Concrete dams, which do not have any steel reinforcement, have a much longer service life than reinforced concrete struc-tures exposed to weather. The oldest concrete dams are about 120 years old. masonry dams can be much older and still be in service.ut at the same time, it can also be very short if some of the safety-relevant elements are no longer functioning properly.an example for uncontrolled safety decrease is the 272m high Enguri arch dam (the worldâs highest arch dam) in Georgia, which was completed in 1984.
As it turns out, mosquitoes do play an important role in a variety of ecosystems. For example, each year when the snow melts in the Arctic tundra, mosquitoes hatch from their eggs and make up a significant part of the biomass. Some scientists believe these insects serve as an important food source for migratory birds.
Diseases on the Inside When insects harbor viruses, bacteria, or parasites inside their bodies, they can spread disease a second way by passing it on through a bite or other means. Only a small percentage of insects transmit disease to humans in this way.any insects feed exclusively on plants, while certain ones eat other insects. Houseflies carry disease-causing agents on their feet Of course, there are insects that annoy man and beast with their painful bite or simply by their presence in vast numbers. Some also wreak havoc on crops.