Frosty temperatures, cold winds, sometimes clear skies and fresh snow from time to time: layers of ice quickly form on the lakes, ponds and reservoirs. But even if the icy surfaces are tempting for ice skating, the City of Aachen's Climate and Environment Department warns emphatically that entering all water surfaces in Aachen's parks is extremely dangerous and is always at your own risk. This warning applies to all ponds in the city area. In the case of fenced-in ponds, such as the Diepenbenden or Kupferbach dams, access is even completely prohibited.
Even after several consecutive nights of sub-zero temperatures, the dangers of ice skating should not be underestimated. There is a risk of collapsing, especially in open water. According to experts, layers of ice are only considered safe if they are at least 15 centimetres thick. For flowing water, the minimum thickness is 20 centimetres. The ice thickness is and remains very thin at the inlet and outlet points.
And the fenced-in dams in particular pose a great danger, otherwise there would be no fencing or warning signs. Steep banks and rapidly changing water levels during rainfall can cause the ice to break or form treacherous cavities under the ice. The yellow warning signs on these bodies of water are valid throughout Europe due to an EU standard and indicate the "Danger of falling/deep water".
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.