Stress Period Qualities The Stress Period Qualities window has two varieties; one displayed when you select the Add Stress Period command and the other displayed when you select the Stress Period Qualities command, both under the Stress Periods menu. Both of these varieties share similar characteristics, including setting whether or not a particular stress is active during a given stress period and setting the duration, the number of time steps, and the time step multiplier for a stress period. Note that the frame for a stress is only enabled if you have selected that stress in the Basic Information window. If you select the New Stress option button, Graphic Groundwater expects you to set a value for that stress period in an overlay. If you do not, the stress is not implemented in MODFLOW. In other words, the code will ignore the stress during that stress period. If you are adding a stress period, the Stress Period Qualities window includes an Add button. The version of the Stress Period Qualities window implemented when you execute the Stress Period Qualities command under the Stress Periods menu includes a Delete button and a Period drop down list. The stress period indicated in the Period drop down list is the one that will be deleted if you click on the Delete button. A warning message is displayed before any stress period is deleted. You can navigate between stress periods by using the up and down arrow key when the Period drop down list has the focus (a control gets the focus when you click on it).