Pressure-Based Modeling for Reclaimed Water Systems

A pressure-driven analysis has been developed to model residential irrigation systems. This approach models each sprinkler as an orifice with a free discharge. An individual sprinkler with supply piping is represented by a characteristic P-value. An equivalent characteristic P-value is used for multiple sprinklers with their supply piping in an individual residential landscape and an overall equivalent characteristic P-value for a junction in a distribution main to multiple residential landscapes. The pressure-flow relationship at a demand node is presented by means of hydraulically-aggregated junctions in the distribution main with a rotation factor for simultaneous operations. A general design methodology is summarized in the paper. The pressure-driven analysis has been successfully used in the City of Rockledge's reuse water system for on-demand flow forecasting. In comparison with test data, the analysis could predict the actual flow within 0.3% and 5.6% margins for two remote subdivisions. The predicted flows by demand-driven analysis were not in agreement with the measured flows.