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## Action
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## Hotspot
### Tooltip
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## Media
### Title
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### Video
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### Video Subtitles
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## Popup
### Body
htmlText_A2C36340_B5D8_65A0_41E1_7928C61F03E9.html = Damien Bouffard, Member of the Léxplore Steering Committee, Eawag
Acoustic Doppler Current profiler
Anchor line for different sensors
Automated water sampling system
Temperature measuring chains
Weather station and CO₂ sensor
A certain combination of sensors is required depending on the aim of the research. To facilitate a more flexible set-up, there is an anchor line on the LéXPLORE platform that can be used to mount sensors as required. For example, sensors for measuring the water temperature, oxygen content and photosynthetically active radiation were installed from October 2018 to March 2021 as part of a project to determine primary production. Since March 2021, the line has been used in another research project.
Projects
Data
A moon pool is an opening in the bottom of a boat used for gaining direct and safe access to the water below the deck. LéXPLORE has two square moon pools, each measuring 1.5 by 1.5 metres. One is outside on the platform and the other is inside the cabin. Researchers use the moon pools to collect water samples and take various profile measurements using an electric winch. Instruments that are not completely weather-resistant can be used in the moon pool inside.
A safety perimeter of 70 metres surrounds LéXPLORE to ensure that passing boats and fishing nets do not interfere with the measuring instruments floating in the water. The no-go zone is clearly delineated by 39 yellow buoys, 9 of which are illuminated. Measurements can be taken without any disturbances in an area of 15,000 m² around the platform.
A weather station is installed on the mast of the cabin’s external wall, 5 metres above the surface of the water. It contains a rainfall gauge, a wind sensor to measure the speed and direction of the wind, a probe to measure the air temperature and humidity, a pyranometer to measure the global solar radiation and a barometer to measure the air pressure. A CO₂ sensor is installed directly adjacent to the weather station – this continuously measures the concentration of carbon dioxide in the air at 2.5 metres above the surface of the water.
Data
Alors que la température de l’eau peut se mesurer directement avec des thermomètres, celle de la surface de l’eau ne peut être déterminée qu’indirectement. C’est le rôle du radiomètre qui mesure le rayonnement infra-rouge émis par la surface de l’eau. Des satellites enregistrent aussi les températures en surface selon le même principe. Les données du radiomètre à infrarouge aident à calibrer les données satellite afin de permettre la com-paraison des températures mesurées directement dans le lac et à quelques centimètres sous la surface de l’eau.
Données
Als Moonpool bezeichnet man eine Öffnung im Schiffsrumpf, durch die man vom Deck aus direkten und sicheren Zugang zum Wasser hat. LéXPLORE verfügt über zwei solcher Moonpools, die je 1,5 × 1,5 Meter gross sind, einen im Aussenbereich der Plattform und einen im Innern der Kabine. Die Moonpools dienen dazu, Wasserproben zu entnehmen und mithilfe einer elektrischen Seilwinde verschiedene Profilmessungen zu machen. Im inneren Moonpool können auch Instrumente eingesetzt werden, die nicht komplett wetterbeständig sind.
An electric cable winch is installed at the edge of the moon pool outside. This allows different biogeochemical and physical parameters to be recorded every 10 centimetres when profiling. These cable winches are used to lower water sample containers or measuring sensors on vertical profilers into the lake at a specific and constant speed.
Cytobuoy is what is known as a flow cytometer, an instrument for measuring particles in a fluid. The Cytobuoy records the concentrations and composition of plankton in the water at a predefined depth in the moon pool inside the cabin.
Deux sonars split-beam émettent des impulsions sonores dans l’eau à une fréquence comprise entre 70 et 200 kilohertz afin de localiser les poissons dans la colonne d’eau sous la plateforme. Les données des sonars indiquent où se trouvent les poissons, comment ils se déplacent dans la colonne d’eau et comment leur présence se modifie en fonction de la température et de la lumière. Ils permettent même de détecter les larves de poissons. Les données des sonars sont également importantes pour d’autres propriétés de l’eau influencées de manière déterminante par la présence de poissons, comme par exemple les taux d’ammoniaque et la concentration de zooplancton.
Ein Grossteil der Daten, welche die verschiedenen Messinstrumente auf LéXPLORE erfassen, werden in Echtzeit auf die Online-Datenplattform Datalakes hochgeladen und sind öffentlich zugänglich. Die Diagramm-Ansicht zeigt eindrücklich, wie sich etwa die vertikalen Temperaturprofile, der Sauerstoffgehalt des Wassers, die Wellenhöhe und eine Vielzahl weiterer Parameter über die Zeit verändern.
Daten
LéXPLORE is a floating research laboratory on Lake Geneva. Up to 16 people can use the 10-by-10-metre platform with cabin at any given time. It was built in 2019 and is equipped with a range of state-of-the-art high-tech measuring instruments. Researchers from all over the world can use it to investigate various parameters and processes in the lake at any time of day, no matter the weather. What is the oxygen content level in the water? Are there any changes in vertical mixing? What about fish stocks? And what is the proportion of microplastics in the lake? These are just a few of the questions being addressed in the various research projects. The measurements provide information about the water quality and the condition of the aquatic ecosystem and important insights into the impact of climate change and land use on lakes.
LéXPLORE is a joint project of Eawag, EPFL, the Universities of Geneva and Lausanne and the French research center CARRTEL INRAE.
This virtual tour was produced by Eawag and EPFL.
LéXPLORE is fitted with two Acoustic Doppler current profilers, which are attached to a line 8 metres below the platform. One measures the current in the upper 8 metres, i.e. the surface layer, and the other faces downwards to record the current to a depth of 90 metres. The data is transmitted via cable to the cabin, where the current can be observed in real time.
Data
LéXPLORE produces its own electricity. The 28 solar panels fitted onto the roof, south-facing external wall and railing have been able to cover about 97 percent of the electricity required to date.
A diesel generator bridges the gap in supply during winter when there hasn’t been any sun for several days at a time.
LéXPLORE produit sa propre électricité. Les 28 panneaux solaires fixés sur le toit ainsi que sur le mur et la rampe extérieurs orientés au sud produisent aujourd'hui jusqu’à 97 pour cent de l’électricité nécessaire. Lorsqu’en hiver le soleil ne brille pas pendant plusieurs jours, un générateur au diesel peut prendre le relai pour pallier le manque d’électricité.
LéXPLORE produziert seinen Strom selbst. Die 28 Solarpanels,
die auf dem Dach sowie an der nach Süden ausgerichteten Aussenwand und Reling angebracht sind, konnten bisher rund 97 Prozent des Strombedarfs decken. Wenn die Sonne im Winter über mehrere Tage nicht scheint, können Stromlücken mit einem Dieselgenerator überbrückt werden.
On désigne par moonpool une ouverture dans la coque du bateau à travers laquelle on a un accès direct et sécurisé à l’eau depuis le pont. LéXPLORE dispose de deux de ces moonpools, dont les dimensions sont de 1,5 × 1,5 mètre chacun, l’un à l’extérieur de la plateforme et l’autre à l’intérieur de la cabine. Les moonpools servent à prélever des échantillons d’eau et à réaliser diverses mesures de profils à l’aide d’un treuil électrique. Il est possible d’utiliser des instruments ne résistant pas complètement aux intempéries dans le moonpool intérieur.
Samples of sediment particles floating in the water have been taken every month since 2019. Researchers lower sediment traps – Plexiglass tubes measuring 1 metre in length and 9.2 centimetres in diameter – to depths of 10, 30, 50 and 100 metres. They then weigh and analyse the sediment samples to determine the content of organic and inorganic carbon, phosphorus, nitrogen and metals. Microplastics can also be detected.
Projects
The Idronaut profiling system is installed in the moon pool inside the cabin and every three hours it records a vertical profile down to a depth of 60 metres. Some of the variables it measures are the temperature, conductivity, pressure, oxygen content, pH, turbidity, chlorophyll, phycocyanin – a pigment from the photosynthesis of cyanobacteria – and the photosynthetically active radiation.
Projects
Data
The LéWalk profiling system consists of a turbulence fine temperature sensor mounted on a measuring platform. The platform is attached to a drifting buoy and propelled by the surface waves, moving along a wire to a predefined depth before returning to the surface. As it moves through the water column, the sensor continuously records the turbulence. LéWalk can be used in any weather and provides multiple turbulence profiles every day.
Projects
The Thetis profiler is an autonomous measurement instrument with a series of modular sensors anchored at the outer perimeter of the safety zone. It rises and falls automatically in the water column between a depth of 0.5 and 50 metres, where the sensors measure various biological and optical properties. The vertical profiles recorded show, for example, how the conductivity, oxygen content, pH, fluorescence, irradiance and backscattering or photosynthetically active radiation change at different depths. These measurements are used, among other things, to calibrate satellite data.
Projects
The automated system takes water samples from a fixed depth at predefined intervals and stores them in a unit comparable to that of a refrigerator, at a constant temperature of 3 degrees. This makes it possible to store samples and then analyse them at a later date, such as for the nutrient content of the water.
The majority of the data collected by various measuring instruments fitted to LéXPLORE is uploaded to the online Datalakes platform in real time and is publicly accessible. The diagram view clearly shows how the vertical temperature profile, the oxygen content of the water, the height of the waves and many other parameters change over time.
Data
The wave buoy is positioned in the safety zone at a slight distance from the platform. It has been recording the height and length of the surface waves every hour since April 2022. Researchers can use this data, for example, to gain a better understanding of the CO₂ exchange between water and air. The wave data, which can be viewed in real time on the Datalakes data platform, is also of interest to the general public and, in particular, sailors.
Data
To investigate the lake water for microplastics, one cubic metre of water at a depth of 2 and 30 metres is pumped through a water filter system every 12 hours. Particles of plastic of different sizes become lodged in two filters – one filter mesh is 500 microns and the other 150. The particles are then analysed under a microscope in the laboratory to determine both the total quantity and the different types of plastic.
Projects
Two so-called split-beam echo sounders (sonar) emit sound pulses in the water at a frequency of 70 and 200 kilohertz to locate the fish in the water column below the platform. The echo sounder data provides information about where the fish are, how they move in the water column and how their volume changes depending on the temperature and light. The sonar can even detect fish larvae. The echo sounder data is also important for measuring other water properties significantly affected by the occurrence of fish, such as ammonia levels and the concentration of zooplankton.
Two temperature measuring chains, each fitted with 24 sensors, record the water temperature at different depths every 10 seconds. One chain measures the temperature from 0.25 to 18 metres below the water surface, and the second chain from 21 to 90 metres. The high temporal resolution of these temperature profiles allows researchers to observe even short-term changes, like those caused by a storm.
Data
Une majeure partie des données enregistrées par les divers instruments de mesure sur LéXPLORE sont téléchargées et mises à disposition du public en temps réel sur la plateforme de données en ligne Datalakes. Le diagramme montre de manière impressionnante comment les profils verticaux de température, la teneur en oxygène de l’eau, la hauteur des vagues et une multitude d’autres paramètres se modifient au fil du temps.
Données
While the temperature in the water can be measured directly using a thermometer, the water surface temperature can only be determined indirectly. This is done using a radiometer, which measures the infra-red radiation emitted from the water surface. Satellites use the same principle to record surface temperatures. The data from the infra-red radiometer help to calibrate the satellite data in order to compare them with the temperatures measured directly in the lake just a few centimetres below the water surface.
Data
Während sich die Temperatur im Wasser mit Thermometern direkt messen lässt, kann die Temperatur der Wasseroberfläche nur indirekt bestimmt werden. Diese Aufgabe übernimmt das Radiometer, das die Infrarotstrahlung misst, die von der Wasseroberfläche ausgestrahlt wird. Nach dem gleichen Prinzip erfassen auch Satelliten Oberflächentemperaturen. Die Daten des Infrarot-Radiometers helfen dabei, die Satellitendaten zu kalibrieren, damit sie mit den direkt im See, wenige Zentimeter unter der Wasseroberfläche gemessenen Temperaturen verglichen werden können.
Daten
Zwei sogenannte Split-Beam-Echolote senden mit einer Frequenz von 70 und 200 Kilohertz Schallimpulse ins Wasser, um in der Wassersäule unterhalb der Plattform Fische zu orten. Die Echolot-Daten geben Auskunft darüber, wo sich Fische aufhalten, wie sie sich in der Wassersäule bewegen und wie sich ihr Aufkommen in Abhängigkeit von Temperatur und Licht verändert. Selbst Fischlarven lassen sich damit erkennen. Die Echolot-Daten sind auch für die Messung anderer Wassereigenschaften wichtig, die massgeblich durch das Vorkommen von Fischen beeinflusst werden, zum Beispiel Ammoniakwerte oder die Konzentration von Zooplankton.