On spatiotemporal drought classification in New South Wales: Development and evaluation of alternative techniques

Abstract

The identification, monitoring and characterisation of drought are of importance in water resources management and planning in Australia. The predominance of agriculture and water-rich activities on the eastern seaboard of Australia and the susceptibility of these industries to drought events makes an understanding of the spatial and temporal characteristics of drought significant to long-term water resources and agricultural planning. To assist in the quantification of the risk of the spatial extent of drought, the Standardised Precipitation Index (SPI) and system of percentiles were used to characterise the frequency, severity and spatial extent of drought incidence in 30 meteorological districts of New South Wales (NSW), Australia, for the period 1913-2002. Monthly district rainfall was aggregated on 1, 2, 3, 6, 9, 12 and 24-month time scales, and characterised by SPIs and plotting positions for each phase. To assist in determining the spatial and temporal relationships of drought in NSW, drought severity-area-frequency curves were developed, enabling an assessment of the severity of drought throughout the state. Results obtained were contrasted with historical drought years to show the relationship between the severity and spatial extent of drought events, as well as distinguishing short, medium and long-term drought in NSW. The two methods of drought identification are evaluated against several substantive criteria and recommendations for future practice given.