Teoria stocastica dei serbatoi - modellazione e potenzialità

Ecohydrology in Mediterranean areas: a numerical model to describe growing seasons out of phase with precipitations

Analisi multispettrale finalizzata al monitoraggio degli invasi in Sicilia: limiti e potenzialità

La diffusione crescente di laghetti collinari sul nostro territorio ha suggerito la possibilità di avviare un’attività di ricerca volta ad identificare la portata del fenomeno, la sua evoluzione nel tempo e l’incidenza che esso può avere sul bilancio idrologico e sulla stima della risorsa idrica disponibile. Con questo primo lavoro si è iniziato ad indagare i limiti e le potenzialità delle tecniche di elaborazione di dati remoti nell’identificazione degli invasi, di vario tipo, e nella stima della risorsa idrica da essi intercettata. La metodologia, basata sulla classificazione d’immagini multispettrali, è stata esaminata per diverse risoluzioni spaziali ed ha permesso di conseguire una sti…

EFFETTI DELLE VARIAZIONI CLIMATICHE SULLA VEGETAZIONE IN AMBIENTE MEDITERRANEO

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…

Teoria stocastica dei serbatoi - Studio a scala mensile

Influenza della misura di verosomiglianza nello studio di incertezza nella modellazione afflussi deflussi di un bacino mediterraneo

Il clima nell'isola? Tende all'aridità, lo dicono le variabili pioggia e temperatura

Gestire l’incertezza parametrica nell’utilizzo di un modello di deflussi giornalieri di tipo shot noise

Investigating the Reliability of Stationary Design Rainfall in a Mediterranean Region under a Changing Climate

Extreme rainfall events have been more frequent in recent decades, potentially as a climate change effect. This has been leading to a higher risk of the failure of existing hydraulic infrastructures, and to a higher awareness regarding the unreliability of design rainfall calculated with reference to historical data recorded in the last century. With this in mind, the present study questions the stationary assumption of the rainfall Depth–Duration–Frequency curves commonly used in Sicily, the biggest island of the Mediterranean Sea. Quantiles derived from the most up-to-date regional method, regarding Sicily, based on observations in the period 1928–2010, have been compared with those extra…

Un nuovo metodo per lo studio di stagionalità nelle serie idrologiche

Utilizzo degli l-moments per l’analisi regionale delle portate di piena in Sicilia. Atti del XXX Convegno di Idraulica e Costruzioni Idrauliche.

A performance based approach for the analysis of urban water distribution systems under drought conditions

The present study proposes some performance indicators for analysing urban water distribution system characterised by intermittent supply service. Specific indicators have been proposed for investigating the reduction of quality of water service under resources scarcity conditions. A modelling procedure has been implemented in order to allow for analysing complex network schemes in which users self adapt to scarcity conditions. The procedure has been applied to analyse the performance of an existing supply system in Palermo (Italy). The network and users’ behaviour in intermittent distribution conditions have been monitored in order to calibrate the model and verify the reliability of the p…

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…

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…

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 …

Regional frequency analysis of extreme precipitation in Sicily

Influence of rating curve uncertainty on daily rainfall–runoff model predictions

River discharge observations are usually affected by uncertainty, which is due to many concurrent causes and strongly affects the response of rainfall-runoff models. The present paper is aimed at studying the influence of imperfect rating curve knowledge on the uncertainty of the response of a daily conceptual linear-nonlinear rainfall-runoff model. To describe the impact of imperfect rating curve knowledge, simulations have been conducted using a conceptual rainfall-runoff model and continuous daily series of rainfall, air temperature and discharges recorded in a Sicilian catchment. The GLUE procedure was used to introduce the uncertainty of the rating curve in a classical rainfall-runoff …

The Peer Obervation: "Mentore" Project at the University of Palermo

During the last six years, at the University of Palermo, a group of academics has been involved in a project called “MENTORE” (“Modifying and ENhancing Teaching through peer Observation and Reflections with Experts”). The objectives of the project are: to help teachers improve their teaching, through the help of two mentors; to experiment new approaches in pilot courses to extend, if useful, to other ones; and to change the traditional model of academic teaching based on one single teacher with the class to go towards a model where there is a group of teachers working together in search of improvements. All the participants of the MENTORE project attend to lectures/workshops on teaching and…

Revisione critica del modello SMB attraverso un caso studio nel mediterraneo

Development of a regional flood frequency analysis using L-Moments approach for gauged and ungauged catchments of Sicily. Atti del International Workshop on Hydrological Extremes “Observing and modelling exceptional floods and rainfalls”.

Produttività dell’ulivo e dinamiche di umidità del suolo

Transient Soil Moisture Dynamics and Climate Change in Mediterranean Ecosystems

Plants in Mediterranean ecosystems have developed different strategies to cope with transient soil-moisture dynamics induced by the markedly out of phase seasonal behavior of rainfall and temperature. Deep-rooted plants use the soil moisture stored in the wet winter (extensive users), while shallower rooted plants exploit both the wet season storage and the more sporadic growing season rainfall (intensive users). Using stochastic models of soil moisture dynamics, we present an analytical and numerical description of the probabilistic structure of the soil-moisture storage at the beginning of the growing season in relation to the dynamics of the wet season, and then study its evolution durin…

Analisi di incertezza associata a differenti periodi di campionamento in un modello giornaliero afflussi-deflussi

Il progetto Mentori per la Didattica dell’Università degli Studi di Palermo: l’estensione del numero dei partecipanti, la figura del Mentore Senior e le esperienze di innovazione didattica

L’esperienza del Progetto Mentore (PM) nasce nel 2013 dalla percezione, da parte di diversi docenti dell’Ateneo di Palermo, che l’Accademia italiana stesse abbandonando a sé stessa la funzione didattica, confidando di fatto nelle capacità di ognuno di organizzarsi, aggiornarsi e valutarsi (Felisatti, Scialdone, Cannarozzo, & Pennisi, 2019; Caradonna, Morale, Pace, Scargiali, Scialdone, & Auteri, 2020). Tale impressione era tra le altre cose basata sul fatto che nessuno dei sistemi di valutazione dei docenti universitari (il processo di abilitazione scientifica nazionale, ma anche la stessa valutazione della qualità dei corsi di studio) mettesse enfasi sulla necessità da parte del do…

Annual runoff regional frequency analysis in Sicily

Abstract This paper performs annual runoff frequency analysis in Sicily, Italy using the index runoff method. Homogeneous regions, not necessarily defined by geographical boundaries but sharing common features from a morphologic and climatic standpoint, have been identified. For each region a single probability distribution function can be fitted to the available annual runoff data scaled by the index runoff. Starting from an initial dataset of 105 hydrometric stations, 57 stations have been selected using heuristic criteria associated with the Hosking and Wallis’s discordancy measure. The Mantel tests have been then applied to find out the physical and morphological parameters best correla…

Development of a regional flood frequency analysis using L-Moments approach for gauged and ungauged catchments of Sicily

Studying The Hydrological Response Of Urban Catchments Using A Semi-Distributed Linear Non-Linear Model

A conceptual rainfall-runoff model for urban catchment, which incorporates, semi-distributed modelling concepts has been developed. In the proposed model, the catchment is divided in external sub-catchments connected to the drainage network. Each external sub-catchment is modelled as two separate conceptual linear elements, a reservoir and a channel, one for the pervious part, the other for the impervious part of the drainage area. The drainage network is schematised as a cascade of non-linear cells and the flood routing is simplified in the form of kinematic wave and represented as a flux transfer between adjacent cells. Tests carried out using data from the Parco d'Orleans experimental ca…

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…

Distribuzione spaziale dei trend pluviometrici in Sicilia (1921-2000)

L'incertezza parametrica in un modello di previsione di deflussi giornalieri per bacini effimeri

Analysis of uncertainty associated to different periods of sampling in a daily rainfall-runoff model

Olive yield as a function of soil moisture dynamics

This study introduces a water-driven crop model aiming to quantitatively link olive yield to climate and soil moisture dynamics using an ecohydrological approach. A mathematical model describing soil moisture, evapotranspiration and assimilation dynamics of olive orchards is developed here. The model is able to explicitly reproduce two different hydroclimatic phases in Mediterranean areas: the well-watered conditions in which evapotranspiration and assimilation assume their maximum values and the real conditions where the limitations induced by soil moisture availability are taken into account. Annual olive yield is obtained by integrating the carbon assimilation during the growing season, …

Transient soil-moisture dynamics and climate change in Mediterranean ecosystems

[1] Plants in Mediterranean ecosystems have developed different strategies to cope with transient soil-moisture dynamics induced by the markedly out of phase seasonal behavior of rainfall and temperature. Deep-rooted plants use the soil moisture stored in the wet winter (extensive users), while shallower rooted plants exploit both the wet season storage and the more sporadic growing season rainfall (intensive users). Using stochastic models of soil-moisture dynamics, we present an analytical and numerical description of the probabilistic structure of the soil-moisture storage at the beginning of the growing season in relation to the dynamics of the wet season and then study its evolution du…

Implementation of a software about the probability theory of reservoirs.

Daily streamlow prediction with uncertainty in ephemeral catchments using the GLUE methodology

Abstract The Generalised Likelihood Uncertainty Estimation (GLUE) approach is presented here as a tool for estimating the predictive uncertainty of a rainfall–runoff model. The GLUE methodology allows to recognise the possible equifinality of different parameter sets and assesses the likelihood of a parameters set being acceptable simulator when model predictions are compared to observed field data. The results of the GLUE methodology depend greatly on the choice of the likelihood measure and on the choice of the threshold which determines if a parameters set is behavioural or not. Moreover the sampling size has a strong influence on the uncertainty assessment of the response of a rainfall–…

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…

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…

Integrazione di dati telerilevati in modelli idrologici: pre-elaborazione di immagini riprese da sensori aviotrasportati CASI ed ATM

ANALISI DEI TREND DI INDICI CLIMATICI IN SICILIA

L’INFLUENZA DELLA MORFOLOGIA SULLA DISTRIBUZIONE DELLE PIOGGE INTENSE

Le precipitazioni intense costituiscono uno dei principali pericoli naturali perché sono all’origine di processi, come innesco di frane o piene improvvise, che possono rappresentare una grave minaccia per la vita umana. Il problema di determinare la variazione spaziale delle precipitazioni intense e in particolare, di indagare sulle relazioni che intercorrono tra queste e la morfologia del territorio, è molto importante soprattutto per gli studi connessi alla realizzazione di efficienti sistemi di allerta e di allarme. Tuttavia la variabilità delle piogge intense con la morfologia è scarsamente studiata in idrologia. In questo lavoro si intende affrontare l’argomento a scala regionale, assu…

Analisi di alcune problematiche connesse alla modellazione della risorsa idrica.

La modellazione della risorsa idrica è una delle problematiche chiave degli studi i-drologici sia per esigenze operative, progettuali e gestionali, sia a scopo diagnostico in-terpretativo dell’ambiente in cui si opera. Nonostante si tratti di un argomento su cui tantissimi hanno lavorato e prodotto, nuove potenzialità, nuove esigenze e l’esistenza di problemi ancora irrisolti rendono la questione sempre feconda. In questa memoria si vuole descrivere l’attività svolta in proposito presso il DIIA dell’Università degli studi di Palermo nel corso di oltre 10 anni. Nel caso specifico della realtà siciliana la presenza di corsi d’acqua a carattere tor-rentizio e la forte variabilità spaziale e te…

Attività di monitoraggio di corpi idrici fluviali per l’individuazione dello stato di qualità: applicazione al bacino del fiume Oreto

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…

Uncertainty in Quali-Quantitative Response of a Natural Catchment on a Daily Basis

Critical analysis of thermal inertia approaches for surface soil water content retrieval

The “thermal inertia” method to retrieve surface soil water content maps on bare or sparsely-vegetated soils is analysed. The study area is a small experimental watershed, where optical and thermal images (in day and night time) and in situ data were simultaneously acquired. The sensitivity of thermal inertia to the phase difference between incoming radiation and soil temperature is demonstrated. Thus, to obtain an accurate value of the phase difference, the temporal distance between thermographs using a three-temperature approach is evaluated. We highlight when a cosine correction of the temperature needs to be applied, depending on whether the thermal inertia formulation includes two gene…

Spatial distribution of rainfall trends in Sicily (1921–2000)

Abstract The feared global climate change could have important effects on various environmental variables including rainfall in many countries around the world. Changes in precipitation regime directly affect water resources management, agriculture, hydrology and ecosystems. For this reason it is important to investigate the changes in the spatial and temporal rainfall pattern in order to improve water management strategies. In this study a non-parametric statistical method (Mann–Kendall rank correlation method) is employed in order to verify the existence of trend in annual, seasonal and monthly rainfall and the distribution of the rainfall during the year. This test is applied to about 25…

Analisi dei trend climatici in Sicilia

Analysis of trend existence in monthly precipitation in Sicily

The first step in the managment and replacement strategy of water distribution network: the analisys of main failures.

Investigating the changes in extreme rainfall series recorded in an urbanised area

The aim of this study is to investigate and quantify changes in the rainfall regime of the metropolitan area of Palermo characterised by increasingly strong urbanisation. The rainfall data, considered in this study, were collected on a yearly basis from eight rain gauges within and outside the metropolitan area of Palermo, Sicily, Italy. A preliminary analysis made on the annual total rainfall depths showed a global reduction of total annual rainfall, with two different trends: more regular for the series observed in the rain gauges within the urbanised area and more variable for the series observed in the rain gauges outside the area. A further analysis has been performed using the series …

Influenza della soglia di accettazione nell’analisi di incertezza

Monitoring activity to assess the quality conditions of a river: the case study of Oreto, Italy

Regional frequency analysis of extreme rainfall in Sicily (Italy)

The Peer Observation: “Mentore” Project at University of Palermo

During the last 6 years at the University of Palermo, a group of academics has been involved in a project called “MENTORE” (“Modifying and ENhancing Teaching through peer Observation and Reflections with Experts.”) The objectives of the project are to help teachers improve their teaching, through the help of two mentors; to experiment new approaches in pilot courses to extend, if useful, to other ones; and to change the traditional model of academic teaching based on one single teacher with the class to go toward a model where there is a group of teachers working together in search of improvements. All the participants of the MENTORE project attend to lectures/workshops on teaching and lear…

Utilizzo degli L-Moments per l’analisi regionale delle portate di piena in Sicilia.

Regional flow duration curves for ungauged sites in Sicily

Abstract. Flow duration curves are simple and powerful tools to deal with many hydrological and environmental problems related to water quality assessment, water-use assessment and water allocation. Unfortunately the scarcity of streamflow data enables the use of these instruments only for gauged basins. A regional model is developed here for estimating flow duration curves at ungauged basins in Sicily, Italy. Due to the complex ephemeral behaviour of the examined region, this study distinguishes dry periods, when flows are zero, from wet periods using a three parameters power law to describe the frequency distribution of flows. A large dataset of streamflows has been analysed and the param…

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

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

Monthly Hydrological Indicators to Assess Possible Alterations on Rivers’ Flow Regime

Assessing potential deviations of the fundamental river basins’ hydrological processes and streamflow characteristics from the “natural trajectory” represents a high-priority objective to understand the biological impact of altered flow regime on river ecosystems. Existing approaches are mainly based on the analysis of daily-based indicators of hydrologic alteration, which requires wide database, including “pre-impact” and “post-impact” daily flow data frequently unavailable. The hydrological modeling is commonly used to face data missing problems or reconstruct natural conditions, even if models, especially at the daily scales, are often complex and computationally intensive. The use of si…

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

Applicabilità della teoria stocastica dei serbatoi nei sistemi idrici complessi

Present-day use of an empirical wave prediction method

Knowledge of the offshore wave climate is key to the design of coastal engineering structures and to the study of shoreline evolution. To date, the available wave data have been limited both in time and space; even though there are several options for obtaining wave data calculated using complex numerical models at basin scale, design issues can in some cases be solved by means of simpler models. This paper shows whether, under certain conditions and in an enclosed basin, an old empirical model can provide results that are good enough to determine the design condition necessary for engineering purposes. The empirical model chosen to answer this question is called Sverdrup–Munk–Bretschneide…

Regional frequency analysis of extreme precipitation in Sicily, Italy

How different likelihood measures play a role in studying the uncertainty in the rainfall-runoff modelling of a mediterranean catchment

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…

A sensitivity analysis of a surface energy balance model to LAI (Leaf Area Index)

The LAI is a key parameter in hydrological processes, especially in the physically based distribution models. It is a critical ecosystem attribute since physiological processes such as photosynthesis, transpiration and evaporation depend on it. The diffusion of water vapor, momentum, heat and light through the canopy is regulated by the distribution and density of the leaves, branches, twigs and stems. The LAI influences the sensible heat flux H in the surface energy balance single source models through the calculation of the roughness length and of the displacement height. The aerodynamic resistance between the soil and within-canopy source height is a function of the LAI through the rough…

Trend dei deflussi in Sicilia

Gli effetti del cambiamento climatico si manifestano in maniera apprezzabile nelle modifiche subite da precipitazioni, temperatura e deflussi, in numerose località del pianeta, non solo con riferimento alla loro entità, più frequentemente indagata, ma anche riguardo alla loro variabilità nel corso dell’anno. In riferimento a questo secondo aspetto, con il lavoro qui riportato, si è voluto indagare circa l’esistenza o meno di un trend nella durata delle stagioni e nella quantità di risorsa idrica prodotta durante le stagioni stesse. Queste in genere sono identificate con criteri legati alle cadenze mensili che tengono conto solo sommariamente dell’effettiva variazione climatica stagionale; p…

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