In a 1D calculation this record should be given value of the groundwater level. The groundwater is below that -value.
In a 2D calculation this record should be given sets of which specify the level of the groundwater at several locations; In 2D you need to give the sets as follows:
In 3D the phreatic line is specified as follows. Denote the lowest x with x_0, the next higher x with x_1 etc. Denote the lowest y with y_0, the next higher y with y_1 etc. Denote the phreatic level z value for x_i y_j with z_ij. Then give the following:
In nodes above the phreatic level the pressure will be set to zero during the calculation.
As a special option in 2D and 3D, you can specify one value only, which sets a constant phreatic level of that value everywhere. In this special case, you do not need to specify groundflow_phreaticlevel_n.