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Space hydrology

by LEGOS last modified May 03, 2015 05:44 PM

Water level time series on lakes, major rivers and flooded plains are provided by the Topex/Poseidon, Jason-1, ERS-1, ERS-2, Envisat and GFO space altimetry missions.


Terrestrial waters only account for 0.65% of all the Earth's water against 97% stored in the oceans and 2.15% in the cryosphere. Yet continental waters are crucial for life on Earth as well as human activities and domestic needs. They also have a strong influence on climate variability. Precipitation, evaporation and runoff into the sea continually recycle water on land. Better climate forecasting and management of the planet's water resources (consumption and human activities such as farming, urbanisation and hydroelectric energy production, etc.) call for increasingly accurate description of land surface water cycles.

The application of remote sensing techniques for measuring water mass variations in major river basins at time scales ranging from a few months to several decades has only recently been made possible.

The most promising of these techniques are satellite altimetry to measure the water level of rivers, lakes and flooded plains, and space gravimetry (GRACE mission, which provides spatio-temporal change in land water storage). In recent years, several studies have demonstrated the interest of satellite altimetry to study surface waters (rivers, lakes and flooded plains) thereby offering continuous, quasi-global monitoring of water levels. A new space mission (GRACE) lauched in 2002, measures spatio-temporal variations of the gravity field with a ground resolution (3°x3°) on time scales ranging from one month to several years.

One of GRACE's main applications is to quantify spatio-temporal variations of continental water storage (soil water, underground water and snow mass), for which there is no earth-based global scale observation to date. Only global hydrological models developed by hydrologists and climatologists provide information on these parameters.


Used in synergy with in situ measurements and model outputs, remote sensing observations will be of great value on the following issues:

  • Study of the global and continental water cycle, and its link with climate variability, anthropogenic disturbances and water resources

  • Specific hydrological problems of major river basin

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