A System for Optimal Design of Pressure Constrained Branched Piped Water Networks

Abstract

Rural water networks in the developing world are typically branched networks with a single water source. The main design decision to be made for such networks is the choice of pipe diameters from a discrete set of commercially available pipe diameters. Larger the pipe diameters, better the service (pressure), but higher is the capital cost. In general, each link (connection between two nodes) in the network can consist of several pipe segments of differing diameters. For such networks, existing design tools solve the constrained-optimization problem heuristically [1][2]. In [3], an ILP formulation is proposed for the special case of one pipe diameter per link. This means that currently one can either get an optimal solution for the special case of one piped segment per link or get a non-optimal solution for the general case of multiple pipe segments per link. In this work, we come up with a model that solves the general formulation while still maintaining optimality. Our model has an LP formulation. It not only manages to optimally solve the general case, it also has a runtime performance that is better than both the heuristic approach to the general problem as well as the optimal approach to the specific problem (one pipe per link). To aid the designers of piped water networks, we have developed an optimization system called JalTantra that implements this model. It also has GIS functionality integrated for ease of providing network details. It is publicly available at http://www.cse.iitb.ac.in/jaltantra/.