While yesterday, we celebrated Water Day, UNESCO and UN-Water warn of an imminent risk of a global water crisis. It therefore seemed interesting to us to introduce you in a little more detail to the Swot satellite, one of whose missions is to better understand the water cycle and its impact on the climate, by focusing on oceanography, hydrology and the coast, which has never been done. Explanations from Annick Sylvestre-Baron, Cnes manager of the Swot program, and Philippe Maisongrandre, Cnes manager of the Continental Surfaces program.
Launched in December 2022, aboard a SpaceX Falcon 9 launcher, the Swot satellite will revolutionize hydrology by carrying an altimeter at an altitude of 891 kilometers capable of monitoring the rivers and lakes of our Planet. Swot will thus be the first mission to take an almost exhaustive inventory of the water stocks on the Earth’s surface and to monitor their evolution, and therefore to improve understanding of the freshwater cycle and its impact on the climate. . While Unesco and UN-Water warn of an imminent risk of a global water crisis for some 3 billion Earthlings, this mission is much more necessary and interesting than it seems.
Annick Sylvestre-Baron, Cnes manager of the Swot program, explains to us all the interest of this mission which will revolutionize our knowledge of the water cycle on the planet “and why there will be” and before and following Swot “. By focusing on oceanography, continental and coastal hydrology, Swot aims to ” to improve our knowledge of the water cycle, a cycle intimately linked to the climate and its changes “. It is in fact ” the first altimetric imaging mission dedicated to observation of the level of fresh and salt water on the Planet » in order to monitor of almost exhaustively the stocks of’water in lakes, reservoirs, even in wetlands ».
Understanding the behavior of the continental hydrological cycle
Thus, Swot will complete the range of observations by accurately measuring new parameters essential to resource monitoring., such as “the heights, the slopes, making it possible to assess the flow of the main rivers, a fundamental piece of data which is currently lacking “says Annick Sylvestre-Baron. From its orbit, Swot will access all water surfaces, including hard-to-reach areas such as the many lakes in Canada or Siberia, which represent a significant part of the volume of fresh water on Earth, this or blue which will become more and more coveted.
To understand the great interest of Swot, Philippe Maisongrandre, Cnes manager of the Continental Surfaces program, reminds us that ” fresh water accessible in liquid state represents less than 1% of all water on the globe. It is therefore important to be able to estimate the availability of this water on the continents and its evolution in time and space “. However, the current altimetric observations “ it is not make it possible to cover all the continents in such a regular manner “. Swot will correct this bias.
Associated with other spatial data (optical, thermal, passive microwaves, gravimetric…), Swot data will allow us to “ better understand and know the water cycle on a global scale for the moment poorly known “. It should be known that, if the total quantity of water on Earth has been unchanged and constant for millions of years, “ la distribution between the oceans, continental surfaces and the atmosphere is constantly changing ».
Surprisingly, there is enough water on Earth
Absolutely, there is enough fresh water on Earth but there is a problem of juxtaposition between the needs of populations and the spatio-temporal distribution of the resource “. On the continents, certain regions are affected by the lack of rain, the massive drying up of the soil and the drop in the water tables. In other regions, the rainy episodes are intensifying because of the rise in temperatures which reinforces the precipitating power of the clouds, which causes increasingly frequent floods. For example, in early 2023, some French regions have just experienced several consecutive weeks without rain. ” The climate change accentuates these phenomena by increasing their frequency and intensity “. Swot will make it possible to better diagnose and better understand these changes in order to anticipate them and better manage them.
“There is enough fresh water on Earth but there is a problem of juxtaposition between the needs of populations and the spatio-temporal distribution of the resource ”
In a context of population growth and climate change, Swot is therefore timely. Its data will contribute facilitate water management decisions and will also provide new insights into its global cycle “. Indeed, the measurement of the flow of rivers and the prediction of the height of the waters have a strong application potential in many fields such as ” management of drinking water resources, crop irrigation, river navigation, prediction of floods and floods, or the production of hydroelectric and nuclear energy (thermo-regulated by river water) », wants to let us know Philippe Maisongrandre.
Resulting from major technological innovations, Swot data will therefore not only be of interest to the scientific community. Thanks to the Aval program, from which Swot benefited, the data from this satellite will be useful for many concrete applications in everyday life.
Good to know
If you want to know more regarding the Swot mission, we interviewed Sophie Coutin-Faye, head of the altimetry department at Cnes, and Nicolas Picot, Swot downstream project manager, who explain to us why this is a unprecedented, spectacular and scientifically revolutionary. We also interviewed Christophe Duplay, Swot program manager for Thales Alenia Space, who built the satellite.