Water Supply: Defining the Stress Period

This model has a single, transient, stress period with a duration of 36 hours or 180000 seconds. The stress period has 10 steps with a time step multiplier of 1.414.

Select Model|MODFLOW Time... In the MODFLOW Time dialog box, verify that the time unit is seconds. Then change the starting time to 0 and the ending time to 180000. Change the Multiplier to 1.414 and change Steady State to Transient.

In the MODFLOW input files, the number of steps is specified but in the ModelMuse, the number of steps is calculated. This facilitates setting up stress periods automatically when boundary conditions change. To get the right number of time steps, the user can try different values of Max first time step length. A value of 2000 will give the 11 time steps. Another option is to click the "F()" button that appears in the cell for Max first time step length. This will cause the Time Step Length Calculator to appear. You can enter the number of time steps in the dialog box and it will calculate the appropriate value for the length of the first time step.

Make sure that Drawdown reference is not checked. When Drawdown reference is checked, the heads at the end of the stress period are used as reference values when calculating drawdown. Usually, this option is used with a steady state stress period used to set the initial conditions before the beginning of a transient simulation.

Click OK to close the dialog box.