Optimal Design and Rehabilitation of Water Distribution Systems

Computer models are vital for the evaluation and management of hydraulic infrastructure systems. This paper describes the development of an efficient computer optimization software system, called H₂ONET Designer, for use in obtaining the least-cost design and rehabilitation of municipal water distribution piping systems. The software system links an object-oriented hydraulic network solver and an optimization model in a fully integrated graphical mapping and database management environment to provide an effective computer aided decision-support tool for water engineers. The optimization model is based on a variation of the genetic algorithm employing a global search strategy and delivering reliable solutions in sub-quadratic times. Least cost design and improvement solutions are chosen to satisfy designated performance constraints on the network hydraulics for any given range of demand loading and operating conditions. Network improvements can include cleaning, cleaning and lining, pipe expansion, and/or installing new pipes (as constant diameter pipes or split pipes of differing diameter) that can either parallel or replace existing pipes. The constraint set prescribes minimum bounds on node pressures and maximum bounds on pipe velocities and hydraulic gradients that are allowed in the system. Comparisons with published results show improved performance, rapid convergence, and applicability to large-scale water distribution systems. Enhancement of water distribution infrastructure planning and management is a principal benefit of the proposed software system.