Comparison between dynamic and steady-state models for evaluating the real and apparent water losses

In the last decades, one of the main concerns of the water system managers have been the minimisation of water losses, that frequently reach values of 30% or even 70% of the volume supplying the distribution network. The economic and social costs associated with water losses in modern water supply systems are rapidly rising to unacceptably high levels. Furthermore, the problem of the water losses assumes more and more importance mainly when periods of water scarcity occur or when not sufficient water supply takes part in areas with fast growth. In the present analysis, a dynamic model was used for estimating real and apparent losses of a real case study. A specific nodal demand model reflecting the user’s tank installation and a specific apparent losses module were implemented. The real losses were described through a general pressure dependent relationship whose parameters were calculated based on the results of field inquiries. The demand model is based on the combination of the tank continuity equation and a pressure driven demand relationship, and represents the private tank filling process, the variation of the tank inflow, depending on the network pressure, and tank water level. The apparent losses module is able to quantify by means of average meter error curves the intrinsic meter error related to the flow rate passing through the meter and the pressure at the node. The results from the dynamic model were compared with the modelling estimation based on a steady-state approach.