Real-World Considerations in Water Distribution System Design

Abstract

Engineering schools generally do a very good job teaching the fundamentals of water distribution system design. However, there are a good number of practical considerations in system design that seem to be ignored in the research literature. This paper attempts to present some important considerations in system design that are important but generally are overlooked in many research papers. Some of the considerations that are described in this paper include the types of water system planning; sources of funding and their effects; dealing with uncertainty, especially in demand forecasts; construction sequencing; and other issues that must be considered in design. The paper focuses on practices common to the United States but most of the content should be relevant in other locations. System design is driven by the need to reliably provide adequate water to customers at adequate pressure and quality while maintaining water rates (customer prices) at a reasonable level. In the early days of centralized water systems, this involved tedious manual calculations and conservative designs. As computer technology advanced, hydraulic analysis models relieved engineers from tedious calculations and enabled them to consider much more detail and perform more analyses to arrive at generally better designs. Researchers have prepared hundreds of papers on application of optimization of water system design, mostly focusing on pipe sizing. While these papers can provide some insights to practicing engineers, real-world details often need to be neglected to force the real problem to acquiesce to the optimization formulation, which usually involves minimizing some objective function(s) subject to some constraints. Hopefully, this paper can point out some considerations that need to be accounted for in any analysis of water system design. Each consideration is described with its implications in the following sections.