Use of UKCP09 products for the project ‘Future flows and groundwater levels’

This document describes the rationale behind the use of UKCP09 products within the future flows and groundwater projects. To ensure spatial consistency of the results and the generation of multi-decadal time series across Great Britain, the HadRM3-PPE daily time series are to be used to derive both national maps of changes in river flows statistics and daily time series of river flow and groundwater levels. Those transient river flow and groundwater level time series will enable investigating the evolution of the time series over time without having to interpolate linearly between fixed time periods and will provide multiple realisations of historic climate and flows, hence allowing a better understanding of climate variability and its impact. In addition, the changes in river flows and groundwater levels obtained from the time series will be put into the context of fuller climate change uncertainty as described by the UKCP09 probabilistic projections for a selected number of sites. To ensure data input are realistic as both fine spatial scale (typically 1-km) and temporal scale (daily), a downscaling incorporating bias correction is recommended for both precipitation and temporal time series. Snow-melt and evaporation processes are also accounted for using HadRM3-PPE climate information.