This benchmark water system has been set up by the Centre for Water Systems of Exeter University as a realistic challenging problem. The aim is to determine the most economically effective design to reinforce the existing system to meet projected demands as a network. The network serves a population of approximately 400,000. It consists of relatively small pipes and few transmission mains, with a large head-loss range at the extremities of the system, making it highly sensitive to demand increases.

In order to continue to provide water to customers at the highest level, a reinforcement scheme for the network using demands projected to the year 2020 is considered to avoid low pressure problems in the future. This expansion plan is based on a calibrated model of the network with a minimum pressure requirement of 20.0m at demand nodes. The following table summarizes available discrete pipe diameters and their corresponding Colebrook-White friction factors. The unit costs for pipe laying which are function of pipe diameter and type of roads, in major roads excavations are more difficult to undertake and consequently more expensive, are given in table.

Pipe Rehabilitation Alternative Costs

Diameter (mm)
Friction Factors
Unit cost ($/m)
Minor Road/FootpathMajor Road
110 0.03 85 100
159 0.065 95 120
200 0.1 115 140
250 0.13 150 190
300 0.17 200 240
400 0.23 250 290
500 0.3 310 340
600 0.35 370 410
750 0.43 450 500
900 0.5 580 625

The full information regarding the network and the optimization problem is available from following two papers.

  1. Farmani R., Savic D.A. and Walters G.A. (2004) Evolutionary Multi-Objective Optimization in Water Distribution Network Design, Engineering Optimization, submitted for publication.
  2. Farmani R., Savic D.A. and Walters G.A. (2004) "EXNET" Benchmark Problem for Multi-Objective Optimization of Large Water Systems. Modelling and Control for Participatory Planning and Managing Water Systems, IFAC workshop, Venice, Italy, 29 Sept.- 1 Oct., 2004

The input file  of the network is available in EPANET network solver format.


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