Adaptation planning under climate change uncertainty

This project explores the uncertainty factors in drought planning for a water resource zone in Sussex. Nine planning options from the 2009 Sussex Water Resource Management Plan were assessed using four climate products: the 2009 UK Climate Projections Change Factors, the Spatial Coherent Projections, the 11 runs of the HadRM3 regional climate model and their subsequent downscaling by the Future Flows Project. The varying drought statistics from these four climate products reflect post-processing uncertainty - the uncertainty stemming from the process of converting original climate model outputs into products of different formats, variables and temporal/spatial scales. Overall, the study has integrated a cascade analysis of climate uncertainty, climate post-processing uncertainty, hydrological uncertainty, water resource model uncertainty and demand uncertainty on water resource planning. The study combines Robust Optimisation, Decision-Scaling and Robust Decision Making into Robust Decision Analysis, a decision making framework for dynamic adaptation pathways in response to different levels of uncertainty and risk averseness. Post-processing uncertainty is the dominate uncertainty until 2030s; 2050s is then dominated by demand and socio-economic uncertainty. The most severe droughts within the Spatial Coherent Projections and the 2009 UK Climate Projection products are variations of the 1975-1976 and the 1988-1989 droughts, two of the worst historic droughts currently used as the design events for drought planning in Sussex. The system appears to be robust to variations of these past droughts. Yet, under different sequences of droughts from the HadRM3 and Future Flows products, the system demonstrated frequent supply failures in the 2050s, unless water demand is maintained at the 2007 level or lower. While operational costs in the 2030s are generally within the region of 4 to 5 million GBP per year, those in the 2050s Market Forces jumped to the region of 5 to 15 million GBP per year and with supply deficit from 0 to 1100 Ml/year. When demand grows by 35% from the 2007 baseline level, universal metering becomes a key option. Despite climate post-processing uncertainty, the main hotspots of water deficits remains similar across the climate products and are driven by network bottlenecks and the continually high dependence of the system on water sources a round the Hardham area. The study also indicates that inter-regional transfers might not be as reliable as assumed.