Denis Gilbert

DUAL CALIBRATION FOR COUPLED FLOW AND TRANSPORT MODELS OF WATER DISTRIBUTION SYSTEMS

The operation of drinking water supply networks is generally assessed using two complementary computer models. Firstly, the flow rates in the system are predicted from a hydraulic model with given input parameters and a network graph. Then the calculated pipe velocities are used in a transport reaction solver to determine various indicators for water quality, such as residence times, source tracings, and disinfectant concentrations. High parameter uncertainties require parameter estimations to be made to improve the predictions of the two coupled models. The objective of this paper is to assess if a dual calibration for these coupled models is possible through the use of a gradient method. Based on field data measurements, such as tank levels, pressures, flow rates and chlorine concentrations, a weighted least-squares problem is defined for an over-determined system to minimize the residuals between observed and model values. A direct solution based on the Levenberg-Marquardt method is proposed. The dual calibration was tested on two real networks and was shown to be effective even with inevitable unexpected circumstances. The parameter uncertainty, or even the observability, was found to be strongly linked to measuring device placement. Selecting measuring devices that are more sensitive may drastically improve the conditioning of the calibration problem.

Accurate and Optimal Sensor Placement for Source Identification of Water Distribution Networks

AbstractThe problem of sensor placement for early-warning detection systems is a topical issue for industry and utilities who want to equip their networks with such technology. Solving the problem ...

Intentional contamination of water distribution networks: developing indicators for sensitivity and vulnerability assessments

Performing a comprehensive risk analysis is primordial to ensure a reliable and sustainable water supply. Though the general framework of risk analysis is well established, specific adaptation seems needed for systems such as water distribution networks (WDN). Understanding of vulnerabilities of WDN against deliberate contamination and consumers’ sensitivity against contaminated water use is very vital to inform decision-maker. This paper presents an innovative step-by-step methodology for developing comprehensive indicators to perform sensitivity, vulnerability and criticality analyses in case of absence of early warning system (EWS). The assessment and the aggregation of these indicators with specific fuzzy operators allow identifying the most critical points in a WDN. Intentional intrusion of contaminants at these points can potentially harm both the consumers as well as water infrastructure. The implementation of the developed methodology has been demonstrated through a case study of a French WDN unequipped with sensors.

Iterative Multistage Method for a Large Water Network Sectorization into DMAs under Multiple Design Objectives

AbstractThis paper considers the sectorization of a large water distribution network into district metered areas (DMAs) and simultaneously optimizes rehabilitation of the network with new pipes, co...