rlc: Brunnentypen - Earthcache

General Remarks:

Wells and springs can be classified in several different ways. One possible classification scheme is to distinguish wells and springs according to the geological principle, how the water is supplied. This cache will show you three geologically different types of wells and springs (namely a groundwater well, a rheocrene spring and an artesian well), and will explain the underlying geological formations. First of all, however, a small explanation about the meaning of "well" and "spring": typically, a locally confined, naturally occurring groundwater emission is called "spring". On the contrary, a "well" is artificially erected. If a naturally occurring spring is "transferred" into a well, this is usually referred to as a "tapped spring". In the context of this cache, "wells" and "springs" are used equivalently.

Well 1: Groundwater Well (N 48° 53.087 E 009° 07.556)

Here you are standing in front of the sole remaining (of originally 23!) wells of the village of Möglingen, which were used for supplying drinking water to the inhabitants before 1906 (source on page 3; only in German).

Geologically, all of these wells have been groundwater wells. Hence, a well shaft or a tube has been lowered into the Earth's surface until the groundwater horizon was reached. In this area, the groundwater horizon lies around 2 m to 3 m below the surface. Thanks to the nearby Leudelsbach (a creek), the groundwater horizon was (and still is) quickly refilled, so that the extraction of even huge volumes of water has been unproblematic.

The geological conditions are shown in figure 1.

Well 2: Rheocrene Spring (N 48° 53.580 E 009° 07.900)

Here, you're standing in front of a special type of a rheocrene spring, namely in front of a so-called contact spring (to be absolutely correct: a tapped contact spring).

In the drainage area of rheocrene springs, the rainwater drains away into the water permeable soil. The major difference to a normal groundwater well is that for rheocrene springs, the water will reach a water impermeable layer at a certain depth. As the name indicates, the draining water cannot penetrate the water impermeable layer and will hence sit on this layer.

Depending to the shape of the water impermeable layer, one can further distinguish different sub-types of rheocrene springs. With the contact spring, the water impermeable layer is inclined. Therefore, the drainage water runs down the water impermeable layers just like along a children's slide. Approximately at the site, where the contacting surface between the water impermeable layer and the water permeable soil cuts the Earth's surface, the water is expelled to the surface: this forms the contact spring.

The geological conditions are shown in figure 2.

Well 3: Artesian Well (N 48° 54.092 E 009° 06.565)

Artesian wells are even more interesting. Here the draining water drains away into the water permeable layer, which is sandwiched between two water impermeable layers. Hence, the water within the water permeable layer cannot escape upward or downward. If the well lies below the drainage area, the water can be pressurised at the well's site, so that water can be expelled at a level, way above the ground surface. It is even possible that a fountain is formed.

The geological conditions are shown in figure 3.

The extension of an artesian system can be on a small scale (as it is the case at the present location). Some artesian systems, however, can extend over several hundreds of kilometres. As an example, the water of the mineral springs in Hoheneck (North of Ludwigsburg) originates from the Black Forest area. About 30,000 years lie between the drainage and the resurfacing of the water!

Important artesian systems supply parts of Paris and London with drinking water. Also, the Australian desert forms a large scale artesian system.

The Questions (Logging requirements)

1. Which obvious disadvantage has a groundwater well (well 1) for the user (as compared to a contact spring and to an artesian well)?
2. Which type of well is the groundwater well (the technical design)?
3. What fraction of rain water is evaporated, and is hence not collected by creeks or rivers, nor draining away? (See informational table close to the contact spring)
4. What is the approximate feed-rate of the artesian well ? (For doing a measurement, you can bring a 10 litre bucket and time the duration of the filling process.)
5. A picture of you or your GPS in front of the rheocrene well or the artesian well.

Please send me the answers in advance and wait for the permission to log.

A note for strollers/wheelchair users

When using appropriate ways, the cache is suitable for strollers and wheelchairs. However, wheelchair users will not be able to solve question 4 alone. If you contact me in advance, I will gladly give you another task.

As a route, I'm recommending well 1 – (N 48°53.084, E 9°07.621) - (N 48°53.251, E 9°07.628) - (N 48°53.361, E 9°07.687) - (N 48°53.429, E 9°07.706) - (N 48°53.552, E 9°07.651) – well 2 - (N 48°53.530, E 9°07.554) - (N 48°53.560, E 9°07.749) - (N 48°53.579, E 9°07.502) - (N 48°53.771, E 9°07.144) - (N 48°53.678, E 9°06.817) - (N 48°54.034, E 9°06.339) - well 3 and essentially returning the same route.

This route is flat, few cars are around and the road have a sealed surface (apart from a short part with a well maintained dirt track.