Design, Expansion and rehabilitation of water distribution networks aimed at reducing water losses. Where are we?

This paper aims at presenting the historical evolution and the present status of water distribution network design approaches in the light of water losses reduction. Although pressure management has been recognised as one of the four actions aimed at reducing water losses, very little work is currently available in the literature on design criteria that would allow improving pressure management in operation. Only recent works have aimed at improving design of new systems or expansions and rehabilitation of the existing networks by formulating a multi objective problem, where the first objective is clearly the reduction of costs (network, non revenue water, maintenance), while additional objectives, aim at improving resilience of the system by reducing the internally dissipated power and at re-distributing more evenly the pressure field over the entire water distribution network. The new techniques have the advantage of producing networks that can be operated under lower pressure fields, which is the objective of pressure management. The new multi objective optimization techniques are generally based on genetic algorithms, which make extensive use of network analysis and simulation. Therefore the paper also discusses the representation of leakage losses in the current generation of water distribution networks simulation packages. The presently available approaches are shown to be unsatisfactory in that they produce considerable errors in terms of energy and head losses. The paper concludes by presenting a set of possible alternatives and future perspectives.