Operational Water Distribution System Research Articles

Assessing Ground Support of Plastic Pipes Using Ultrasound

The ability to detect early signs of failure in buried pipe infrastructure is necessary to facilitate the continued use of ageing infrastructure for delivery of society’s essential services and move beyond disruptive and expensive reactive maintenance and repair. This paper reports detailed experiments on the use of in-pipe ultrasound techniques for assessment of ground conditions around buried plastic pipes. Two sets of ultrasonic experiment on the soil conditions are presented: (1) existence, shape, and dimension of void, and (2) water content in the soil. The ultrasound technique is shown to be capable for detecting water filled voids and assessing the soil support, critical early indicators of failure. The technique requires water as the transmission media hence is naturally suited to application in operational water distribution systems. The work represents an important advance in in-pipe condition assessment of plastic pipes, demonstrates the practical capability of the ultrasound technique, which is critical for progression towards proactive maintenance, offering cost and service improvements.

Numerical investigation of the impact of irregular pipe wall build-up on velocity in the water distribution system

AbstractThis paper presents novel equations for different wall build-up types in old pipes developed for the estimation of real flow velocities in a water distribution system (WDS). This is important when estimating the contamination propagation rate in an operational WDS. Because the inner surface geometry of old rough pipes is complex, real velocities cannot be estimated by conventional WDS models. Therefore, a computational fluid dynamics (CFD) model was used to analyse the flow dynamics in old rough pipes with even and uneven roughness build-up. The developed equations for the velocity correction coefficients derive from the results of numerical simulations. Numerically obtained velocity fields show that in some cases, pipe wall build-up can affect the effective flow section significantly and the flow velocity can be underestimated by more than two times. Therefore, different velocity correction equations have to be used for different types of pipe wall build-up.

A modeling framework for critical infrastructure and its application in detecting cyber-attacks on a water distribution system

Critical infrastructure (CI), such as systems for water treatment, water distribution, power generation and distribution, is vital for the well being of a society. Such systems are typically large, complex, and interconnected. A cyber-attack on one such system could affect the other. In this work, a generic agent-based framework is proposed to aid in modeling a CI. Combined with a proposed methodology, the framework can be used to model a CI, and those connected to it, as an aid to understanding their collective behavior when subjected to cyber attacks. In a case study, the proposed framework was used to create a model of an operational water distribution system and validated experimentally using a set of cyber attacks launched against an implementation of the model.

Awa: Using water distribution systems to transmit data

AbstractThis article presents Awa, a real‐time wireless monitoring solution for urban water distribution systems (WDSs). The Awa system is composed of a distributed network of low‐cost sensor nodes that can be quickly installed on water pipes. Rather than using conventional radio signals, which are attenuated in underground environments, the nodes use the actual water‐filled pipe as the transmission medium to communicate with one another. This permits the use of an already existing water infrastructure in the deployment of large wireless sensor networks. We describe the development and evaluation of novel and battery‐powered sensor nodes that can be magnetically clipped to valves and hard‐to‐access points in WDSs without requiring digging or cutting of pipes. A channel characterization is carried out and a number of data modulation schemes are evaluated across a 110‐m section of pipe in an operational WDSs. We identify a near‐optimal frequency (near 500 Hz) for transmitting data. We demonstrate communication at 100 bps across a real‐world water pipe using amplitude modulation. Not unlike radio‐frequency wireless, we also measure the highly nonstationary effects of multipath fading. The article also contains an in‐depth discussion about the opportunities that this emerging communication technology offers in the context of city‐wide leak detection and flow monitoring.

Real-time demands and calibration of water distribution systems

All computer models of water distribution systems (WDS) have to contain information about demands. Usually demands are derived based on customer's water meters weekly or monthly readings. It gives information only about the average demand. Dynamics of hourly, daily and weekly demands are usually estimated based on typical demand patterns of different type of consumer groups like domestic households, hospitals or hotels. Estimation of demand dynamics by this manner inevitably decreases precision of calibration. Calculations show that differences between real-time and typical demand can influence results of calibration. The paper proposes some methods to minimize this influence. Special software has been developed for estimation of real-time water demands in a WDS. Algorithms and software checked on an operational WDS.

Occurrence of Transients in Water Distribution Networks

The common existence of pressure transients in operational water distribution systems (WDS) requires their characterisation and assessment of their impact. This paper performs such characterisation by evidencing the occurrence and the differences in pressure transient behaviour in complex WDS. Ten samples of continuously recorded high resolution pressures from diverse networks and sources were analysed. The presented pressure traces show regular and occasional pressure transient waves in various complex networks. Histogram analysis of the rate of change of head provides some insight into transient behaviour in these sites. Although there was no distinct correlation between network characteristics (ie. length, diameter, age) and transient behaviour, network complexity was observed to change the transient characteristics. Transient characteristics were observed to be strongly influenced by likely sources, in particular commercial customers. The data highlights the need to understand, quantify and characterise transients and hence link to possible impacts, such as structural or water quality failures.

Different Approaches for Calibration of an Operational Water Distribution System Containing Old Pipes

Model of a water distribution system (WDS), containing old pipes, requires calibration to estimate the roughness of old pipes. Pipe roughness increases with age. In some cases the estimated roughness of old pipes, using optimization procedures based on measurements in operational WDS, can be quite high. Therefore it would be proper to use real diameters of the old pipes instead of high roughness values. The aim of the paper is to compare different approaches of calibration in such case. Five different calibration methods are analysed changing pipe roughness, diameter or both. Calculations have been conducted for an operational WDS. Measurements in the WDS indicated that there are quite large differences in the dynamics of demands (even for the same customer categories) in different zones of the system. It is shown that this has strong influence on the calibration results.

Estimation of real-time water fluxes in water distribution system on the basis of pressure measurements

Experience in calibration of water distribution system (WDS) models shows large uncertainties of demands estimated on the basis of typical hourly values for different types of consumers. The typical dynamics of demands, which are used for the lack of more detailed information, differ from real-time demands in time and in space. It makes it difficult to estimate real-time water fluxes in WDS which are necessary for evaluation of the propagation rate of the contaminated zones in case of deliberate or accidental chemical or biological threats. The aim of this investigation was to test the possibility of estimating real-time water flow fluxes in District Meter Areas (DMAs) on the basis of pressure measurements. Results have been tested on the operational WDS.

Calibration of a model of an operational water distribution system containing pipes of different age

The aim of the paper is to demonstrate that the Levenberg–Marquardt algorithm can give successful results when operational water distribution systems are calibrated with the proper selection of parameter increment for the calculation of partial derivatives. The functional dependence of pipe roughness on age, which describes linear and nonlinear dependences, is proposed for the calibration of a model of a water distribution system containing pipes of different age. It is also shown that the visualization of response surface on a coarse grid is very useful for the analysis of the results.