Evaluation and visualisation of risk to water resources

Abstract

A traditional difficulty encountered in water resource planning is the inherent uncertainty in demand and supply capability. Over recent years this uncertainty has increased for the UK water industry, owing for example to forecasts of climate change and impending directives from Europe, and in the face of such uncertainty it is no longer justifiable to design water resource systems in a deterministic fashion. Design objectives should be risk-based, and it is likely that both investors and regulators will soon request formal risk evaluation prior to major investment or strategic decisions. Consequently, there is a need for probabilistic, or risk-based, approaches to water resource assessment. A methodology for evaluation and visualisation of risk to security of water resources is presented, based on hydrological frequency of occurrence and uncertainty-based analysis of headroom (that is, the difference between supply capability and demand). The methodology makes it possible to calculate and visualise the probability of system failure for particular hydrological conditions or the probability of system failure in an arbitrary year, and to make preventive planning or operational decisions. The proposed approach is illustrated with a case study.