Topic summary
Sewer system
Extracted from the Wikipedia article Sewerage.
Water table
Sewer system infrastructure often reduces the water table in areas, especially in densely populated areas where rainwater (from house roofs) is directly piped into the system, as opposed to being allowed to be absorbed by the soil. In certain areas it has resulted in a significant lowering of the water table. In the example of Belgium, a lowering of the water table by 100 meters has been the result. The freshwater that is accumulated by the system is then piped to the sea. In areas where this is a concern, vacuum sewers may be used instead, due to the shallow excavation that is possible for them.