Triggering mechanisms can be developed by authorities for imposing and terminating regulations during droughts. This article reviews the triggering procedures used by seven states and two interstate commissions. Although triggering mechanisms differ in degree of detail and regulatory flexibility, all of the procedures examined provide a set of well-defined responses that are activated when predetermined conditions are reached. Each plan discussed has been molded to fit local and state conditions, and each demonstrates the importance of coordinated planning for water shortage management prior to the onset of crisis conditions. Includes 10 references, tables, figure.