Environmental Studies Program


Date of this Version

Spring 5-2011


Drought is a reoccurring phenomenon with widespread economic, social, and environmental impacts. Unlike other disasters, a drought cannot be easily detected. In addition, droughts are widespread and develop slowly over time making it difficult to detect its onset and monitor its severity and impacts. To assist in monitoring the severity and spatial extent of droughts, drought managers frequently use indicators and triggers. Drought indicators are meteorological or hydrological variables or indices that quantify or describe the level of drought severity. A drought trigger is a value of an indicator that initiates management and response actions. Despite the clear importance of drought indicators and triggers, they are not well understood and are often arbitrarily chosen. This is evidenced by the fact that many states in different climate regimes use the same indicators and triggers. Furthermore, stakeholders from across the country identified the need for a better understanding of drought triggers and indicators as a research priority.

The purpose of this research is to indentify spatial patterns of drought indicators and triggers. This was accomplished by identifying the types and numbers of indicators and triggers used in all currently available state drought plans. Each state’s indicators and triggers were then organized in a database and analyzed using ArcGIS software to identify the numbers of indicators and triggers used by each state as well as any spatial patterns. Results show that some patterns do exist and that the indicator or trigger used is not necessarily appropriate for the geographic location in which it is being used. Additionally, wide variability exists among the number of indicators and triggers used by each state. This information may help drought managers coordinate the use of critical indicators and triggers at the regional or basin level.