ABSTRACT
Pressure-driven demand (PDD) models have become essential tools for hydraulic analyses of water distribution networks under stress conditions. They are commonly based on the concept of emitter coefficients initially developed within EPANET software of US EPA (Rossman, 2000). Thanks to substantially improved computational speed in the past decade, fairly large networks can be processed by PDD models, nowadays. Nevertheless, the PDD models are still unable to simulate some specific situations appearing in reality. The research presented in this chapter assesses the PDD algorithm for calculations of networks laid in topography with extreme altitude range. The negative emitter demands resulting from high altitudes are taken as an indicator of total demand loss and are eliminated after removing the emitter and setting the node demand to zero. In addition, a situation is analysed where the loss of demand can also be dependent from altitude range preventing conveyance through non-demand nodes of extremely high elevation, which are also generating negative pressures. The approach has been demonstrated on a few simple scenarios. The results point the deficiencies of neglecting high elevated nodes without the demand and the introduction of lower PDD threshold limit for (temporary) disconnection of the pipes connected to the negative-pressure nodes.
