Extensive analysis of hydraulic parameters in a large set of water distribution systems

A large number of distribution network pipes in Portugal is over-sized for human demand flows, due to regulatory fire-fighting minimum diameters, which has a direct bearing on water quality, given the potentially low velocities it may originate. In order to assess the magnitude of the problem, a large scale study was undertaken, based on twenty water distribution system sectors, from networks across the country, representative of a wide range of conditions. Calibrated hydraulic models developed and updated by the utilities were provided. The extended period models were used for exhaustive runs of typical operational conditions, and the results - flow velocity, pressure, head loss and Reynolds number - were recorded for the sets of time periods concerned. The results were analyzed by using a computer application specifically developed for this purpose. A complete set of statistics for the above parameters was produced. Performance assessment of water distribution systems was also performed based on the results obtained. The main conclusions were that (i) the networks are over-designed with very low velocities in most of the time (due to being designed for the peak flow conditions in 40-year time and for fire-fighting conditions) and (ii) the systems are operated with pressures higher than necessary with evident potential of water losses and energy saving.