MONITORING OF WATER RESOURCES BY SPATIAL ALTIMETRY

Abstract

Although most of the space missions discussed here have not been primarily dedicated to hydrology, 31 years of spatial altimetry have provided complementary data that can be used to create hydrological products for watersheds, such as time series water levels, estimates of river flows, longitudinal riverbed altitude profiles, minimum and maximum elevations, or leveling of stations in situ. The raw data still suffer from uncertainties of several decimeters. Today, altimetry techniques are evolving rapidly. One direction is the change of the radar band, from Ku to Ka. Another change is the replacement of the current LR Mode with SAR or Interferometry modes. Both evolutions tend to drastically decrease the imaged range, reducing both the contamination of the echo by the environment of the water body, and improving the vertical accuracy. Finally, as of 2015, the research missions were replaced by operational ones, making the longevity of the sampling sites more certain. All the aforementioned technical evolutions have been grouped together in the SWOT mission, a Ka-band interferometric altimeter, the first satellite mission actually dedicated to providing full coverage of continental waters, launched in December 2022.