Abstract:Four physical models were designed, built, and put into operation for the information centre „Erlebniswelt Grundwasser“ of the “Landeswasserversorgung” in Langenau. The models illustrate the following physical principles:
(1) Darcy’s – Law:
The model visualizes the law formulated by the French hydraulic engineer Henry Darcy. Henry Darcy observed with a similar experimental set-up that the total discharge of water through a cross-sectional area of a porous medium is directly proportional to the hydraulic conductivity and the pressure drop and inversely proportional to the flow length.
The model consists of a rectangular container made of glass and stainless steel and four horizontally grouped cylinders made of glass. Three of the cylinders are packed with different kinds of soil, one cylinder is empty. At the push of a button by a visitor a constant water flow is applied to the four cylinders. Due to the different pressure drops within the four cylinders different water levels adjust in the four vertically arranged reservoirs made of glass. The difference in water level between the inlet container and the four reservoirs visualizes the different pressure drops within the different kinds of soil. After an adjustable time the pump switches off automatically. The exhibit can then be started again by a visitor.
The model serves as a visualization of the flow resistance in different subsurface materials.
The set-up consists of three rectangular cylinders made of stainless steel and glass. The cylinders are packed with coarse sand, fine gravel, and a whole-core sample from karst, respectively. At the push of a button by a visitor the same amount of water is applied to each of the three cylinders. While the water flows through the cylinder packed with the whole-core sample from karst very quickly due to the low flow resistance of the subsurface material it takes a considerable amount of time for the water to flow through the fine gravel and even more so through the coarse sand.
(3) Lifting Pipe:
This model visualizes a groundwater withdrawal using a lifting pipe.
From a battery of wells water is pumped into a collecting sewer located at a lower elevation than the water level in the wells using a lifting pipe. After the lifting pipe is initiated by a compressor water is transported from all connected wells to the collecting sewer without any further energy consumption.
The model displays an aquifer with three wells and a collecting sewer. By means of a circulation pump and an overflow tank a constant water level is adjusted in the model aquifer. Water is pumped from the three wells to the collecting sewer using a second pump until the lifting pipe is initiated. Then the pump is switched of automatically using a time-delay relay. Due to the siphon effect the water keeps on flowing towards the collecting sewer although the pump is switched off.
(4) River Water Infiltration / Groundwater Extraction:
The model displays a fluvial topography and an aquifer with an extraction & infiltration well.
River water is infiltrated into an aquifer by a well and after a passage of several hundred meters in groundwater flow direction the water is extracted at a second well. By the passage through the aquifer the river water was purified and can easily be treated for drinking water supply.
In the set-up a constant water level in the river is adjusted using a circulation pump and an overflow tank. Water is pumped from the river into the infiltration well. By a second pump water is extracted from the aquifer and infiltrated back into the river. Between the infiltration and extraction well a groundwater level adjusts according to the flow resistance of the aquifer.
Further information concerning the information centre „Erlebniswelt Grundwasser“ of the „Landeswasserversorgung“ in Langenau is available at