Future water resource assessments to support Net Zero: hydrological projections for England incorporating both climate change and socioeconomic demands

To achieve Net Zero ambitions in England, as with other countries, there is a need to ensure security of water supply for the decarbonisation technologies that are pivotal to such aims. This requires future scenarios of water resources, particularly river flow, but to date, a majority of projections in England have focused solely on the impacts of anthropogenic warming. Future assessments of socioeconomic demand have typically been constructed separately for different sectors and have largely been estimated regionally rather than the fine scales needed for planning purposes. Hence, England has lacked readily accessible projections that integrate all of these factors to provide spatially-resolved assessments of future water resources. Indeed, internationally, there are few examples of hydrological projections that are fit-for-purpose for the challenge of quantifying future water resources for energy infrastructure alongside public supply and other demands.  

Here we describe how the CS-N0W programme (Climate Services for a Net Zero World) has delivered spatially distributed projections of future resources for England, to the 2080s, accounting for both climate change and future changes in human influences on river regimes (namely abstractions and discharges). The projections are based on the latest 12km, 12-ensemble member UKCP18 climate projections, run through the 1km Grid-to-Grid distributed hydrological model. Crucially, this version of Grid-to-Grid incorporates layers of contemporary abstractions and discharges that are perturbed into the future according to three newly co-designed demand scenarios. These demand scenarios were developed by integrating existing scenarios of future water use for the public water supply and energy sectors alongside other abstractors (e.g. industry, agriculture). We showcase the potential of the projections for analysis of future water resources, quantifying changes in drought and low flow indicators for >600 catchments as well as larger-scale water resources planning regions. Finally, we describe how the projections have been turned into accessible, actionable information for policy- and decision-makers through a mapping and visualisation portal, co-designed with a stakeholder group representing a wide range of actors involved in water management.