Uncertainty Analysis of an Integrated Water System in Southern England: Exploring Physical and Socio-economic Uncertainties

Climate change risk assessment of water resources is fraught withuncertainty. Such uncertainty is not only the accumulation of individual uncertaintycomponents, but also the results of intricate interactions amongst the physicalenvironment and the socio-economic system. There is often a mismatch of modelrepresentation of these two systems: while uncertainty of physical factors has oftenbeen described using quantitative methods, socio-economic factors have largelybeen qualitative. In our drought assessment case study, we evaluate uncertainty inthe physical factors and demand responses in the context of climate change. Inparticular, we focus on structural uncertainty of the supply component and datauncertainty of the demand component. To explore structural uncertainty, a model offine scale that has nodes representing real supply and demand sources was usedas a reference model; another model at the water resource zone scale was usedas an emulator to reflect information loss if a coarser spatial resolution is used. Theinput data are the UK Climate Projections 2009, 1989-2011 historic demand and1961-1990 historic climate data. The main model output of interest is failure ofsupply. We found that uncertainty from the hydrological model contributes a highuncertainty margins to the final model results; in this case study it is moreinfluential than uncertainty from either projected climate change or demand growth.