Network Flow Analysis under Water Shortage andDecompressed Water Supply Control

This paper describes a method of a network flow analysis under water shortage and water distribution control with reduced pressure. As a water shortage measures, the water supply pressure should be kept at lower level than usual to save water. In this status the control of pumps and valves are difficult because the demand varies according to the pressure. In a conventional method of the analysis the pressure at the water supply bases and the demand distribution on the pipeline network are given. Then, the entire pressure and flow distribution can be obtained by solving the equations of the pressure equilibrium and the flow quantity preservation. When the pressure is not sufficient, the demand at the node is the function of the supply pressure and the usual method does not apply.

We enhance the conventional network flow analysis by introducing the relation between the supply pressure and the volume of water taken out of the node. A control method based on this analysis is proposed with which the pumps and the valves are controlled correctly. A simulation using actual data shows that adequate operation can keep the water saving target while maintaining uniform pressure distribution as possible.