Expected Highest Groundwater Level (EHGL) 2022
The EHGL map (2021) covers about 90 % of the area of the State of Berlin. The expected highest groundwater level is represented by lines of equal height in metres above sea level. The difference in height between groundwater isolines is 0.1 m. Thus, the map shows the distribution of the observation well levels in the EHGL case. In the areas of the glacial valley and the Panke valley, the uppermost groundwater is predominantly unconfined, in the area of the plateaus it is mostly confined or covered. It is evident from the course of the contour lines that the Spree and the Havel and their tributaries form the receiving waters for the groundwater close to the surface. The groundwater flow direction lies perpendicular to the contour lines from the higher to the lower level. The EHGL varies between about 61.9 m above sea level on the state border of the north of the Barnim Plateau and 30.1 m above sea level where the Lower Havel exits the state area in the southeast. The closer clustering of the contour lines in the Panke valley, the Teltow Plateau and the Nauen Plate as well as in the south-eastern section of the Barnim Plateau shows that, as expected, the height gradient of the groundwater is larger here than in the glacial valley. Thus, the course of the EHGL isolines paint a plausible picture for the case that neither groundwater extractions nor artificial groundwater replenishments occur. In particular, this map provides realistic EHGL values in the area of the large cones of depression of the Berlin waterworks, which could hitherto only be estimated very roughly without the modelled groundwater levels (cf. current groundwater levels maps, on which the cones of depression are visible).
On the digital map, you can display the EHGL value for a specific location by a mouse click.
In the vicinity of the shores of the Spree, the upper Havel and the Tegeler See, there are lateral riparian strips (see also Methodology). These areas are marked with different colours according to the EHGL value and can also be displayed by a mouse click.
A user can therefore easily access an EHGL value relevant to their question.
The following should be noted:
The map value applies to the groundwater level of the uppermost aquifer. In the area of the glacial and Panke valley, the uppermost aquifer is predominantly unconfined. Thus, the map value generally specifies the height of the groundwater surface here, which is relevant, for example, for dimensioning waterproofing for buildings.
However, in some places – often in the plateau areas – overlying layers with low water conductivity, such as boulder clay and boulder marl, clay, silt and organic soils, cause the groundwater to be confined. In these cases, the map does not specify the height of the groundwater surface, but rather that of the piezometric surface of the confined groundwater.
In these cases, shallow groundwater (in the sense of the groundwater definition of DIN 4049) may form – possibly only temporarily – above the confining layers. This stratum water is also water under pressure in a constructional sense and must be taken into account in relevant contexts.
Due to the scale and the rather heterogeneous sedimentation conditions in certain situations, the two possible deviations from the usual hydrogeological configuration that were mentioned cannot be represented at all or not fully in the Geological Outline provided. However, they can be revealed in the course of soil investigations, which are a prerequisite for all construction activity. In addition, the strata log sheets from the database of the State Geological Service (only in German) can be accessed on the Internet for each individual case.
It should also be noted that the EHGL may be above ground level. In this case, the formation of groundwater ponds cannot be ruled out.
Near surface waters, in addition to high groundwater levels, short-term local flooding may occur, which cannot be inferred from the EHGL map. Information in this regard is available under Hochwasser (floods, only in German).
Current water levels of the Berlin State monitoring network of surface waters and the groundwater can be researched in the water portal of the Senate Department. Furthermore, State-wide analysis results are provided as part of groundwater isoline plans for the main aquifer and the Panketal aquifer for the month of May.
Should the current groundwater level be only slightly lower than the value of the EHGL map, or even slightly higher, which is very unlikely in the glacial valley but cannot be entirely ruled out, this may be due to the different statistical bases of the maps. In these cases, more detailed information may be requested from the State Geology Working Group.
In the Panke valley, in particular in its northern part, the groundwater measuring points are sometimes relatively far apart considering the heterogeneity of the aquifer and the predominantly large natural groundwater gradient. As a result, the EHGL map is more fraught with uncertainty here than in the area of the glacial valley. This also applies to areas in the immediate vicinity of surface waters (the Panke and its small tributaries). While this was accounted for by the above-mentioned increments, localised deviations of the map value from an actually occurring highest groundwater level cannot be entirely excluded. If new investigations (drillings, groundwater level measurements) yield results in such areas that clearly contradict the EHGL value of the map (current groundwater level is higher than the map value or lower within the metre range), the EHGL should be modified locally by an expert. In such cases, please notify the State Geology Working Group.
The hydrogeological conditions in the area of the Teltow Plateau, the Nauen Plate and the Barnim Plateau are considerably more complicated than those in the glacial valley and the Panke valley. Therefore, the mathematical EHGL estimate, applying the methods described above is fraught with somewhat higher uncertainties. To be on the safe side, the map was thus developed to indicate EHGL values that are rather higher than those that may actually occur. This was deemed a reasonable approach in construction planning. It should also be noted here that the probability of locally occurring stratum water atop confined layers at heights above the indicated EHGL values is greater than in the glacial valley. Should you detect contradictions to the map in the framework of future investigations (e.g. a soil investigations), please also inform the above-mentioned authority.
It is envisaged that the map will continue to be checked and possibly modified based on the results of the Berlin State Geology Working Group and new scientific findings. The intent is to recognise and take into account possible changes in the hydrological conditions that cannot currently be foreseen (e.g. due to general changes in the climate) as soon as possible.