THE PUBLISHING HOUSE PROCEEDINGS OF THE ROMANIAN ACADEMY, Series A, OF THE ROMANIAN ACADEMY Volume 11, Number 4/2010, pp. 330–339 OPTIMIZATION OF WATER DISTRIBUTION NETWORKS Ioan SÂRψU “Politehnica” University of Timisoara, Piaţa ψisericii, no. 4A, 300233 Timişoara E-mail: ioan.sarbu@ct.upt.ro The paper approaches the optimization of water distribution networks supplied from one or more node sources, according to demand variation. Traditionally, in pipe optimization, the objective func- tion is always focused on the cost criteria of network components. In this study an improved linear model is developed, which has the advantage of using not only cost criteria, but also energy con- sumption, consumption of scarce resources, operating expenses etc. The paper treats looped networks wich have concentrated outflows or uniform outflow along the length of each pipe. An improved model is developed for optimal desing of new or partially extended water distribution networks, which operate either by means of gravity or a pump system.The model is based on the method of linear programming and allows the determination of an optimal distribution of commercial diameters for each pipe in the network and the length of the pipes which correspond to these diameters. Also, it is possible to take into account the various functional situations characteristic found during operation. This paper compares linear optimization model to the some others, such as the classic model of average economical velocities and Moshnin optimization model. This shows the good performance of the new model. For different analyzed networks, the saving of electrical energy, due to diminishing pressure losses and operation costs when applying the developed model, represents about 10…3η %. Key words: Water supply, Distribution, Looped networks, τptimal design, Linear optimization model. 1. INTRODUCTION Distribution networks are an essential part of all water supply systems. The reliability of supply is much greater in the case of looped networks. Distribution system costs within any water supply scheme may be equal to or greater than θ0 % of the entire cost of the project. Also, the energy consumed in a distribution network supplied by pumping may exceed θ0 % of the total energy consumption of the system. Attempts should be made to reduce the cost and energy consumption of the distribution system through optimization in analysis and design. A water distribution network that includes bosster pumps mounted in the pipes, pressure reducing valves, and check-valves can be analyzed by several common methods such as Hardy-ωross, linear theory, and σewton-Raphson [20]. Traditionally, pipe diameters are chosen according to the average economical velocities (Hardy-ωross method) [η]. This procedure is cumbersome, uneconomical, and requires trials, seldom leading to an eco- nomical and technical optimum. This paper develops a linear model for optimal design of new and partially extended distribution sys- tems supplied by pumping or gravitation. It is based on linear programming and allows for the determi- nation of optimal distribution of commercial diameters along the length of each pipe and the length of pipe sectors corresponding to these diameters. It is possible to take into account various functional situations characteristic found during operation and uniform outflows along the length of each pipe. This model can serve as guidelines to supplement existing procedures of network design. 2. BASIS OF HYDRAULIC CALCULATION A distribution network may be represented by orientation comprising a finite number of arcs (pipes, pumps, fittings) and a set of nodes as well as reservoirs and pumps or pipe intersections.