Trophic State and Toxic Cyanobacteria Density in Optimization Modeling of Multi-Reservoir Water Resource Systems

The definition of a synthetic index for classifying the quality of water bodies is a key aspect in integrated planning and management of water resource systems. In previous works [1,2], a water system optimization modeling approach that requires a single quality index for stored water in reservoirs has been applied to a complex multi-reservoir system. Considering the same modeling field, this paper presents an improved quality index estimated both on the basis of the overall trophic state of the water body and on the basis of the density values of the most potentially toxic Cyanobacteria. The implementation of the index into the optimization model makes it possible to reproduce the conditions limiting water use due to excessive nutrient enrichment in the water body and to the health hazard linked to toxic blooms. The analysis of an extended limnological database (1996–2012) in four reservoirs of the Flumendosa-Campidano system (Sardinia, Italy) provides useful insights into the strengths and limitations of the proposed synthetic index

Improved Implicit Stochastic Optimization technique for multireservoir water systems under drought conditions

Drought is a creeping phenomenon, making its onset and end difficult to determine. Damages from droughts can exceed those resulting from any other natural hazard, although it is difficult to assign a monetary value to them. In the Mediterranean area a severe drought period occurred over the years 2000-2002 and economic losses from that drought exceeded 250 million euros in Sardinia (Italy) (source: ENAS Regional Water Authority). Currently, technological developments and environmental modelling tools are improving our ability to more effectively manage water supply systems. Models can provide decision makers with better and more timely data and information. In this paper a methodology is proposed to support water decisions by selecting and evaluating reservoir operating rules based on hydrological scenarios generated from historical records. The methodology includes optimization and simulation tools. In particular, the paper presents some improvements to the traditional Implicit Stochastic Optimization (ISO) approach that overcome some severe limitations affecting previous works. Thanks to the collaboration with Regional Water Authorities in Southern Italy, the proposed methodology has been tested in the Agri-Sinni water system. Specifically this investigation focuses on: 1) Defining the reservoir operating rules based on correlations between releases, storages and inflows in a risk management approach of drought events; 2) Analyzing the significant reduction of computational time the user can get by applying the ISO technique in a GRID computing approach

Morphology of the salient of tuerredda beach (Sardinia, Italy) and hydrodynamic along the shoreline

On sandy shores, offshore obstacles create wider beaches, termed salients and tombolos, due to sediment deposition in their lee. The Authors quantified the shape and dimensions of salients formed in the lee of a natural reef and island in south Sardinia (Italy) and found that morphological results were in good agreement with previous investigations through aerial photographs of the coastlines of south eastern Australia and new Zeeland. This paper presents some preliminary results on the salient morphology and complex hydrodynamic behaviour near an island. The beach investigated in this work, known as the Tuerredda beach, is located in the south coast of Sardinia, the shoreline being characterised in the central part by a salient-shape due to the homonymous island. It is expected that the shoreline would be complex in its evolution over time due to the high variability of wave-induced currents and the random instability of the near natural mouth of a seasonally ephemeral stream

Field measurements of tug waves in the Cagliari Harbor, Italy

Field measurements of ship-generated waves were performed in the Cagliari Harbor where tugboats are significant wave generators that can adversely affect small-sized moored vessels. A method is proposed in which the major characteristics of the ship-generated waves in areas where wind waves and swell occur can be assessed and presented. The requirements and limitations of the method are also discussed. The results of the method application to field data were compared to an extensively used empirical equation from the literature for the prediction of the maximum wave height generated by tug passages. Although this comparison was affected by the uncertainties in the formation and propagation of ship-generated waves, it confirmed the practical validity of the proposed method