This paper describes a heuristic approach for improving the performance of multipurpose reservoirs that have already been in operation for a certain number of years. The main characteristic of the method is that the analyst must first learn from the past experience of the manager and synthesize it into a simple operating rule. Then, the analyst must point out, with the help of the manager, what the acceptable modifications of such a rule are. After this has been accomplished, the optimal improvements of the operating rule can be obtained by using standard optimization techniques. Quite satisfactory results have been obtained by applying this approach to Lake Como (Northern Italy), which has been regulated since the end of World War II. In fact, the method shows that both flood protection on the lake shores and water supply to the downstream agricultural areas can be substantially improved, without lowering the mean yearly electricity production of the downstream run-of-river plants. For this reason the operating rule proposed by the method has been programmed on a microcomputer, which is now used every day by the manager as an essential support for his final decision. This and the fact that other actions suggested by this analysis have indeed been undertaken by the local authorities gave to this study the chance to have a positive and direct impact on the lake management. This paper presents a multiobjective analysis which explicitly quantifies the effectiveness of some proposed solutions: a modification of the actual operating rule (including the proper use of the available hydrometeorological data), the revision of the active storage, and the repaving and elevation of the sunken part of the town.The approach followed to solve the problem is of general interest and is therefore briefly described in the next section. Then, section 3 presents the main objectives of Lake Como management, together with the basic physical characteristics of the system. In section 4, the structure of the operating rule implicitly used by the lake manager during the period from 1946-1980 is extracted from the historical data and interpreted in terms of the management objectives. In section 5, the management problem is formulated and solved as a multiobjective mathematical programming problem, with a heuristic method which takes explicitly into account the past experience of the manager. In the following section, a particular operating rule is selected within the set of "efficient" operating rules and analyzed in detail in order to better estimate the improvements generated by this rule if it were to be applied in the future. Section 7 evaluates the surplus of benefit that can be gained by an efficient use of the information available in real time on the hydrometeorological conditions of the lake catchment, while section 8 describes the decision support system that has been put into operation. Such a system is based on a standard microcomputer, which, besides suggesting the optimal releases, can be used to forecast future inflows, to pe...
This paper describes some evidence of fractal order features in wind speed time series recorded at different observation stations both in USA and in Italy. Analysis were performed by using mono-fractal, multi-fractal and power spectra approaches. Results show that the average value of the box dimension for daily and hourly mean wind speed is D = 1.19 and D = 1.41 respectively, thus indicating that this kind of time series are fractal. The estimated average value of the Hurst exponent is H = 0.81 and H = 0.75 for daily and hourly time series respectively. From these Hurst exponents it is possible to infer the persistent behavior of wind speed. Furthermore, multi-fractal analysis shows that wind speed exhibits a bell-like shape spectrum with average width Δα = 0.47. Power spectra analysis has pointed out that wind speed time series behave as 1/f13 noise with average value of the β exponent of 0.46 and 1.37 for daily mean and hourly mean time series respectively. These latter results can be interpreted by saying that wind speed time series are Brown noise like
Air quality plans must be demonstrated to be economically sustainable and environmentally effective. This paper presents a full cost–benefit and environmental analysis of a large regional air quality plan involving several different actions covering a large spectrum of fields, from domestic heating to passenger and freight transport, from electricity generation to agriculture. The impact of each action is analyzed looking at the possible energy savings, greenhouse gases (GHG) emission reductions, the improvement in air quality, and the consequent decrease in external costs, namely the reduced impact on population health. The analysis is performed by applying a flexible and fast computer tool (RIAT+) that allows for a rapid simulation of different pollutant emission scenario, to assess different air quality indices (AQIs) over a regional scale domain. The results show that, in most cases, the economic savings exceed the implementation costs and thus that these actions can be introduced in air quality plans for the domain under study. The reduced health and climate costs, though relevant in absolute terms, are, in general, only a fraction of the economic benefits of energy savings. This is not true for the measures acting on improvements in electricity generation, since a reduction in power plant emissions (generally with high stacks, far from populated areas) does not significantly impact the air quality inside the region. A shift in energy production to renewable sources can instead provide noticeable effects on GHG emissions. This research raises some interesting and general questions about the adequacy of the methodologies applied to attribute costs (and benefits) to actions, improving a variety of sectors that are different from the one in which the measures are applied here.
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