given over to finding out about robotics and hydrography in a fun and straightforward way. 

  • Bathymetry: measuring water depth using the lead-line method
  • Robotics: guiding a boat along the water remotely
  • Sound: recognizing different sounds emitted and matching them to images (e.g.: whales, gulls, ship, etc.)
  • Water characteristics: demonstrating the differences in density between hot water/cold water, saltwater/freshwater, using dyes

The schoolchildren were all rewarded with a "Treasure" at the end and went away with a smile and their “hydrography explorer” certificate specially issued for the occasion.

We were very pleasantly surprised to see how enthusiastic and attentive the pupils were during the workshops. Léna, 2nd year engineering student, Hydrography major.