21st Century Drought Scenarios for the UK

Abstract

A 6-month drought severity index (DSI6) is applied to each of the 11-member perturbed-physics ensemble (HadRM3-PPE-UK) monthly precipitation dataset from 1950 to 2100 to investigate projected 21st century droughts in the UK. Four main drought characteristics are investigated: intensity, drought covariance, frequency of drought months and frequency of drought events at a given duration. Changes in these characteristics are analysed for 30-year periods: 1970-1999 (1980s), 2010-2039 (2020s), 2040-2069 (2050s) and 2070-2099 (2080s) and described in terms of their seasonal behaviour, for both moderate and extreme droughts. Projections of drought characteristics are expressed in the forms of ensemble-mean change relative to the 1980s and model consensus, and analysed over 23 water resource regions. In general, drought characteristics show profound increases (and widespread) for the 2050s and 2080s with larger change occurring during the wet season and under moderate drought conditions. Drought covariance sees greater increase during the dry season with greater change magnitude (but less widespread) under extreme drought conditions. Results also show that droughts can persist over long durations. However, the projected frequency of droughts at longer durations is low compared with droughts with shorter duration of persistence. Water resource regions (WWRs) mostly show negative change in drought characteristics, except for drought covariance. However, intensity and duration of droughts also generally increase over most of the WRRs in England, which are already highly exploited. Of particular relevance to water management, results from this ensemble have a strong influence on dry season water availability, especially in parts of England. © 2012 Springer Science+Business Media Dordrecht.