Reed, D.W. 2015a. How rare the ongoing drought? Proc. National Hydrology Conference, Athlone, Ireland, 17 November 2015, Paper 06, 12pp.
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Drought rarity assessment from monthly rainfall data is suspect. Estimates are cherry-picked, with raingauge, starting month and duration chosen to maximise the inferred rarity of the drought that a Water Company is experiencing. Yet the resource system is sensitive to a spectrum of droughts: not just one of this specific duration and starting month.
These difficulties are resolved in a new approach. Using complete historic rainfall series for 1887 to 1992 for 38 sites across Great Britain and Ireland, methods are presented for assessing and visualising the rarity of an ongoing drought.