This paper explores numerically the benefits of water discharge prediction in the real time control (RTC) of water distribution networks (WDNs). An algorithm aimed at controlling the settings of ...control valves and variable speed pumps, as a function of pressure head signals from remote nodes in the network, is used. Two variants of the algorithm are considered, based on the measured water discharge in the device at the current time and on the prediction of this variable at the new time, respectively. As a result of the prediction, carried out using a polynomial with coefficients determined through linear regression, the RTC algorithm attempts to correct the expected deviation of the controlled pressure head from the set point, rather than the currently measured deviation. The applications concerned the numerical simulation of RTC in a WDN, in which the nodal demands are reconstructed stochastically through the bottom-up approach. The results prove that RTC benefits from the implementation of the prediction, in terms of the closeness of the controlled variable to the set point and of total variations of the device setting. The benefits are more evident when the water discharge features contained random fluctuations and large hourly variations.
Leakage represents a crucial issue in the management of water distribution networks (WDNs). Due to leakage dependence on service pressure, the application of pressure real-time control (RTC) can ...effectively alleviate the problem. Current RTC implementations rely on a closed-loop control of pressure at a single (local or remote) node of the WDN. In this case, the regulation performance may be good at the selected node, but rather poor across the whole WDN. While conservative choices are usually carried out to mitigate it, this issue becomes extremely relevant in the case of multiple nodes reaching critical values of pressure during the day. This work proposes a novel multinode (MN) RTC approach, which explicitly considers closed-loop control of pressure at multiple WDN nodes. The control scheme is based on a Kalman Filter for state and disturbance estimation, a steady-state auxiliary target calculator, and a model predictive controller for regulation and disturbance rejection. A detailed pressure-driven, unsteady flow model is used to simulate a real WDN under different demand scenarios and assess the performances of the proposed approach, which delivered satisfactory results. Moreover, the MN-RTC approach discussed in this work is suitable for in situ implementation, due to its low computational complexity. Finally, as demonstrated in the simulated environment, the tuning of the control algorithm can be performed by relying on input-output data collected directly from the plant, with no need for a hydraulic simulator.
In this paper, a simplified methodology to increase the water distribution equity in existing intermittent water distribution systems (WDSs) is presented. The methodology assumes to install valves in ...the water distribution network with the objective to re-arrange the flow circulation, thus allowing an improved water distribution among the network users. Valve installation in the WDS is based on the use of algorithms of sequential addition (SA). Two optimization schemes based on SA were developed and tested. The first one allows identifying locations of gate valves in order to maximize the global distribution equity of the network, irrespectively of the local impact of the valves on the supply level of the single nodes. Conversely, the second scheme aims to maximize the global equity of the network by optimizing both location and setting (opening degree) of control valves, to include the impact of the new flow circulation on the supply level of each node. The two optimization schemes were applied to a case study network subject to water shortage conditions. The software EPA Storm Water Management Model (SWMM) was used for the simulations in the wake of previous successful applications for the analysis of intermittent water distribution systems. Results of the application of the SA algorithms were also compared with those from the literature and obtained by the use of the multi-objective Non-Dominated Sorted Genetic Algorithm II (NSGA II). The results show the high performance of SA algorithms in identifying optimal position and settings of the valves in the WDS. The comparison pointed out that SA algorithms are able to perform similarly to NSGA II and, at the same time, to reduce significantly the computational effort associated to the optimization process.
This paper presents some developments in the optimization effectiveness for the dynamic design of water distribution networks (WDNs), tackled employing multi-objective genetic algorithms. Unlike the ...traditional single-phase design, the dynamic multi-phase design operates on planning WDN upgrades on short time intervals, also called phases or stages, while fitting them into a long-term planning horizon, thus requiring bespoke research efforts for the improvement of the optimization effectiveness. A modified version of dynamic NSGA-II optimization is introduced here, including: no penalty on the objective functions for infeasible solutions, adoption of engineering judgments in the construction of optimization individuals, restricting the number of parallel pipes at each site. This results in the improvement of convergence speed and solution quality in two case studies with different complexities.
Abstract
This paper proposes a formulation of modularity tailored to the dual water distribution network (WDN) topology based on segments and valves, to be conveniently adopted for the partitioning ...into district-metered areas (DMAs). Notably, it allows considering both properties to be made uniform across DMAs, such as water demand or total pipe length, and properties to be made uniform inside each DMA, such as nodal ground elevations or pipe age for the sake of pressure regulation or maintenance easiness, respectively. This paper also proposes a new algorithm for the identification of the optimal clustering of WDN segments into any desired number of DMAs. Taking as a starting point any WDN clustering solution, i.e., the solution obtained with Newman's fast algorithm for community detection, the novel algorithm operates by exploring changes in the community of belonging to segments lying in the boundary between adjacent communities, by applying an optimization inspired by the simulated annealing technique. The applications of the novel modularity formulation and optimization algorithm to two case studies yield well-performing clustering solutions in terms of engineering judgment criteria, such as the low number of inter-DMA boundary pipes, uniformity of DMAs and hydraulic performance.
•A single IDF model valid for various return periods and durations is developed.•New scaling models of design rainfall curves are presented.•Adjusted rainfall event durations are considered in the ...context of scale invariance.•Parsimonious intensity–duration–frequency (IDF) structure is obtained.•Good fit to quantile predictions of extreme rainfall data for specified durations.
This paper deals with intensity–duration–frequency (IDF) curves, which express the relationship between average rainfall intensity and event duration for various probabilities of non-exceedance (or return periods) for the design/analysis of hydraulic interventions and infrastructures in riverine and urban drainage contexts. New scaling models are proposed to develop a single IDF model valid for all durations, from below 1 h to 24 h. In these models, the scale invariance is applied to rainfall intensity to obtain a parsimonious IDF structure capable of defining a family of IDF curves at various return periods. The main novelty consists of the formulation of simple and multiple scale invariance based on adjusted design event durations. The parameterization is carried out in two phases: in the first phase, the adjustment size is searched for iteratively while the other parameters of the IDF structure are directly obtained in cascade; in the second phase, which enables considering different reliability levels for extreme rainfall data as a function of sample length at different durations, parameter refinement is carried out by means of a local optimization algorithm. The second step accommodates data samples of different extension as a function of available data at different durations. The application to four case studies at various latitudes in Europe, namely Helsinborg (Sweden), Frauenwald (Germany), Pavia and Erice (Italy), proves the IDF structure to fit well the quantile predictions of extreme rainfall data for specified durations below and above one hour.
The positioning of quality detection points as well as the frequency of sampling is a crucial aspect for the implementation of Water Safety Plans (WSPs), which have been proposed worldwide to ensure ...water quality and to minimize the risk from contamination in water distribution networks (WDNs). In this regard, some international legislations and best practices about quality of drinking water suggest very fine sampling frequencies, but they do not specify where the detection points should be located in a WDN. In this paper, three different approaches, based on empiricism, optimization and topology, respectively, were applied to locate detection quality points in a WDN. The comparison highlighted that empirical approach commonly adopted by water utility practitioners is unsatisfactory. The optimization-based approach, although performing significantly better, is difficult to apply, since it requires a calibrated hydraulic model. The topological approach, based on the use of the betweenness centrality and not requiring any hydraulic information and simulation, proves to be effective, and it can be easily adopted by water utilities to identify the location for quality detection points, due to its simplicity compared with the optimization-based approach.
This paper presents a novel algorithm driven by the minimization of the transport function for the partitioning of water distribution networks (WDNs) into district metered areas (DMAs). The algorithm ...is based on the linear programming (LP) embedded inside a multi-objective genetic algorithm, which enables engineering criteria, such as the minimization of the boundary pipes and the maximization of the uniformity of DMAs, to be considered in the partitioning. Furthermore, the application of the algorithm on the dual network topology based on segments and valves guarantees that configurations of DMAs that respect the real positions of isolation valves for WDN partitioning are obtained. After being described on a small WDN, it is successfully validated on a large size WDN, proving better performance than other algorithms in the scientific literature for the generation of engineeringly appealing DMA configurations, with almost identical hydraulic performance to the unpartitioned WDN. HIGHLIGHTS A clustering based on transport function minimization is proposed.; The dual topology based on segments and valves enables the real valve positions to be considered in WDN partitioning.; The transport function minimization by LP is embedded in the multi-objective optimization to incorporate engineering judgment criteria.; Engineeringly appealing DMA configurations are obtained in the applications to a real WDN.;
This paper presents the partitioning of the closed water distribution network (WDN) serving the city of Pavia, Italy. As a thus far poorly explored aspect in the scientific literature, clustering for ...the definition of size and extension of district metered areas (DMAs) and of inter-DMA boundary pipes is performed by ensuring that the DMAs respect the altimetric areas of the WDN by leaning on a modified formulation of modularity. To define the boundary pipes to be closed or alternatively fitted with a flow meter for the monitoring of DMA consumption, the dividing is performed with an innovative heuristic algorithm. This technique operates by sequentially implementing the boundary closures that do not cause significant head losses, to obtain an approximation of the Pareto front in the trade-off between number of flow meters installed and WDN reliability. In the last part of the work, the pumps present in the network are assumed to be equipped with the variable speed drive, and their hourly settings are optimized to regulate service pressure. Overall, WDN partitioning and pump setting optimization are proven to mitigate the service pressure and energy consumption of the WDN, offering evident and attractive benefits up to about 50% for water utilities.
This paper presents the comparison of five pressure-driven formulations in the context of water distribution network (WDN) modelling. These formulations, which relate nodal outflow q to users to ...demands d and nodal pressure heads h, were implemented inside the global gradient algorithm for the snapshot solution of the equations concerning mass and energy conservation at WDN nodes and pipes, respectively. The modelling of leakage nodal outflows as a function of pressure was also considered. The applications concerned two case studies, in which nodal demands were suitably amplified to lower service pressure below the desired values. This was done to stress the effects of the pressure-driven dependence q(h) in the WDN. The results showed that the formulations tend to behave similarly in terms of nodal outflows. Compared to a widely used formulation, which features a q(h) relationship with derivative discontinuities, the other four formulations analyzed tend to guarantee faster algorithm convergence, above all for simple and poorly interconnected WDNs, due to their smooth q(h) relationship. The results in terms of nodal pressure heads can be very different, above all for low values of h.
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