AN EARLY WARNING SYSTEM FOR DROUGHT MANAGEMENT USING THE PALMER DROUGHT INDEX

The Palmer Drought Severity Index (PDSI) is used in a non-homogeneous Markov chain model to characterize the stochastic behavior of drought. Based on this characterization an early warning system in the form of a decision tree enumerating all possible sequences of drought progres sion is proposed for drought management. Besides yielding probabilitie s of occurrence of different drought severity classes, the method asso ciates a secondary measure in terms of likely cumulative precipitation deficit to provide timely guidance in deciding drought mitigation act ions. The proposed method is particularly useful for water availabilit y task forces in various states for issuing drought warnings in advanc e. The applicability of the technique is illustrated for the Tidewater climatic division of Virginia.