Chapter 12 Monitoring Drought Using the Standardized Precipitation Index

Because drought is so difficult to define, detect, and measure, researchers have been striving to develop indices to accomplish these tasks. The importance and historical development of drought indices for monitoring drought is emphasized in the chapters by Redmond (chapter 10) and Heim (chapter 11). The goal of a drought index is to provide a simple, quantitative assessment of three drought characteristics: intensity, duration, and spatial extent. A drought index should also provide a historical reference that can be used to compare current conditions with past conditions