State estimation (SE) techniques are being applied to different network systems in order to convert system measurements into real information about the network state. SE applications to water systems are relatively novel, but these techniques have been implemented in other fields for decades. In those applications, observability analysis (OA) is required prior to application of SE techniques with different purposes: (1) to identify redundant information, (2) to detect elements that make no contribution in the subsequent SE process, or (3) to identify observable islands. However, no discussion has been found in the pertinent literature regarding any interest in applying OA to water networks, with there being only a few basic applications. The aim of this paper is twofold: first, to present the implementation of a novel algebraic OA approach to water networks, which is based on the application of a Gauss elimination technique to the measurement Jacobian matrix, and to discuss and justify the interesting aspects of implementing an OA in water transport networks (WTN) prior to using SE while also presenting the issues that this technique may resolve. The results obtained highlight the algorithm potential for real supply systems, improving the knowledge of what information provided by supervisory control and data acquisition (SCADA) systems is really worth compiling.

In this paper, an alternative uncertainty treatment for the traditional unconstrained weighted-least-squares (WLS) method is presented. This treatment enables hydraulic constraints (i.e., null demands at transit nodes or null flows at closed pipes, pumps, or valves, etc.), high-precision measurements, and upper and lower variable bounds (i.e., head levels at tanks) to be included within the state estimation (SE) problem for water distribution systems. With this approach, there is no need to choose appropriate weights associated with these types of measurements in order to correctly assess uncertainty for the SE problem. The method set out herein tackles these as constraints and works with the linear system of equations derived from imposing first-order optimality conditions for the constrained SE problem. This approach enables general quantification of the SE uncertainty for all the hydraulic variables within the water system by applying the first-order second-moment (FOSM) method. Moreover, it en...

State estimation (SE) techniques can be applied to compute the most likely hydraulic state of a water distribution system from the available measurements at a given time. Different approaches exist in the technical literature to undertake such an analysis, but in all of them it is assumed that pump and valve statuses are known beforehand. Such consideration may lead to unrealistic results if real-time unnotified changes in the operation of the network take place, limiting the usefulness of the information provided by telemetry systems. This work eliminates the known-status assumption and presents the concept of topological state estimation (TSE), which not only computes the hydraulic state of the system, but also the current pump and valve status according to the existing measurements. More specifically, a novel methodology for TSE is set out in this paper. The proposed method is derived from the original mixed-integer non-linear programming formulation of the problem, which is transformed in an iterative mixed-integer quadratic programming problem by linearizing some hydraulic constraints. The potential of the methodology is presented by means of an illustrative example and a large case study, in which pumps, gate valves and check valves exist. Results show that TSE would successfully contribute to make the most of available telemetry systems, hence expanding the online monitoring possibilities of water distribution networks.

The aim of observability analysis (OA) is to determine if a given measurement setting is sufficient to compute the current status of a water distribution network. There are several approaches in the technical literature for making such an analysis. With all of them, there is an assumption that the lie of the land of the network in terms of the status of its pumps and/or valves is known. This paper omits this assumption and introduces the concept of topological observability analysis (TOA), which aims to determine not only if it would be possible to compute the hydraulic state of a network from the available measurement set (ordinary OA), but also if the status of pumps and valves would be observable as well. Additionally, a method is proposed that modifies the standard measurement Jacobian matrix by incorporating either equations and/or unknowns depending on the available information for each specific pump or valve. The rest of the analysis can be undertaken using any of the existing methods for OA in the literature. An illustrative example is presented by way of illustration to show the potential of TOA, which would certainly enhance online monitoring systems.