Drought Characterisation and the Application of Indices in UK Water Resource Management

Abstract:

Drought is a complex phenomenon, occurring in most climatic zones, including both high and low rainfall regions. Recent drought events (2004-2006 & 2010-2012) in the UK have highlighted a continued vulnerability to this hazard. The period 2010-2012 was characterised by departures from typical seasonal climatic conditions, resulting in a severe drought, which had a significant impact on water resources in parts of the UK. Recent droughts highlight the need for better understanding of extreme drought events, particularly from a water resource perspective. The UK has a wealth of long climate series that are under used for water resource management planning. Standardised drought indicators offer a potential monitoring and management tool for operational water resource management. However, the application of these metrics for operational water resource management needs further investigation, particularly links between meteorological drought indices, streamflow, groundwater and water supply systems.

This work uses standardised drought indices (Standardised Precipitation Index and Standardised Precipitation Evaporation Index) to characterise drought from 1858-2013 within a 21,000 km² water supply region serving 7.4 million people. Meteorological drought characterisation highlights the severity of late 19^th Century droughts (1887-1889, 1890-1910) which are rarely considered in water resource modelling and drought management planning; current UK water resource modelling typically uses data from 1920-2012. Drought characterisation is used to extend the water resources modelling period back to 1884, permitting investigation of the impacts of pre-1920s droughts on reservoir yields and exploring how meteorological and hydrological drought characteristics impact the water supply system. Drought characteristics are also used to investigate the propagation from meteorological drought to hydrological drought using observed data from rivers, aquifers and reservoirs to develop a better understanding of the links between drought indices and observed drought impacts. Exploring how meteorological drought indicators link to the water supply region helps build an understanding of their utility for water resource management.