Giovanni Grillone

Empirical Investigation of Curve Number Method Parameters in the Mediterranean Area

AbstractThe curve number (CN) method is widely used as a technique for estimating surface runoff depth from rainstorms. This simply lumped method is based on the main parameter CN, which represents the lumped expression of basin absorption, and on a parameter that represents interception, infiltration during the early part of a storm, and surface depression storage, called initial abstraction. In this paper, CN is evaluated at the basin scale from rainfall-runoff multiday events, in the observation period 1940–1997 (recorded length mean equal to 20xa0years) for 61 Sicilian basins with three different methods: NEH4 method, asymptotic fitting method, and a least-squares method. A first analysis of Sicilian watershed behavior indicates a major occurrence of standard CN response (43 basins), as opposed to a complacent response (10 basins), and a few cases of violent behavior (3 basins). For basins with complacent behavior a modified formula of a runoff CN equation is proposed. The original assumption of the ini...

Estimation of Daily Solar Radiation from Measured Air Temperature Extremes in the Mid-Mediterranean Area

AbstractDaily solar radiation Rs at ground level is a necessary input variable required for the evaluation of evapotranspiration and crop growth, development, and yield-simulation models. Nevertheless, it is measured in few weather stations and at many locations it is not observed; also, available Rs temporal series are generally no longer than a few years. A valid surrogate of Rs measurement is the diurnal air-temperature range (ΔT); indeed, ΔT is inversely proportional to cloudiness and therefore could be a good indicator of atmospheric transmittance. As opposed to Rs, daily maximum and minimum air temperatures are measured at many locations and their observations in developed countries began in the 19th century. For this reason, several models that permit Rs indirect evaluation from air-temperature data have been suggested in the literature. The most famous models are the simple Hargreaves-Samani (HS) formula, many times recalibrated by the authors, and the Bristow-Campbell model, which has recently be...

Curve Number: Empirical Evaluation and Comparison with Curve Number Handbook Tables in Sicily

AbstractThe curve number (CN) method is widely used for estimating direct runoff depth from rainstorms. The procedure is on the basis of the parameter CN, a lumped expression of basin absorption and runoff potential, and a second parameter, initial abstraction (IA), which represents the interception, infiltration, and surface depression during the early part of a storm. The evaluation of CN in Sicily at a basin scale from rainfall-runoff multiday events is done using rainfall-runoff observations during the period 1940–1997 (mean record length of 20xa0years) in 61 Sicilian watersheds using three different methods: (1)xa0the national engineering handbook, sectionxa04 hydrology (NEH4) method (NEH4M) (the median CN for the annual flood events); (2)xa0asymptotic fitting of ordered and natural data; and (3)xa0least-squares method using rainfall-runoff using both ordered and natural data. Asymptotic fitting showed a major occurrence of the standard CN response (43 basins), with a lesser complacent response (10 basins), an...

Simplified Probabilistic-Topologic Model for Reproducing Hillslope Rill Network Surface Runoff

AbstractThis work presents a simplified probabilistic-topologic model for reproducing rill network surface runoff on a square-plane hillslope. The model requires only two parameters: the first is related to the production capacity of overland flow of the hillslope, at the initial conditions of the process, and the second depends on the sinuosity of the rill network. From a hydrological point of view, the following parameters account for the effects that essentially delineate the hydrologic response of a natural hillslope: rainfall intensity, hillslope roughness, and slope. Obviously, the reliability of the model is pending experimental validation that has only just begun. However, a preliminary experiment conducted on a 1.0×1.3-m test plot, with variable slope, has produced promising first results.

Probability Distribution of Peak Discharge at the Hillslope Scale Generated by Hortonian Runoff

AbstractIn this work, the probability distribution of peak discharge at the hillslope bottom is determined hypothesizing a prevalent Hortonian mechanism of runoff production for a given rainfall duration. As is well known, the probability distribution of peak discharge depends on the probability of both the rainfall event as well as that of the antecedent soil moisture conditions. In particular, the probability of the rainfall event is calculated according to the familiar rainfall duration–intensity–frequency approach, whereas the ecohydrological method from the literature is used here to define the probability of the antecedent soil moisture conditions. The latter depends on a set of parameters describing the dynamic interactions between average climate, soil and vegetation. By using the Monte Carlo procedure, the peak discharge is derived for a given rainfall duration and for each antecedent moisture condition/rainfall intensity pair from a physical-based model from the literature, by coupling the analy...

River Conservation and Phytodepuration in a Mid-Mediterranean Streambed: A Sicilian Case Study

AbstractFor landslide mitigation purposes, a system of two screen dams was created along the main channel of the Capreria River in Sicily. The de facto constructed wetlands occasioned behind the flow-path barriers produced, for several years, an appreciable reduction of organic load of the upstream municipal wastewaters from the nearby town of Riesi, Italy. This coincidence inspires the prospect of promoting a multifunctional role for these slope-stabilization works, thereby allowing them to be viewed from an intriguing and innovative planning perspective.