ABSTRACT
ABSTRACT: Water distribution system design is usually concerned with choosing an economical system that can satisfy a few conservative demand scenarios (e.g., greater of peak-hour or peakday + fire at the end of the design life) and still provide residual pressures above an acceptable level. The presumption is that conservatism in design will prevent most if not all hydraulic failures in a system. Despite this, a number of unusual loads can “coalesce” unexpectedly in real systems and cause them to fail sometimes dramatically and sometimes not. In this regard, a multiobjective model is formulated in this paper that balances the long-standing concerns of cost with the objectives of hydraulic reliability and water quality vulnerability. Unlike most optimization models in which demands are set to their end-of-life levels, the proposed multiobjective framework assumes that demand loads vary randomly throughout the design life of a system. A tentative vulnerability index is developed to quantify the socio-economic damages incurred in a system that experiences a water quality failure. The multiobjective framework points to the constant trade-off that an engineer must make between the objectives of cost, hydraulic and water quality performance in design.
