The disadvantage of the measurement method, as the researchers point out, is that the spatial resolution of the gravitational field data is relatively poor and is only about 300 by 300 kilometers. Therefore reliable data can only be made in areas of about 100,000 square kilometres, which roughly corresponds to the area of the East German federal states. In addition, some other annoying effects must be eliminated. The Earth’s gravitational field also changes without sharp fluctuations in water masses, for example because in some areas the Earth’s crust is still rising after the disappearance of glaciers in the Ice Age.
Over large parts of the observation period, particularly in the years between 2004 and 2015, results from all four assessment methods agree well. The main differences were at the beginning and end of the time series. So slightly different analysis periods lead to significantly different trend values. So the GFZ hydrologist and lead author of the study, Andreas Güntner, points out: “Observations from all datasets show that a year with higher precipitation like 2021 is not enough to compensate for the lack of water storage that has accumulated over a longer period of time, to bring the balance back.” The series of observations urgently needs to be continued in order to be able to record and predict the long-term behavior of storage and water supply dynamics in Germany.
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