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Quite some time ago, I posted a colourful specimen of modern art and asked whether someone could tell what it is. One or two people seemed to like it, but couldn't add anything to my suggestion of the “Purple Woman Holding a Large Fish”.

So now the picture in its complete context:

Groundwater Map of Bavaria 1:25000, Section 6532 Nürnberg (1970).

The “Woman Holding a Fish” was in fact the spatial presentation of thicknesses and hydraulic conductivities of the upper groundwater storey¹ of this map sheet. The coloured areas and small squares show the structure and conductivity of the single aquifers.

Transmissivity

Colours indicate the transmissivites (thickness times hydraulic conductivity K; in Germany k_f), as is shown in the table in the right margin of the map:

Colour scheme for transmissivities.

Hydraulic conductivity (ranges for k_f at the bottom of the table) is mainly determined by aquifer type (unconsolidated vs. solid rock) and stratigraphy (indicated in the table head). Combined with thickness (in 10m intervals – table rows) you get the transmissivities. Darker colours mean higher transmissivity.

Spatial structure

The relation of the layers to each other is shown by bars and small squares. It is explained on the bottom right of the map:

Explanation of spatial representation.

The middle aquifer (Middle Keuper² – Burgsandstein, Blasensandstein) is represented by the continuous colour fill, with different shades of blue (see above). The Quaternary sediments form the upper aquifer, which is only present in some places (valley fills). This aquifer is shown as horizontal green bars that “float” above the middle aquifer plane. The bottom aquifer consists of the Lehrberg Layers of the Keuper in purple colours, onto which you can see “down” through the cut-out squares, or “windows”. In the west, there is now bottom aquifer (the Lehrberg Layers become clayey and act as an aquiclude), so no windows there. Finally, in a few places you have a perched aquifer on top, indicated by bars with a thick red line below (symbolising the local aquiclude).

Similar spaced-out designs can for example also be found in the (later published) Hydrogeological Map of the GDR 1:50000 (HK50):

Hydrogeological Map of the GDR 1:50000, main map.

1. Is this the correct translation for „Grundwasserstockwerk”, i.e. a group of (vertically stacked) aquifers? [↩]
2. Keuper is the Upper (Germanic) Triassic. [↩]