Low Water Stage Marks on Hunger Stones: Verification for the Elbe River in 1616–2015
Authors: Elleder Libor , Kašpárek Ladislav , Šírová Jolana , Kabelka Tomas 
Published: November 2019

Abstract. The paper deals with the issue of documenting hydrological drought with the help of drought marks (DMs) which have been preserved on dozens of hunger stones in the river channel of the Elbe in Bohemia and Saxony. So far, the hunger stones have been regarded rather as an illustration of dry seasons. Our aim was, among other issues, to draw attention to the much greater documentary value of hunger stones and individual dry year marks inscribed on them. Therefore, we wanted to verify their reliability and better understand the motivation of their authors. For this purpose, we used the current extreme drought period of 2014-2019 which allowed detailed documentation of hunger stone in Děčín with marks from 1536 to 2003. Thanks to the helpful position of the object near the water gauge, we could compare the measured mark heights with the corresponding water levels. Simultaneously, we have scanned the object into 3D format so that it is possible to perform a detailed inspection of all marks, even those that were overlooked during field survey. A review of scientific and technical literature from the 19th century showed that marks of low water levels on stones and rock outcrops were to some extent interconnected with other important points. They were linked to zero points of water gauges, initially set up for navigation purposes, and also to flood marks. A particular situation in Děčín is therefore a unique example of epigraphic indication of low and high water levels in the enclosing profile of the upper part of the Elbe river basin. To verify the marks of low water levels we used the then current scientific studies which in the past brought the identification of dry periods. However, we also used the oldest series of daily water levels measured in Magdeburg, Dresden, and Prague, available by 1851, i.e. by the beginning of measurements in Děčín. These series had to be reconstructed or digitized from the CHMI archive sources. Since 1851 we have been able to accurately identify the heights and sometimes even the specific days when the minima were marked. After thorough examination of field and newly measured data, as well as data obtained from review of older literature presenting the first surveys of marks on hunger stones already in 1842, older marks of low water levels can be considered mostly as a reliable indication of annual water level minima. The aim of the mark creators was not to make the commemorative inscription on drought, but to register the exact position of the water mark of the annual minimum. The deviations of most of the marks from the water gauge records did not exceed 4 cm, in worse cases 8 cm and only exceptionally the disparity was greater. From the material obtained so far, the overall slight downward trend of minima since the end of the 18th century is noticeable. The view on minima of the 17th and 16th century is based on only a few data and it is difficult to generalize so far. However, the minima obtained are comparable to or lower than the data from the critical dry periods of 1842, and 1858 to 1874. Our verification and certain rehabilitation of low water level marks should be an incentive to process all available epigraphic documents of this kind in the near future in closer cooperation with colleagues from Saxony. The potential of these objects offers a deeper knowledge of periods of hydrological drought and possibly morphological changes in the Elbe riverbed.