The following parameters are required as data basis for the following calculation:
Main water course system: Water levels in m (in most cases m above sea level) at least at two points: fixed potential boundary
POTE

Secondary water course system: Water level in upper reach (m), if required, discharge measurements for determination of leakage
VORF and LERA

Groundwater recharge: Precipitation, soil type, soil use, gradient for calculating recharge
FLAE (mm/time unit of the model file)

Ground level surface:
GELA, and, if required, data on an impermeable layer in the underground
UNTE, otherwise calculation using the thickness


Remark: The time unit of the model file is set when you create a new project (File New).
These data can be delivered by the following sources:

Ground level elevations and TIFF-files: Land Survey Office, Land Registry

Groundwater measuring points, levels on water courses: Federal environmental office, water boards, water works, etc.

Withdrawals: Well operators

Geology: geological maps, exploration drillings, pumping tests

Leakage: for example calculation via K values of the surroundings and discharge measurements

Groundwater recharge: for example on the basis of RVR data, according to Schroeder and Wyrwich or Meßer
Determining the model boundaries