4 - Reliability-related criteria in water supply system studies

Summary

ABSTRACT In the study of water supply system expansion in two areas of Poland, the design of a number of water storage reservoirs is considered. The reliability studies reported are based on a system simulation performed for a historical time series of observations of river flows, with and without the hypothetical reservoirs, for future water demands given in two variants. Periods of non-satisfactory and of satisfactory system performance and values of maximum and of cumulative deficits are analyzed. Frequency, duration and severity of nonsatisfactory system performance are assessed as reliability, resilience, and vulnerability. Assumption of exponential distribution of periods of non-satisfactory and satisfactory performance allows straightforward links between several criteria to be established.

INTRODUCTION

In order to evaluate various aspects of non-satisfactory performance of a technical, or natural system, it is necessary to use multiple performance criteria. The use of a set of criteria to describe the possible variants, scenarios and policies offers a perspective that cannot be achieved with a single objective.

The criteria of concern pertain to time-related characteristics (duration and frequency) of the non-satisfactory system performance and also to the amplitude-related characteristics (maximum instantaneous entry into the state of nonsatisfactory performance and the cumulated entry). The ultimate criteria, combining both above types of characteristics measure various aspects of severity and consequences of the non-satisfactory performance.