State-of-the-art potential of the GRACE satellite mission for solving modern hydrological problems

The paper presents the main results of using the GRACE mission in fields of study such as estimations of the components of basin water storage and water balance, and hydrological modeling. The estimate of error of GRACE data is in the order of 11 mm for watersheds with an area of 100 000 km2 and decreases with an increase of basin area. This accuracy made it possible to identify long-term and seasonal variability of water storage. It was shown that the decrease in total water storage in the Don basin for 2002-2019 is approximately equally caused by both soil moisture and groundwater changes. At the same time, the minimum level of groundwater was already reached in 2010; the minimum level of soil moisture - in 2015. Since 2016, Don basin groundwater changes very little during the winter period, which is likely due to the increased number of thaws and thinning of the freezing layer during this period. Based on the precipitation data from meteorological stations for the cold period of European Russia, the value of their systematic error was estimated at about 20-25 %. The comparison of the values of total water storage for the river basins of the northern part of European Russia, according to GRACE data and ECOMAG runoff modeling results, has shown their good coincidence (NSE = 0.78 ÷ 0.89). In comparison with GRACE, ECOMAG shows a smaller increase in water storage during the winter and a faster decline during the spring flood period. Currently, progress in the use of GRACE in hydrology is limited by the low spatial-temporal resolution of data, which, within the framework of the GRACE mission itself, will not be improved in the coming years. At the same time, the principle of GRACE operation can be applied in the future to various satellite constellations.