ИСТИНА

In 2002–2019, GRACE mission data have been widely used in hydrology. They enabled calibration and validation of hydrological models, including data assimilation in them, monitoring of groundwater and soil water reserves, snow water reserves and, in some cases, even river water reserves and river sediment runoff. The independence of the results of measurements of the GRACE mission from the properties of the underlying surface gives it a unique advantage compared to classical remote sensing systems using electromagnetic radiation of objects. The contribution of GRACE data to the study of the flow of the rivers of the Arctic Ocean is significant. It is shown that the increase in the flow of Arctic rivers in the 21st century is not associated with permafrost thawing, and the existing network of ground-based precipitation observations underestimates the amount of solid precipitation by 20-25%. The GRACE mission is the only source of information on the groundwater variability at the regional and global level. The low rate of change in underground water reserves and significant long-term variability of these reserves, in comparison with surface waters, enable using GRACE data not only to monitor, but also to forecast underground water reserves. However, the practical application of GRACE data is very limited. The low resolution does not allow to use GRACE data for the study of small and medium river catchments. Floods associated with heavy rainfalls or large amounts of water in the snow, even on large rivers, form within a few weeks, and data available in two-month delay are useless for forecasting. Currently, the practical use of satellite gravimetry data in hydrology is possible only within the framework of a system that assimilates both altarnative remote sensing data and model solutions. One example of such a system is the EGSIEM Hydrological Service.