The interblock transmissivities are calculated as the harmonic mean of the adjacent blocks. Driving forces on the system are external hydrologic conditions of recharge from precipitation and fixed hydraulic head boundaries.
Density is considered constant in space.
Input of hydraulic conductivity and porosity is either given per layer per zone, where each zone represents an area of uniform parameters, or per individual cell. There are up to 9 zones allowed in the model. Finally, a 'log' file is created with information on simulation progress. It runs in a DOS window under MS Windows 3.1. The documentation includes installation instructions and a user's manual.