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 model. Simulation is necessary as the O.F. contains, besides investment costs, also incremental operation costs and benefits that depend on the incremental water amounts which the alternative can provide. The simulation model transforms a thirty-year hydrologic input at daily/monthly scale in water allocations, accounting for the usual non-negativity constraints and using some simple, sytem-specific rules aimed at reducing spills and at sharing water deficits among demand centres. Different O.Fs and constraints have been tested, such as incremental financial cost/benefit minimization under various maximum water deficit constraints scenarios or cost/benefit mimization including scarcity costs. This latter approach has the advantage of implicitly allowing for the magnitude of deficits, but requires the assessment of deficit-scarcity cost relationships. The application of the procedure to a water resources system in south-western Sicily shows that the model is able to converge to results that are consistent with the planning options expressed by the selected O.Fs

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 cashflow approach of cost– benefit analysis to allow for the dynamics of both water supply and demand due to trends in population growth, individual consumption and, above all, planned reduction of losses in water distribution networks. The methodology is applied to screen a number of different supply-side projects for the headwork system supplying Apulia, in southern Italy featuring both regulated surface and groundwater resources and providing drinking water to over 4,000,000 persons. The procedure allows both ranking of single projects by their economical performances and the economic evaluation of combinations of different projects. The study also aims to assess the impact of the selected time scale, of cross-correlation among production sites, and of the specification of the demand function on projects' economic indicators. Results show that each modelling assumption has a considerable impact on the value of the economic indicators in absolute terms, but ranking of the different projects seems to be less sensitive to such modelling aspects

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

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 k to show the sensitivity of the model to this parameter. Application to two of the longest time series of streamflows available in Sicily (Italy) shows that the models can provide quite different results in terms of estimated return periods of historic droughts, although they seem to perform more uniformly when it comes to simulate drought-related statistics such as drought length, severity and intensity. The role of parameter selection for the multisite Markov mixture model and of the marginal probability of generated flows in providing results consistent with the characteristics of the observed series is discussed. Both models are applied to the system of sources supplying the city of Palermo (Sicily) and its environs showing the applicability of the newly developed multisite Markov mixture model to medium-to-large scale water resources systems

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, theoretically well-grounded tool to analyze the financial and economical sustainability of an investment. The paper presents the CBA of an existing reuse scheme in Puglia, in southern Italy, reclaiming wastewater for irrigation from a coastal area with growing recreational, beach-related activities. Supported by operational data, official statistics and sector documents, the CBA reveals that in almost all scenarios the existence of environmental benefits must be invoked in order to consider the project economically sustainable. Coherent screening of the different impacts, isolating the ones that are applicable to the specific case-study, shows that these benefits are mainly non-use benefits related to the aesthetic enjoyment of clean water in the reclaimed stretch of coastline where wastewater discharge may no longer take place or take place in a way that significantly reduce seawater pollutio

Sensitivity of regional water supply systems models to the level of skeletonization – a case study from Apulia, Italy

Simulation 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 metaheuristic optimization techniques, such as genetic optimization. This paper investigates the possibility to reduce computational time through skeletonization of the models. The regional water supply system of Apulia, Southern Italy, was adopted as a case study and the software package AQUATOR was employed to model the syste

Combined Endoscopic Stent-In-Stent Placement by Lumen-Apposing Metal Stents Through Self-Expanding Metal Stents for Simultaneous Malignant Biliary and Duodenal Obstruction

The palliation of simultaneous biliary and duodenal obstruction in patients with advanced pancreatic cancer is a clinically and technically challenging scenario. Endoscopic procedures are a valid alternative to surgical or percutaneous transhepatic biliary drainage. The availability of self-expanding metal stents (SEMSs) and lumen-apposing metal stents (LAMS) have expanded therapeutic options. We describe a case in which biliary and duodenal obstructions were treated successfully with the combined use of SEMS and LAMS devices. Endoscopic ultrasound-guided biliary drainage with the use of new LAMS and a duodenal SEMS can be a valid option in expert hands as a palliative and minimally invasive treatment for gastric outlet and biliary obstruction

A case of hemorrhagic shock due to massive upper gastrointestinal bleeding: from the differential diagnosis to the correct management

Upper Gastro-Intestinal Bleeding (UGIB) spans from minor bleeding to life-threatening events. Identification of early signs of shock, proper management of hemodynamically unstable patients, and correct risk stratification are essential for an appropriate diagnostic workup and therapy. This case reports a young man admitted to the emergency department with haematemesis. His medical history was unremarkable, without any risk factors for gastrointestinal bleeding. A few hours after admission, further episodes of haematemesis occurred, and the patient's condition rapidly deteriorated to irreversible shock. A contrast-enhanced computed tomography (CECT) revealed morphological features of chronic liver disease and oesophagal varices. The patient underwent upper gastrointestinal endoscopy, confirming oesophagal varices with massive bleeding. Although promptly applied, endoscopic hemostasis was ineffective, and the patient died twenty-four hours after admission. Based on this case, we reviewed the diagnostic and therapeutic approaches for patients with massive UGIB and provided a practical approach to this life-threatening emergency

Significaciones de jóvenes acerca del trabajo, capacitación laboral, proyecto de vida y tecnología

A fines del 2009, segúnla OIT81 millones de jóvenes se encontraban desempleados en el mundo. En el contexto en el que vive América Latina, los jóvenes son el grupo que se presenta con mayor fragilidad en lo que respecta al mercado laboral. Las causas son múltiples, y se busca entender la situación actual por la que atraviesa la cohorte de esta edad.