When creating a groundwater model, some nodes have the same potential head, but the value is unknown. This is valid for:

 

surface waters in horizontal and three-dimensional models,

along the wetted boundary of a vertical well in a vertical model,

as a boundary condition for the border line between a two-dimensional and a three-dimensional area,

the nodes of a well below each other in a three-dimensional model.

 

For all nodes defined with GLEI, the calculation obtains the same value for potential head. Numerically, the equations for these nodes are summed to one equation. They are considered as one unknown value.

Therefore, in three-dimensional models, no different exfiltration rates over the depth of a vertical well are required. The complete exfiltration rate can be assigned to one node. This is not valid for the case of several pumps with different extraction rates over the depth. Only in case of a constant pumping rate can the total extraction rate be assigned to any one of the nodes.

 

Realization in SPRING