Iterative Methodology of Pressure-Dependent Demand Based on EPANET for Pressure-Deficient Water Distribution Analysis

Traditional water distribution simulations, known as demand-driven analysis (DDA), are normally analyzed under the assumption that nodal demands are known and satisfied. The DDA is valid under normal conditions and in design requirement. However, in situations such as pipe burst or pump outage, the outflows at nodes affected by low pressures will decrease. Therefore, network simulation under deficient pressure conditions using conventional DDA can cause large deviation from actual situations. The purpose of this paper is to analyze different compositions of nodal outflow, including volume-driven demand, pressure-dependent demand and leakage to simulate deficient network performance more realistically. An extension of the modeling package EPANET, which implements repetitive modifications to nodal outflows based on pressure-dependent demand formulations and leakage models (EPANET-MNO), is first developed. Then, a comparison is made between the respective performances of four different pressure-dependent demand functions with the designated required pressure and minimum service pressure. The EPANET-MNO was verified in two abnormal situations, including fire flow and pipe failure isolation in steady simulation. Finally, pipe failure isolation in extended period simulation was carried out on a real network. This paper demonstrates that good modeling performance and convergence of the EPANET-MNO can be achieved for simulating deficient-networks considering volume-driven demand, pressure-dependent demand and leakage.