Using seasonal forecasts to inform the management of water resources during drought.

Water is considered to be one of the main mechanisms through which people will experience climate change, with the number of people estimated to become exposed to water scarcity projected to increase sharply in the future. Water resource managers in the UK have access to a range of meteorological and hydrological indicators of drought. However these data are limited in their utility to directly forecast how systems should be managed to reduce impacts on water users. At present there is no generically applicable method to provide such an outlook.

We are working with practitioners and regulators in the UK water industry to demonstrate the use of seasonal forecasts to support decision-making during drought. The work is funded by Copernicus through the European Centre for Medium-Range Weather Forecasts (ECMWF) with the aim of showing how Copernicus Climate Change Service (C3S) data can be used in sectoral contexts. C3S data are combined with both operational practices and the latest UK water resources planning developments to provide metrics of value tailored to the needs of water resource managers. National and industry stakeholders have been fully engaged from the outset, co-creating a tool to evaluate, visualise, and communicate the potential impact of emerging droughts in a meaningful way.

The tool reads water supply system information presented by water companies including drought response surfaces, operational decisions, and demand. The water supply system is simulated using seasonal forecasts, and an assessment of drought likelihood and vulnerability is provided along with an estimate of the associated uncertainty. Impacts are presented in terms of consequences for stakeholders and contextualised in terms of system vulnerabilities and the historic record. This tool supports operational decision-making, in particular when deliberating the timing of supply and demand-side interventions as a drought develops, and communicating such risks to stakeholders.