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22.03.2017 07:21 Age: 3 yrs

22 March, World Water Day: views from space

Category: Events

The use of satellite observation in hydrology is bound to be called on increasingly, with ever more uses combining all available measurements and data, for better management of this most vital of resources: fresh water.

Fresh water, essential for all life on Earth, is present in a finite amount on our planet (only 0.007% of all the planet's water is accessible for human consumption via rivers, streams, reservoirs and lakes).

In particular, it is essential for human activities. The consumption of fresh water is growing three times faster than the population. But global water resources are shared unequally between countries and continents: Asia accounts for 60% of the world’s population but has only 36% of its water, while South America has only 7% of the population but 30% of the water.

Today, water is no longer simply a problem for "poor countries": drought is increasingly afflicting areas of China, the USA, Australia and Europe. Aquifers are drying up and pollution and salinity are reducing water reserves even further. It has become essential to introduce tools to optimise the management of these resources.

At the moment, hydrology is essentially based on probes and gauging stations installed in situ at the edges of watercourses or lakes. But these instruments are distributed very unevenly across the surface of the globe, and it is often difficult to keep them properly maintained and calibrated. Satellite-based observation helps ensure the regularity and homogeneity of measurements from all over the planet. Satellite missions have led to major advances in environmental studies, including in the management of water resources. Among other achievements, nadir altimetry can acquire the height of the water of certain lakes or rivers, and the wide-swath altimetry made possible by SWOT will soon extend this possibility to include all inland waters.

Precipitation, evaporation and evapotranspiration, water levels and surface areas, the extent of frozen regions, soil moisture, groundwater reserves, water quality, surface water temperature, depth, mapping of watersheds – all this information can be and already is being provided today by Earth observation satellites. In addition, by combining all these sources, combining some of them with in situ measurements and/or with models, synoptic maps can be compiled on the situation of a watershed, a water deficit for example, risk maps, estimates of the flow of rivers, snowmelt, or the speed of the flow and shrinkage of glaciers.

The use of satellite observation in hydrology is bound to be called on increasingly, with ever more uses combining all available measurements and data, for better management of this most vital of resources: fresh water.


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