How is an aquifer

BGR Federal Institute for Geosciences and Raw Materials

Fig. 1: Public water production in Germany in 2016 according to DESTATIS Source: BGR

In Germany, groundwater is an essential and indispensable good. For over two thirds of the population it is the sole source of daily water needs. Like the total water flow, the groundwater flow has also been falling for years. According to the Federal Association of Energy and Water Management (BDEW), the annual groundwater extraction (including spring water) by public water suppliers has been falling continuously since 1990 from 4.79 billion m³ and has been more or less at 3.60 billion m³ for several years leveled off. With a total delivery volume of the public water supply in 2016 of 5.20 billion m³, groundwater and spring water account for a good 69% (Tab. 1).

In addition to the 3.60 billion m³ of groundwater extraction by the public utilities, the non-public water utilities gained 2.36 billion m³ of groundwater and spring water in 2016. Mining and quarrying of stone and earth accounted for 1.14 billion m³ of this, manufacturing 0.73 billion m³, agriculture and forestry, fishing including irrigation associations 0.23 billion m³, energy supply 0.08 billion. m³, water supply, sewage and waste disposal 0.08 billion m³ and the other branches of the economy 0.09 billion m³. With a total delivery volume of the non-public utilities in 2016 of 19.23 billion m³, groundwater and spring water only account for 12.3% (Tab. 2).

In 2016, a total of 5.96 billion m³ of groundwater (including spring water) was extracted in Germany. This corresponds to around 12% of the average newly formed groundwater of 48.2 billion m³ (Fig.Mean water balance in Germany 1961 - 1990) and amounts to 16.2 mm in relation to the area of ​​Germany.

Fig. 2: Non-public Water production in Germany in 2016 according to DESTATISSource: BGR

The groundwater extraction rates of the public (Fig. 1) and private water supply (Fig. 2) vary considerably from state to state, as do the numbers in Table 1 and Table 2 clarify. In Bremen, Hamburg, Schleswig-Holstein and Saarland, the public water supply is almost 100% based on groundwater and spring water, followed by the states of Brandenburg (96%), Bavaria (90%), Hesse (88%), Lower Saxony (87%) %) as well as Rhineland-Palatinate and Mecklenburg-Western Pomerania with 84% groundwater and spring water. In a country comparison, Thuringia (56%), North Rhine-Westphalia (42%), Berlin (29%) and Saxony are at the lower end with 27% groundwater and spring water in the public water supply. Berlin gets a large part of its drinking water from bank filtration, the states of Saxony and Thuringia cover almost half of their drinking water requirements from lakes and dams.

In the non-public water supply, groundwater plays a relatively minor role. As a rule, river water dominates here, which is mainly used for cooling purposes in energy production companies. Only in Saxony (68%), Brandenburg (55%) and Mecklenburg-Western Pomerania with 47% does the groundwater and spring water share in the non-public water supply exceed the river water share.

Fig. 3: Groundwater resources in Germany by type of GW ladder Source: BGR

In absolute terms, Bavaria is well ahead of the federal states of North Rhine-Westphalia with 502 million m³, Lower Saxony with 482 million m³ and Baden-Württemberg with 476 million m³ in terms of public water supply with annual groundwater extraction (including spring water) of 779 million m³ (Tab. 1). When it comes to the non-public water supply, North Rhine-Westphalia clearly stands out with 890 million m³ of groundwater and spring water due to the water-intensive steel, chemical and mining companies located there. This is followed by Brandenburg with 274 million m³, Bavaria with 267 million m³, Saxony with 239 million m³ and Lower Saxony with 221 million m³ of ground and spring water extraction (Tab. 2).

The groundwater resources in Germany are regionally unevenly distributed, depending on the geological subsoil and the hydrogeological conditions. The Figure 3 shows in generalized form their near-surface distribution, differentiated according to cavity type, extent and productivity. According to this, around 40% of the land area has pore aquifers, some with very significant groundwater resources. About 21% of the area is occupied by fissured and karst aquifers. In the rest of Germany, the subsoil is built up by porous or fissured groundwater scumbars that only have local and limited or no significant groundwater resources.

Fig. 4: Productivity of groundwater resources in Germany Source: BGR

The largest contiguous area with rich groundwater resources is the North German Plain, which is mainly built up by thick sands and gravels of the Quaternary and Tertiary ages. Particularly important here are deposits that are formed near the surface in the course of the glacial valleys or in deep gullies formed during the Ice Age. The loose rocks of the Quaternary and Tertiary of the Alpine Foreland also form extensive and productive pore aquifers. Furthermore, the entire Upper Rhine Rift is one of the areas with very abundant groundwater resources. In the Lower Rhine Bay and in the Lower Rhine Plain, mighty pore aquifers, some of which are superimposed and are rich, form some of the most important groundwater resources in Germany. In the above-mentioned, significant and very productive deposits, there are usually the large groundwater-promoting works of the public water suppliers, such as the Figure 4 shows.

In the low mountain ranges there are regionally significant groundwater resources with higher productivity in the limestone formations of the Swabian and Franconian Jura as well as in Thuringia, in the shell limestone between the Main and Black Forest and the chalk of East Westphalia (karst aquifers), in the mighty sandstones of the Palatinate Forest, Black Forest, Spessart and Solling and last but not least in the basalt of the Vogelsberg (fissured aquifer).

Low mountain ranges such as the Rhenish Slate Mountains, the Harz, Thuringian and Bavarian Forests, the Ore Mountains and the Black Forest are mostly made up of rocks such as clay slate, crystalline slate and deep rock. Sandy-gravel valley fillings and rubble fans at the foot of the mountains as well as the locally embedded deposits of karstified limestone and dolomite rocks in the slate mountains can be used as local groundwater resources.

A comprehensive description of the regional groundwater conditions in Germany is provided by the joint publication of the State Geological Services (SGD) and the BGR with the title "Regional Hydrogeology of Germany - The Groundwater Aquifers: Distribution, Rocks, Storage Conditions, Protection and Importance".