The mining industry has caused an increase of the groundwater level in many cultivated areas, so that the groundwater level is often too near to the surface. To avoid damage at existing buildings controlling the groundwater level with withdrawal wells is necessary. In contrast to wells, used for groundwater winning, the pumping rate of local drain wells is often unknown. So they cannot be considered as boundary condition KNOT. More important than the pumping rate is the altitude of the groundwater subsidence. The following describes the modelling of such a situation with SPRING.
The figure shows schematically the problem:
Schematic representation of a polder measurement in the basement of a building
VORF
The FE node of the drain well gets the attribute VORF, its value corresponds to the maximum admissible altitude of the groundwater level (e.g. basement foundations - 0.8 m). In a 3D model it is sometimes necessary that the FE nodes in the filter area of the drain well get the attribute GLEI. This depends on the vertical discretization of the FE net. In this case the attribute VORF has to be assigned to one of these nodes.
LEKN
Additionally to the attribute "VORF" the leakage coefficient LEKN must be assigned to the FE node of the drain well. A very great value of the attribute "LEKN" acts like the fixed potential head "POTE". This guarantees keeping the requested altitude of the groundwater level. If pumping rates of the drain well exist the leakage coefficient can be calibrated by comparing the measured and calculated rates.
In SPRING you can assign the calculated pumping rates to any attribute (e.g. KKKK) with Attributes 
Import result data, selection of the background file "aaa" and selection of "Leakage rate (m³/node/TU)". With Attributes Edit nodes Capture all attributes of the node are listed, including the pumping rate.
MXKI
If the groundwater level is below the defined value of "VORF", the drain well infiltrates into the groundwater. To prevent that the attribute "MXKI = 0.0" has to be assigned to the FE node of the well.
MXKE
Sometimes it is necessary to limit the pumping rate to a maximum, e.g. to consider the capacity of the drain well. In this case the attribute "MXKE" [m³/TU/m] defines the maximum possible pumping rate. Attention: Taking water out of the model requires a negative value!