No abstract

Calibration is a process of comparing model results with field data and making the appropriate adjustments so that both results agree. Calibration methods can involve formal optimization methods or manual methods in which the modeler informally examines alternative model parameters. The development of a calibration framework typically involves the following: (1) definition of the model variables, coefficients, and equations; (2) selection of an objective function to measure the quality of the calibration; (3) selection of the set of data to be used for the calibration process; and (4) selection of an optimization/manual scheme for altering the coefficient values in the direction of reducing the objective function. Hydraulic calibration usually involves the modification of system demands, fine-tuning the roughness values of pipes, altering pump operation characteristics, and adjusting other model attributes that affect simulation results, in particular those that have significant uncertainty associated with their values. From the previous steps, it is clear that model calibration is neither unique nor a straightforward technical task. The success of a calibration process depends on the modeler's experience and intuition, as well as on the mathematical model and procedures adopted for the calibration process. This paper provides a summary of the Battle of the Water Calibration Networks (BWCN), the goal of which was to objectively compare the solutions of different approaches to the calibration of water distribution systems through application to a real water distribution system. Fourteen teams from academia, water utilities, and private consultants participated. The BWCN outcomes were presented and assessed at the 12th Water Distribution Systems Analysis conference in Tucson, Arizona, in September 2010. This manuscript summarizes the BWCN exercise and suggests future research directions for the calibration of water distribution systems.

The application of the analytic hierarchy process (AHP) to help select the best option for the long-term design and upgrading of a water distribution network is described and applied to a real-world network. The main criteria used are: reliability-based network performance; present value of construction, upgrading, failure, and repair costs; and social and environmental issues. The AHP is a versatile and robust tool that can handle both qualitative and quantitative data, based on a simple method of pair-wise comparisons. It has been applied elsewhere on various problems, but not on the long-term design and upgrading of water distribution networks. Herein, the pipes are sized to carry maximum entropy flows using linear programming, while the best upgrading sequence is identified using dynamic programming. The upgrading options considered include pipe replacement and/or paralleling. The time-dependent deterioration of the hydraulic capacity and structural integrity are also accounted for

Given a limited budget, the choice of the best water distribution network upgrading strategy is a complex optimization problem. A model for the optimal long-term design and upgrading of new and existing water distribution networks is presented. A key strength of the methodology is the use of maximum entropy flows, which reduces the size of the problem and enables the application of linear programming for pipe size optimization. It also ensures the reliability level is high. The capital and maintenance costs and hydraulic performance are considered simultaneously for a predefined design horizon. The timing of upgrading over the entire planning horizon is obtained by dynamic programming. The deterioration over time of the structural integrity and hydraulic capacity of every pipe are explicitly considered. The upgrading options considered include pipe paralleling and replacement. The effectiveness of the model is demonstrated using the water supply network of Wobulenzi town in Uganda

The application of the analytic hierarchy process (AHP) to help select the best option for the long-term design and capacity expansion of a water distribution network is described and applied to a sample network. The main criteria used are: reliability-based network performance; present value of construction, upgrading, failure and repair costs; and social and environmental issues. The AHP has been applied elsewhere on various problems, but not on the long-term upgrading of water distribution networks as proposed in this paper. The pipes are sized to carry maximum entropy flows using linear programming while the best upgrading sequence is identified using dynamic programming. The example demonstrates the effectiveness of the AHP as a systematic tool for assessing pareto-optimal designs based on the trade-offs between multiple criteria. The results demonstrate that the cheapest option is not necessarily the best when other factors e.g. performance and socio-environmental concerns are considered in an explicit way.