The importance of historical maps for man-made pond research: From the past extent of ponds to issues of the present landscape. A case study from the Czech Republic

Historical maps are a valuable resource in landscape research. The information gathered from them facilitates the cognisance of landscapes and may assist current landscape planning. This study focuses on the historical occurrence and spatial extent of man-made ponds in the Czech Republic. Based on the 1^st Military Survey maps (1764–1783) of the Habsburg Monarchy, we use Historical GIS to identify 7,676 man-made ponds in the historical landscape. Compared to the 2^nd Military Survey maps (1836–1852), 56% of these man-made ponds had been drained. Such disappearances mostly affected large ponds in fertile agricultural areas, but also affected small reservoirs in less fertile areas at higher altitudes. As the current maps and spatial datasets (Water reservoirs, Landscape water regime, Farming areas) show, a number of these agricultural regions have been affected by climate changes and face water shortages. The historical map information of former ponds has the potential to contribute to their restoration in areas where water retention in the landscape needs to be increased.