User's guide of Proceessing Modflow 5.0

Processing Modflow 73
3.5 The Parameters Menu
Time
Use the Time Parameters dialog box (Fig. 3.16) to specify temporal parameters, including the
time unit, the length of stress periods and the numbers of stress periods, time steps and transport
steps. The table and the elements of this dialog box are described below.
Fig. 3.16 The Time Parameters dialog box
< Period, Active, Length, Time Step: In MODFLOW, the simulation time is divided into
stress periods, which are, in turn, divided into time steps. Check the Active flag to activate
a stress period. For each stress period, you have the option of changing parameters associated
with head-dependent boundary conditions in the River, Stream, Drain, Evapotranspiration,
General-Head Boundary and Time-Variant Specified-Head Boundary packages, as well as the
recharge rates in the Recharge package and pumping rates in the Well package. For transport
simulations, you can change source concentration associated with the fluid sources and sinks.
The length of stress periods and time steps is not relevant to steady state flow simulations.
However, if you want to perform transport simulations at a later time, you must specify the
actual period length.
< Multiplier (FLOW): MODFLOW allows the time step to increase as the simulation
progesses. It uses the following formulae to increase the lengths of time steps as a geometric
progression.
3.5 The Parameters Menu