Long‐term planning methodology for water distribution system rehabilitation

Abstract

Abstract. The most expensive component of a water supply system is the distribution network. Deterioration due to aging and stress causes increased operation and maintenance costs, water losses, reduction in the quality of service, and reduction in the quality of water supplied. In this paper an approach is proposed in which the water distribution network economics and hydraulic capacity are analyzed simultaneously over a predefined analysis period while the deterioration over time of both the structural integrity and the hydraulic capacity of every pipe in the system is explicitly considered. The cost associated with each pipe in the network is calculated as the present value of an infinite stream of costs. In Kleiner et al. [this issue] a methodology is presented to implement this approach into a decision support system that facilitates the identification of an optimal rehabilitation strategy. IntroductionThe most expensive component of a water supply system is the distribution network. Aging water supply infrastructure, coupled with the continuous stress placed on pipes by operational and environmental conditions, has led to system deterioration which manifests itself in increased operation and maintenance costs, water losses, reduction in the quality of service, and reduction in the quality of water supplied. Given the reality of scarce capital resources, it is imperative that a comprehensive methodology be developed to assist planners and decision makers in selecting the most cost-effective rehabilitation policy that addresses the issues of safety, reliability, quality, and efficiency. [1988] proposed an alternative to the Woodburn et al. model in which some parameters are considered as random variables and the resulting probabilistic form is then converted to a deterministic form using a chance-constrained programming approach. The problem is then decomposed into a master problem which enumerates combinations of rehabilitated/replaced/intact pipes and a subproblem which uses a nonlinear programming solver 2039

On simulation of maintenance costs for water distribution system with fuzzy parameters

“…Contrary to the previous paper, in [12], let's say, a "macro-management" approach for a WDS rehabilitation problem with a real long-time horizon is widely discussed. In this paper, both an economics and hydraulic capacity of a WDS is analysed, if a deterioration of a pipe follows the Hazen-Williams equation.…”

“…A method of a linear regression is used to model a dependency between various types of the costs (like an equipment cost) and the mentioned characteristics of a pipe (like a nominal diameter) based on data from several Portuguese urban water utilities. However, a method for a calculation of a present value of the total costs is not developed there in a more detailed way.Contrary to the previous paper, in [12], let's say, a "macro-management" approach for a WDS rehabilitation problem with a real long-time horizon is widely discussed. In this paper, both an economics and hydraulic capacity of a WDS is analysed, if a deterioration of a pipe follows the Hazen-Williams equation.…”

Optimization of maintenance costs of a pipeline for a V-shaped hazard rate of malfunction intensities

“…Such a time interval covers 20, 50 or even 60 years (see, e.g., [12]). Of course, one unit of money, which is paid now, and the same unit in 50-60 years, are not equal.…”

“…Firstly, let us mention reviews of various methods, approaches and literature, which can be found in, e.g., [15,28,29]. The papers themselves are very varied -some of them concern hydraulic and physical characteristics of parts of a WDS (see, e.g., [4,17]), other discuss rather a "macro-management" of a WDS rehabilitation problem (see, e.g., [12,22]) or only a "micromanagement" scale (e.g., for a single building, see [1]). Even some monitoring systems for failures detection in a WDS are proposed (see, e.g., [23]).…”

“…Moreover, some model for intensities of malfunctions of parts of a WDS has to be assumed. As it is proposed in literature, it can be based on selected physical aspects of a pipe and numerical equations (like the Hazen-Williams equation, see, e.g., [12]), it can be described with some type of Markov or semi-Markov process (see, e.g., [13,16,26]) or malfunctions are randomly generated using a hazard rate function (HRF). A sciENcE aNd tEchNology multilateral review of various HRFs can be found in [29].…”