Holistic planning methodology for long-term design and capacity expansion of water networks

The application of the analytic hierarchy process (AHP) to help select the best option for the long-term design and capacity expansion of a water distribution network is described and applied to a sample network. The main criteria used are: reliability-based network performance; present value of construction, upgrading, failure and repair costs; and social and environmental issues. The AHP has been applied elsewhere on various problems, but not on the long-term upgrading of water distribution networks as proposed in this paper. The pipes are sized to carry maximum entropy flows using linear programming while the best upgrading sequence is identified using dynamic programming. The example demonstrates the effectiveness of the AHP as a systematic tool for assessing pareto-optimal designs based on the trade-offs between multiple criteria. The results demonstrate that the cheapest option is not necessarily the best when other factors e.g. performance and socio-environmental concerns are considered in an explicit way.