Storage facilities are key devices in mitigating the urban drainage impact on receiving water bodies, but their design is\ud still affected by high uncertainty. The analytical-probabilistic approach has recently raised interest, because the\ud facility performances are directly related to probability. Starting from statistically independent storm events,\ud distributions of the meteorological variables must be fitted. Rainfall series, recorded in three Italian raingauges,\ud were examined for appraising two main concerns: the choice of proper probability distributions for rainfall volume\ud and the sample sensitivity with respect to the analysis criterion. The analytical derivation of the model is then finally\ud discussed

[1] The assessment of the efficiency of a storm water storage facility devoted to the sewer overflow control in urban areas strictly depends on the ability to model the main features of the rainfall-runoff routing process and the related wet weather pollution delivery. In this paper the possibility of applying the analytical probabilistic approach for developing a tank design method, whose potentials are similar to the continuous simulations, is proved. In the model derivation the quality issues of such devices were implemented. The formulation is based on a Weibull probabilistic model of the main characteristics of the rainfall process and on a power law describing the relationship between the dimensionless storm water cumulative runoff volume and the dimensionless cumulative pollutograph. Following this approach, efficiency indexes were established. The proposed model was verified by comparing its results to those obtained by continuous simulations; satisfactory agreement is shown for the proposed efficiency indexes.Citation: Balistrocchi, M., G. Grossi, and B. Bacchi (2009), An analytical probabilistic model of the quality efficiency of a sewer tank, Water Resour. Res.,

Copulas are shown in this paper to provide an effective strategy to describe the statistical dependence between peak flow discharge and flood volume featuring hydrographs forcing a flood control reservoir. A 52 year time series of flow discharges observed in the Panaro River (Northern Italian Apennines) is used to fit an event‐based bivariate distribution and to support time‐continuous modeling of a flood control reservoir, located online along the river system. With regard to reservoir performances, a method aimed at estimating the bivariate return period is analytically developed, by exploiting the derived distribution theory and a simplified routing scheme. In this approach, the return period is that of the peak flow discharge released downstream from the reservoir. Therefore, in order to verify the reliability of the proposed method, a nonparametric version of its frequency distribution is assessed by means of continuous simulation statistics. Copula derived and nonparametric distributions of the downstream peak flow discharge are found to be in satisfactory agreement. Finally, a comparison of bivariate return period estimates carried out by using alternative approaches is illustrated.