Calculation for horizontal models:

For each element (SPEI) or for each node (KSPE), a storage coefficient S [-] for an unconfined aquifer can be entered for transient calculations (S = S₀ * thickness m).

In the confined aquifer, the preset specific storage coefficient S₀ = S / thickness = 3.3 10^-6 [1/m] is used. This preset value can be changed during the input dialogue of the transient calculation.

For vertical and 3D models, the pressure formulation of the flow equation is used, and the storage coefficient is calculated from the variables:

• Pressure p,

• Saturation S_r,

• Density ρ,

• flow effective porosity n,

• Matrix and fluid compressibility α, β.

The standard compressibility of matrix (α) and fluid (β) are defined within the input dialogue of the transient calculation.

Normally, the porosity entered via PORO is used to calculate the specific pressure storage coefficient for the variable n [-].

If no storage coefficients and no porosity have been specified, 0.2 is used as the default value..

Structure of the transient input file