Groundwater
Groundwater fills the cavities in the ground. The layers that carry groundwater are aquifers. Depending on the nature of the subsoil, a distinction is made between pore, fissure and karst aquifers.
As part of the natural water cycle of precipitation, evaporation and runoff/infiltration, groundwater is formed by infiltrating precipitation, remains underground, flows into surface waters or comes to the surface as a spring. During longer periods without precipitation, streams, rivers and lakes can be fed exclusively from groundwater.
Natural groundwater contains no germs or pollutants and, as managed groundwater, is the preferred source of drinking water. Almost 70 % of drinking water in Germany is obtained from groundwater.
The groundwater conditions in Aachen are basically divided into near-surface groundwater and deeper groundwater, most of which occurs as fissure groundwater in the Devonian and Carboniferous bedrock.
The near-surface groundwater is generally found in the Cretaceous and Quaternary unconsolidated sediments and exhibits only minor flow conditions and seasonal or weather-dependent differences in the depth of flow. Locally, there are also isolated, more or less horizontally limited occurrences. The basic flow direction in the urban area largely follows the topography in a north-easterly direction. The watercourses serve as receiving waters, mainly the Wurm and Inde rivers, which also tend to drain in a north-easterly direction. The near-surface groundwater flow in the settlement area is also influenced locally by the sewage system and domestic drainage.
The deeper groundwater is divided into several groundwater bodies, essentially the southern Limburg chalk table and the Aachen-Stolberg limestone ranges and in the north the main terraces of the Rhineland. The main groundwater flow direction is northeast in accordance with the Variscan-Rhenish strike.
Three groundwater works (Brandenburg, Eicher Stollen and Schmithof) with their corresponding surrounding protected areas are located in the rich limestones of the Aachen-Stolberg limestone formations. The two parallel thermal spring trains (Aachener Zug and Burtscheider Zug), from which the Aachen thermal springs emerge at certain points, belong to the same formation.
The Reichswald waterworks with its protected area, which extracts groundwater from tertiary sands, is located in the main terraces of the Rhineland in the north-east of Aachen.
The protected areas make up around 5% of the city area and are divided into protection zones I, II and III, in which various strict protection measures apply.
Groundwater conditions are recorded via groundwater measuring points, which are carried out by the authorities or by private parties - usually by experts.
Groundwater extraction
Groundwater is extracted for various purposes in many areas of the city of Aachen. For example:
- Public water supply
- Industrial process and service water
- Supply of agricultural farms and individual buildings in the outdoor area with process and drinking water
- Irrigation / drainage of agricultural or horticultural areas or other green spaces
- Groundwater remediation in cases of damage, usually in contaminated areas
- Groundwater lowering during construction work, e.g. the erection of buildings
The extraction and pumping of groundwater generally requires a permit under water law, which must be applied for from the water authority.
Plans
A map of areas where it is not possible to infiltrate properly can be viewed on the homepage in the online geoinformation system. The same map also provides an initial guide for the extraction of groundwater. This is because it can be assumed that there is not enough water available for garden irrigation in areas where infiltration is not possible.
Responsible authorities:
Groundwater drainage during construction
Construction dewatering (groundwater extraction during construction) is used to temporarily drain an excavation pit. Construction measures in groundwater must be designed in such a way that there are no adverse effects in the vicinity of the construction measure (e.g. trees, natural monuments, subsidence of buildings). Construction dewatering is a use of water for which a permit under water law is required.
It is recommended that the type and scope of the dewatering / lowering of the groundwater level be clarified in advance with the lower water authority, as investigations may have to be carried out before the construction project is started. It may be necessary to set up groundwater measuring points.
The groundwater extracted from the excavation pit must not be pumped into surface water (open dewatering). It must be discharged into the public sewer system, as the geology in Aachen always causes the water to become turbid if it is discharged into surface water. If other dewatering methods are chosen, e.g. vacuum dewatering, discharge into surface water may be permissible; in these cases, the application for permission to discharge into a body of water can be made together with the application for permission to extract groundwater.
Discharge into the public sewer requires a separate permit from the City of Aachen. At the same time, the discharge point into the public sewer system must be assigned. The withdrawal/discharge quantity into the sewer must be recorded.
Competent authorities: