18 - Risk and reliability in water resources management: Theory and practice

Summary

ABSTRACT

The existence of a gap between theory and practice of risk and reliability in water resources management has been widely recognized. An overview of stages of risk management is offered. It consists of: identification of failure modes; evaluation of likelihood of each failure mode; listing the consequences of each failure; risk valuation and mitigation. The results of these stages are synthesized, to form the basis for selection of an optimal plan or policy. Finally, the role of forecasting in risk management practice is reviewed.

INTRODUCTION

There is a gap between the theory and practice of incorporating considerations of risk and reliability into management of water resources systems. The reasons for this are:

1. Criteria for defining risk and quantifying reliability have not been standardized and accepted; and

2. Methodologies for incorporating reliability measures and criteria into procedures and formal models for management of water supply systems are still not well developed, and the complexity of those methods and models that do exist make them difficult to use in engineering practice.

Reliability criteria should be defined from the point of view of the consumer, and reflect the costs of less-than-perfect reliability. Here “cost” means the measurable economic losses due to failures, such as the loss of crops that are not irrigated on time or the loss of production in a factory, and any other loss incurred by failure to supply an adequate quantity of goodquality water at the time it is required. Losses are very difficult to measure and quantify, especially those associated with the quality of life of urban consumers.