Attribute: GLEI [-] (node-wise)

To determine the position of a potential isoline (groundwater level) whose value is unknown, the GLEI attribute is assigned to nodes which will then all receive the same potential value in the model calculation.

• For vertical models, this is useful for abstraction wells whose abstraction rate is either known or varied. All nodes of the well that is located beneath the water level should have the same potential. These nodes are assigned a GLEI value of 0.

• For horizontal models, the data type GLEI can be specified at the shore nodes of a lake if the water level of the waterbody changes depending on the groundwater level or is unknown.

• In 3D models for example, the same potential heads are applied to fully penetrating wells. In this case, the potential head should be the same over the full length of the well.

• Along the connecting boundaries of coupled 2D-3D models, unknown equal potential heads are used to define the equal potential heads over the full thickness of the boundary (see chapter 2D/3D model structure).

All nodes in a single definition of GLEI have the same potential. A single definition is complete if no continuation of listed nodes follows (column 80 = blank, see example below).

The first value (columns 1 to 14) can be used to specify a constant potential head difference between two nodes [in meters]. The potential heads themselves remain unknown, however, they are determined in such a way that the difference between the calculated potential heads is equal to the prescribed value. In the example below, the potential heads will be calculated and assigned with zero difference between them to all of the nodes in the list, such that each node receives the same exact potential head value.

Example:

GLEI ks3 : nodes with equal unknown potential heads

0.00000 64- 65, 67, 66, 69, 68, 71- 73,

0.00000 75, 74,

In the example above, the nodes from 64 to 69 and 71-73 have the same potential head difference. Nodes 74 and 75 also have the same potential head difference, but this does not have to match the calculated potential head of the other nodes. Thus, nodes 64-69 and 71-73 will receive the same calculated potential head value, and nodes 74 and 75 will receive their own estimated potential head value. Several different data sets can, therefore, be entered.