Using and Testing Drought Indicators

Abstract

Several drought indices have been applied to different hydrological time series relevant to droughts in the Community of Madrid and its water supply system, managed by public company Canal de Isabel II (CYII). Results have been studied in order to establish how much useful information can be drawn from them with emphasis in its diagnosis ability and anticipation capacity.

The set of studied drought indices involve variables as precipitation, temperature, flow and simulated water storage. Their performance has been tested at monthly, seasonal, annual and biennial levels.

The widely known Standardized Precipitation index (SPI), and the so called SQI and SRI, (an attempt to extend the SPI approach to total inflow and water storage level), along with the Reconnaissance Drought Index, or RDI (Tsakiris, 2004) make up the family of standardized indices which have been studied in the first place. The Run Method as it has been proposed in Cancelliere et al. 2005 and the Palmer Drought Severity Index, or PDSI (Palmer, 1965) complete the set of studied indices.

The general descriptive power of drought indices is widely confirmed by the study. Indices efficiently characterize historical droughts and provide straightforward means to compare their severity in objective, general terms. Capability of the Run Method to provide sound values of return period for actual or hypothetical droughts is acknowledged.

The ability to foresee droughts or their future evolution provided by indices has been investigated. Finally, the potential utility of the indices in management of droughts and decision making has been considered.