A weather-type approach to analysing water resource drought in the Yorkshire region from 1881 to 1998

Water resource droughts in the UK have occurred with regularity over the last 20 years. In Yorkshire, the most severe of these was from 1995 to 1996, with a return period estimate of over 200 years. `Severe' drought events since 1881 in the Yorkshire region are classified using two drought severity indices based on 3- and 6-monthly cumulative precipitation anomalies. Atmospheric circulation contrasts associated with the droughts are analysed and a methodology developed to identify water resource droughts in Yorkshire using historical weather-type information rather than precipitation data. Using a weather-type index to extend drought series and revise estimates of drought return periods is a potentially useful technique. The methodology is applied from 1881 to 1998 and highlights a large number of severe drought events between 1884 and 1896 which can be substantiated using anecdotal evidence. However, the drought events of the 1880s and 1890s have not generally been used when calculating return periods for recent drought events due to scarcity of long-term daily precipitation data. The validity of return period estimates of recent drought events must therefore be questioned. This research confirms the need for the reassessment of return period estimates for contemporary drought events particularly given current climatic trends, the rapid onset of recent droughts and rising water demands. (C) 2002 Elsevier Science B.V. All rights reserved.