Anyone who steps onto the ice of freely accessible ponds - should a layer of ice ever form on Aachen's pond facilities, this is always at your own risk! Frosty temperatures, sunshine and hardly any snow - the first thick layers of ice have already formed on the lakes. This is actually the ideal weather for gliding across the ice on skates.
Nevertheless, people are warned not to step onto the ice. This warning applies to all ponds in the city area. In the case of fenced-in ponds such as the Diepenbenden or Kupferbach dams, ice sports are even prohibited.
Even after several consecutive clear nights with temperatures well below zero, the dangers of ice skating on Aachen's ponds should not be underestimated. There is a risk of collapse, especially in open waters. According to experts, layers of ice are only considered safe if they are at least 15 cm thick; for flowing water, the minimum thickness is 20 cm. The ice thickness is and remains very thin at the inlet and outlet points.
The fenced-in pond facilities pose particular dangers, otherwise there would be no fencing or warning signs. The yellow signs are valid throughout Europe due to an EU standard and point out the danger of falling/deep water. This is due to steep banks and rapidly changing water levels during rainfall, which can lead to the ice surfaces breaking or form treacherous cavities under the ice surfaces. There is currently a particular risk at the Kupferbach dam, as the water level is rising every day following completion of the repair work.
Fish also live in many of Aachen's ponds. A large number of skaters startles the fish out of their hibernation, their metabolism is boosted and their breathing intensifies. This leads to higher energy and oxygen consumption and puts an enormous strain on the fish's energy balance. In the following spring, they often die without symptoms if they lack the energy they need to compensate for the stress situations associated with rapidly rising temperatures.