Improving operation of a complex headworks system for municipal use and hydropower production by mathematical programming

The paper presents a Mixed Integer Non Linear Programming (MINLP) model of the water resources system supplying Genoa, in northern Italy. The system presently features five reservoirs, three main river intakes, and two well fields. The hydrological regime is typically Mediterranean; water availability is however relatively abundant, so that drought issues are limited, especially now that water demand from the supply sources has decreased due to reduced population, deindustrialization and to improvement in the operation and maintenance of the water distribution network. In this context, it is worthwhile considering the possibility to relax an over-conservative management of resources, justif…

Valutazione delle alternative infrastrutturali per la riduzione del rischio di razionamento idrico delle aree urbane

Un modello di simulazione/ottimizzazione per la scelta delle alternative infrastrutturali in un sistema idrico complesso

Environmental Benefits and Economical Sustainability of Urban Wastewater Reuse for Irrigation—A Cost-Benefit Analysis of an Existing Reuse Project in Puglia, Italy

Besides benefits associated to increased water availability for irrigation, reuse projects of urban water can also provide positive environmental impacts, as they contribute to improve water quality of the receiving bodies by diverting wastewater from their outlet. This represents a typical win-win situation where significant synergies can be achieved between urban and agricultural sector, and the environment. These favorable conditions, however, do not necessarily imply that water reuse is either feasible from an economic perspective nor that the underlying supply chain is going to be triggered, if certain conditions are not met. Cost-Benefit Analysis (CBA) is considered a sound, theoretic…

A Cost–Benefit Based, Parametric Procedure to Screen Existing Irrigation and Municipal Supply Reservoirs for Wind Energy Storage

Pumped hydro storage (PHS) is one of the more suitable energy storage technologies to provide bulk storage of intermittent renewable energy sources (RES) such as wind. Since the main limiting factors to the expansion of this mature technology are environmental and financial concerns, the use of an existing reservoir can help mitigate both types of impacts. In addition, the high number of reservoirs for municipal and irrigation supply in many areas of the world makes the idea of using PHS as a relatively diffuse, open-market, technology for RES management attractive. These arguments in favor of PHS must, however, be convincing for investors and regulators from an economic standpoint. To this…

Selezione del tempo di ritorno ottimale della pioggia di progetto delle reti di drenaggio urbano

Climate regimes and yearly streamflow frequency analysis in Sicily

Yearly streamflow frequency analysis is performed in Sicily, Mediterranean’s largest island, using the index flow procedure, i.e. fitting a single probability distribution function (pdf) to the available yearly flow data scaled by their mean. This requires 1) the identification of homogeneous regions where L-moments’ observed variability can be ascribed to sample variability only, and 2) the estimation of mean annual streamflow by multiple regression analysis with some significant climatic and morphologic covariates. Rather than having defined geographical boundaries, the identified homogeneous regions should gather basins sharing similar morphologic and climatic features. Steps 1) and 2) a…

Use of the residual capacities of existing reservoirs as storage of the electricity produced by grid-connected intermittent RES plants, by means of pumped storage of water to a multi-day scale

Statistical sampling of water uses for leakage assessment via water budget

Regolazione dei sistemi idrici complessi – Parte I: ottimizzazione dei sistemi idrici

Il ruolo e le forme organizzative delle società di approvvigionamento primario

Regolazione dei sistemi idrici complessi – Parte II: gestione tecnico – economica dei sistemi

Screening Investments to Reduce the Risk of Hydrologic Failures in the Headwork System Supplying Apulia (Italy) – Role of Economic Evaluation and Operation Hydrology

The paper introduces and applies a methodology to screen investments aimed at reducing water supply risks due to hydrologic failures in headwork systems for municipal use, based on the principles of cost-benefit analysis. As risk includes both the probability of a failure and its effect, the methodology combines a simulation module of the system, fed by a stochastic hydrologic input to reproduce the probability distribution of the failures, with a metric for supply failure damage provided by the price – demand relationship for municipal water. Benefits are assessed as the averted damage compared to a base case without investments. This approach is then combined with the classic discounted c…

La regolazione di prezzo nel settore idrico: Proposte per un nuovo metodo tariffario

Identificazione del campione ottimale di consumi per la stima del bilancio idrico in un ATO: il caso di Siracusa

Evaluating Infrastructure Alternatives for Regional Water Supply Systems by Model-assisted Cost-benefit Analysis – A Case Study from Apulia, Italy

The main challenge associated to regional water supply systems planning lies in understanding the best infrastructure alternatives to improve service given a certain configuration of the resources system. While cost-effectiveness assessments are still widespread in this type of analyses, they do not account for the fact that, especially in mature systems, service improvements tend to follow the law of marginal diminishing returns, so that a cost – benefit assessment should be preferable. Both costs and benefits can be organized into a cost-benefit analysis (CBA) framework. In a complex system, a model reproducing its topology and characteristics better describes the impacts of the alternati…

Una metodologia per la selezione del tempo di ritorno ottimale della pioggia di progetto delle reti di drenaggio urbano

L'obiettivo del presente lavoro è quello di definire una metodologia per l'individuazione del tempo di ritorno ottimale della pioggia di progetto dell reti di drenaggio urbano.

Evaluation of statistical sampling for the assessment of residential consumption totals in water distribution networks

The paper provides insights into stratified sampling, a standard statistical technique that may be employed to assess domestic water use in water distribution networks. The basic idea is to use only a few meters to provide inference on the total water consumption of a network or of a district metered area through the knowledge of some additional stratification variables, such as household typology, size and occupants number. Since any sampling procedure assumes that the variance of the variable at stake is known, either a suitable amount of past consumption data is necessary, or a specific preliminary survey must be carried out, in order to define the sampling plan. An application with real…

Multi-year drought frequency analysis at multiple sites by operational hydrology - A comparison of methods

Abstract This paper compares two generators of yearly water availabilities from sources located at multiple sites with regard to their ability to reproduce the characteristics of historical critical periods and to provide reliable results in terms of the return period of critical sequences of different length. The two models are a novel multi-site Markov mixture model explicitly accounting for drought occurrences and a multivariate ARMA. In the case of the multisite Markov mixture model parameter estimation is limited to a search in the parameter space guided by the value of parameter λ to show the sensitivity of the model to this parameter. Application to two of the longest time series of …

Assessing the risk of water supply in drought-prone areas

Le infrastrutture idriche: finanziamento, regolazione e mercato

Contrariamente a quanto avvenuto in Europa negli ultimi quindici anni in molti altri settori dove le reti infrastrutturali possono essere considerati come monopoli naturali e come tali storicamente di proprietà pubblica, il settore idrico in Italia è stato sostanzialmente immune dal processo di introduzione anche parziale di forme di competizione nel mercato fra operatori. Le ragioni di tale difficoltà sono certamente di tipo oggettivo, quali le caratteristiche tecniche ed economiche che rendono molto più difficile la competizione rispetto ad altri settori quali l’energia e le telecomunicazioni, l’elevato valore della rete infrastrutturale rispetto al valore delle risorsa, le implicazioni a…

SELEZIONE DELLE ALTERNATIVE DI RIABILITAZIONE IN CONDIZIONI DI SCARSITÀ DI DATI MEDIANTE INDICI DI PERFORMANCE CONCISI

SELECTION OF REHABILITATION ALTERNATIVES OF WATER DISTRIBUTION SYSTEMS IN CONDITION OF LACK OF DATA BY CONCISE PERFORMANCE INDICES AND OPTIMIZATION TOOLS

Water distribution network robust design based on energy surplus index maximization

The aim of this paper is to show that energy surplus indices, such as resilience index, besides providing a very good indirect measure of water distribution network reliability to be adopted during the design phase, represent also a valuable and effective indicator of the robustness of the network in alternative network scenarios, and can thus be profitably used in condition of future demands uncertainty. The methodology adopted consisted of (I) multi-objective design optimization performed in order to minimize construction costs while maximizing the resilience index; (II) retrospective performance assessment of the alternative solutions of the Pareto front obtained, under demand conditions…

Assessing priority of intervention on water distribution networks with reduced information

Optimal Network Design with the Use of Reliability Constraints and Simulated Annealing Tecnique

Improving the resilience to drought of the Apulian water resources system – an hydroeconomic model

The paper presents a hydro-economic model of the Apulian water resources system, in southern Italy, i.e. a mathematical programming model of the allocations explicitly accounting for the different values of water and for hydrological variability at the appropriate time scale. Traditionally a water-scarce region, Apulia is now supplied by extra-regional regulated surface resources as well as by a coastal aquifer; altogether, they constitute a multipurpose system with conflicting uses: municipal, irrigation and, to a lesser extent, industrial supply. The system is at present affected by high streamflow variability and by a high level of water losses along the urban distribution networks. In t…

Simulation versus Optimization in the assessment of the resource opportunity cost in complex water resources systems.

Campionamento dei consumi per la valutazione delle perdite mediante l’esecuzione di bilanci idrici

Sistema di supporto alle decisioni negli interventi di manutenzione delle reti di distribuzione idrica in condizioni di informazioni limitate

L’uso dei modelli matematici per la valutazione del costo delle risorse in un sistema idrico complesso

SULLA DEFINIZIONE DELLE PERDITE NEI LATI DELLE RETI DI DISTRIBUZIONE PER LA SIMULAZIONE IDRAULICA NELL’AMBITO DEI MODELLI DI ASSET MANAGEMENT

Selection of rehabilitation alternatives in condition of data scarcity by concise performance indices

Modelli possibili per favorire l'industrializzazione del SII negli ATO meridionali

La simulazione delle portate giornaliere di un corso d’acqua tramite modelli markoviani a stato nascosto

La memoria valuta l’applicabilità dei modelli markoviani a stato nascosto (Hidden state Markov Models) per la simulazione delle portate giornaliere di un corso d’acqua. In questi modelli la variabile osservata è l’emissione di un processo markoviano con un numero discreto di stati, caratterizzato da una matrice di probabilità di transizione, che viene “ricoperto” da una certa funzione densità di probabilità. Il problema della selezione del modello consiste in questo caso nella scelta del numero di stati e del tipo di distribuzione di probabilità di appartenenza ad uno stato. Identificato il modello, la sua calibrazione consiste nella stima delle probabilità di transizione e dei parametri de…

Planning Rehabilitation Actions on Water Distribution Networks in Condition of Data Scarcity

The paper shows a viable approach to the selection of water networks rehabilitation actions, in condition of data scarcity and uncertainty, based on the use of four concise performance literature indices, allowing the analysis and identification of efficient, reliable and robust rehabilitation alternatives, even if assessed on the basis of a relatively small amount of data. A promising statistical sampling method of water consumptions is also described, that may be fruitfully employed within the proposed approach for drafting water balances at network district scale in order to quantify the extent of leakages. The illustrated case study shows that the selected indices are capable to describ…

Sensitivity of Regional Water Supply Systems Models to the Level of Skeletonization – A Case Study from Apulia, Italy

AbstractSimulation models supported by state-of-the-art software packages are nowadays available to explore operation rules of regional water supply systems or to select structural alternatives for improving long-term service performances.Given the, sometimes high, complexity of these systems, model calibration can become a lengthy procedure and many runs are necessary before obtaining convincing results. However, even after calibration, depending on system's complexity and the number of time steps investigated, a single run can take up to several minutes, even on state-of-the-art computers, so that simulation time can become a true bottleneck if such models are to be coupled with metaheuri…

Aspetti economici nelle strategie di gestione delle perdite idriche

L’obiettivo logico di ogni gestore efficiente è quello di eliminare completa-mente le perdite della rete di distribuzione, in quanto queste si associano ad incrementi di costi per la produzione e la distribuzione delle risorse, in termini di sovradimensionamento dei serbatoi, degli impianti di trattamento e delle tubazioni della rete. Tuttavia la completa eliminazione è impossibile, e in realtà va individuato il livello di perdite che si può tollerare e controllare. La definizione teorica dei livelli economici delle perdite idriche non è nuova. Già Parry nel 1881 discusse i costi e i benefici di una strategia di ridu-zione degli sprechi con ispezioni, uso di materiali e infrastrutture di bu…

Pianificazione degli investimenti nelle reti idriche per il miglioramento dei livelli di servizio

Selection of the Optimal Design Rainfall Return Period of Urban Drainage Systems

Abstract The aim of this work is to define a methodology to identify the optimal rainfall return period for the design of urban drainage systems. The choice of the optimal return period is made minimizing the total costs of the system: the sewer network is dimensioned for a set of possible design rainfall return periods, and the corresponding construction, maintenance and operation costs are evaluated. For each scenario, the total expected damage from flooding caused by rainfall events with return period greater than the design one is then estimated by hydraulic simulation. This methodology has been applied to a small urban catchment in Palermo (Italy).

Sampling of Residential Water Use for Leak Control via Water Budgets

Scheletrizzazione di modelli di sistemi di approvvigionamento idrico regionali – Un caso di studio

In questo lavoro viene esaminata la possibilità di ridurre i tempi di calcolo, mediante la "scheletrizzazione" dei modelli, adottando come caso di studio un sistema di approvvigionamento idrico regionale reale, modellato in ambiente AQUATOR. La scheletrizzazione è stata in origine introdotta nel campo dell'ingegneria idraulica al fine di includere nei modelli idraulici delle reti solo le parti dalla rete reale che hanno un significativo impatto sul funzionamento del sistema, riducendo l'onere computazionale ma permettendo comunque di ottenere risultati accurati ed affidabili (Walski et al., 2007; Eggener & Polkowski, 1976; Shamir & Hamberg, 1988a,b). Il principio di base della scheletrizzaz…

L'approvvigionamento idrico primario

La sicurezza dell''approvvigionamento idrico per gli usi civili, irrigui e industriali nel rispetto dei vincoli di sostenibilità ambientale è una problematica che investe aree sempre più estese sia nei paesi sviluppati sia in quelli in transizione o in via di sviluppo. Fattori amplificanti di questa crisi sono la ridotta disponibilità di risorse e il contemporaneo aumento della popolazione e delle aree irrigate. La corretta gestione dei sistemi idrici complessi deve assicurare: • il soddisfacimento degli usi civili, irrigui e industriali, nonché di quelli ambientali; questi usi sono conflittuali, con specifiche esigenze e “disponibilità a pagare”, da armonizzare fra di loro e rendere compat…

Un metodo probabilistico per la valutazione del rischio idrologico in sistemi idrici ad usi plurimi

Ottimizzazione della gestione della rete di adduzione primaria di Acquedotto Pugliese S.p.A. tramite modelli di supporto alle decisioni: l'utilizzo del software Aquator

La Progettazione delle reti idriche con il metodo 'Simulated Annealing

Models of regional or municipal Public-Private Partnership (PPP) in order to favour the industrialization of the Integrated Water Service in the ATO's of Southern Italy

Exploring the Potential and the Boundaries of the Rolling Horizon Technique for the Management of Reservoir Systems with over-Year Behaviour

The paper presents a set of experiments on the Rolling Horizon Technique (RHT), applied to the management of a multi-reservoir, multipurpose water resources system with over-year behaviour. In the RHT, decisions on releases from reservoirs are taken for a number of time steps ahead (the Forecasting Horizon – FH) through an optimization model, based on the present water availability in reservoirs and on some forecasts of future inflows over the FH. Only the decision concerning the first time step (the current month) is then implemented, as new information on reservoir levels and forecasts becomes available so that the process can start again with updated information. The paper investigates h…

Teoria stocastica dei serbatoi, studio a scala mensile

The first step in the management and replacement strategy of water distribution network: the analysis of main failures

Comparison between Entropy and Resilience as Indirect Measures of Reliability in the Framework of Water Distribution Network Design

Abstract The aim of this paper is to investigate which between the entropy and resilience indices represents a better indirect measure of reliability in the framework of water distribution network design. The methodology adopted consisted of (a) multi-objective optimizations performed in order to minimize costs and maximize reliability, expressed by means of one of the indirect indices at time; (b) retrospective performance assessment of the solutions of Pareto fronts obtained. Two case studies of different topological complexity were considered. Results showed that indices based on energetic concepts (resilience and modified resilience) represent a better compact estimate of reliability th…

Applicabilità della teoria stocastica dei serbatoi nei sistemi idrici complessi

A BASIC DECISION SUPPORT SYSTEM FOR IMPROVING SERVICE LEVEL IN INTERMITTENT WATER DISTRIBUTION SYSTEMS

WATER DISTRIBUTION NETWORKS REHABILITATION BASED ON A SMALL INFORMATION DATASET

A multi-scenario Decision Support System for real-time operation of over-year multi-reservoir system 2. DSS simulation

A companion paper (Arena et al, 2019) has introduced the architecture of the DSS and has described its governing equations. In a real-time, dynamic decision-making context, it is a tool to support decisions at the current time step concerning water allocations to municipal demand centres and irrigation districts as well as additional intakes from costly water sources in a water resources system featuring reservoirs with over-year behaviour. The DSS is designed as a linearized MIP (mixed integer programming) optimization model and as such, it includes an objective function and constraints on 1) mass balances at system’s nodes, 2) systems’ topology, 3) component’s capacity, 4) spills, as well…

Water transfer from Basilicata to Puglia: a technical, economic and institutional challenge

The necessity of supplying Puglia by transfer of water resources from Basilicata (250 Mm/year mainly for civil use but also for agricultural and industrial uses) and another bordering region (Campania for 200 Mm/year only for civil use) arises from the scarcity of water resources inside Puglia, where precipitation is very low (400 mm/year), rivers are few and with limited watersheds and costal aquifers are overexploited with salt intrusion. Moreover recent droughts have pointed out the need for revising water supply policy in Puglia, looking for the increment of the transfer of water resources from Basilicata (50 Mm/year) and Campania (32 Mm/year) and the development of feasibility studies …

A simulation/optimization model for selecting infrastructure alternatives in complex water resource systems

The paper introduces a simulation/optimization procedure for the assessment and the selection of infrastructure alternatives in a complex water resources system, i.e. in a multisource (reservoirs) multipurpose bulk water supply scheme. An infrastucture alternative is here a vector X of n decision variables describing the candidate expansions/new plants/water transfers etc. Each parameter may take on a discrete number of values, with its own investment cost attached. The procedure uses genetic algorithms for the search of the optimal vector X through operators mimicking the mechanisms of natural selection. For each X, the value of the objective function (O.F.) is assessed via a simulation mo…

Aspetti tecnici ed economici dei Piani d'Ambito del Servizio Idrico Integrato

Statistical analysis of water main failures in the distribution network of an italian municipality