Metodo speditivo per il dimensionamento di ali gocciolanti in pendenza

Metodo innovativo particolarmente semplice (solo due equazioni monomie) che consente di dimensionare ali gocciolanti comunque pendenti lungo i filari irrigui, massimizzando al tempo stesso il risparmio energetico (Baiamonte, 2018a). Il metodo pertanto sostituisce quello tradizionale basato su numerosi tentativi di calcolo di natura iterativa.

A rational runoff coefficient for a revisited rational formula

The Rational Formula (RF) is probably the most frequently applied equation in practical hydrology to compute the peak discharge, due to its simplicity and effective compromise between theory and data availability. Thus, after more than a century, the estimation of peak discharge through the RF is still an important and challenging issue in hydrology. The RF assumes response linearity and sometimes assumes that the return period does not depend on the runoff coefficient and neglects the time to ponding and the antecedent moisture condition. Moreover, the RF requires the critical duration of rainfall and the runoff coefficient to be estimated, both of which are highly controversial. This pape…

UNA SOLUZIONE ANALITICA DELLA DISTRIBUZIONE DI PROBABILITÀ DELLA PORTATA DI PIENA PER VERSANTI PERMEABILI

La conoscenza della risposta idrologica dei versanti è di fondamentale impor-tanza nel calcolo delle portate di piena, soprattutto per i piccoli bacini, in cui il comportamento del versante domina la risposta complessiva. È noto che la portata di piena, corrispondente alla durata critica della pioggia e, in particolare, la sua di-stribuzione di probabilità, sono necessarie in numerosi problemi pratici (il dimen-sionamento di opere idrauliche, la progettazione di infrastrutture urbane ed ex-traurbane, etc.). Nell’ipotesi che la formazione prevalente del deflusso superficiale avvenga secondo lo schema Hortoniano, tipico dei versanti con scarsa copertura ve-getale e modesta permeabilità dei su…

Analytical Approach Determining the Optimal Length of Paired Drip Laterals in Uniformly Sloped Fields

Microirrigation plants, if properly designed, allow for water use efficiency to be optimized and high values of emission uniformity to be obtained in the field. Disposing paired laterals, for which two distribution pipes extend in opposite directions from a common manifold, can contribute to reducing the initial investment cost that represents a limiting factor for small-scale farmers of developing countries where in the last decade, the diffusion of such irrigation systems has been increasing. The objective of this paper is to propose an analytical approach to evaluate the maximum lengths of paired drip laterals for any uniform ground slope, respecting the criteria to maintain emitter flow…

The influence of roughness geometry and shields parameter on flow resistance in gravel-bed channels

The spatial variability of bed particles of a gravel-bed channel is analysed and treated experimentally in order to simulate the effects of the arrangement of coarse bed elements on the flow resistance law. For the studied bed patterns, characterized by the concentration Γ of coarser elements arranged on the bed layer, a particle arrangement parameter α is proposed. The α parameter is useful for estimating the intercept b0 of the semi-logarithmic flow resistance law deduced by flume measurements carried out for the hydraulic condition of large-scale and transition roughness. The differences between the experimental friction factor parameter values and the ones calculated by the proposed sem…

Design of concave and convex paired sloped drip laterals

Abstract Properly designed microirrigation plants allow water use efficiency to be optimized and quite high values of emission uniformity to be obtained in the field. Disposing paired laterals so that two distribution pipes extend in opposite directions from a common manifold contributes to provide more uniform pressure to all laterals in thesystem. Towards this end, an analytical procedure to optimize the uniform pressure when designing paired drip laterals on uniform slopes has recently been proposed, based on the assumption that the variations of the emitters’ flow rate along the lateral and the local losses due to the emitters’ insertions could be neglected. More recently, an easy metho…

USING ROTATING SPRINKLER GUNS IN CENTRE‐PIVOT IRRIGATION SYSTEMS †

The use of centre-pivot irrigation systems has significantly increased in the last few decades, since they are easier and less time-consuming to manage compared to other irrigation systems. Standard high-pressure impact sprinklers, low-pressure spray sprinklers or LEPA (Low Energy Precision Application) systems are usually combined with a centre-pivot irrigation system (CP-SYS). However, when applying waste water or with reclaimed effluents that are extremely dirty, small nozzle sizes that require CP-SYS could get plugged. As an alternative to common centre-pivot irrigation systems, this paper analyses the ‘geometry’ of areas irrigated by rotating sprinkler guns in a centre-pivot irrigation…

Multiple Non-linear Reservoirs to Model Water Balance Components in Sandy Soils

In the hydrologic literature, to model water flow in unsaturated soils, the Richards equation is usually applied, allowing the main components of the hydrologic cycle, as rainfall partitioning into surface runoff and infiltration, to be determined. The Richards equation is highly nonlinear, making very challenging to derive analytical solutions. Recently, for constant rainfall intensity, under the simplified hypothesis of gravity-driven infiltration, and by assuming a capacitance framework, a simplified solution of the Richards equation that considers the Brooks and Corey hydraulic conductivity function was suggested. By maintaining the assumption that the infiltration process is dominated …

Simplified Interception/Evaporation Model

It is known that at the event scale, evaporation losses of rainfall intercepted by canopy are a few millimeters, which is often not much in comparison to other stocks in the water balance. Nevertheless, at yearly scale, the number of times that the canopy is filled by rainfall and then depleted can be so large that the interception flux may become an important fraction of rainfall. Many accurate interception models and models that describe evaporation by wet canopy have been proposed. However, they often require parameters that are difficult to obtain, especially for large-scale applications. In this paper, a simplified interception/evaporation model is proposed, which considers a modified …

Comparing Physical Quality of Forest and Pasture Soils in a Sicilian Watershed

Forest and pasture soils should have differing properties due, for example, to differing root characteristics or livestock trampling rates, but contradictory results are reported in the literature. The surface soil physical and hydraulic properties of five forest and pasture sites were determined in a Sicilian watershed. In general, forest soils had a significantly lower bulk density, b (by 17 to 35%), and a higher field saturated hydraulic conductivity, Kfs (by a factor of 3.4-11.5) than pasture soils. Differences between water retention characteristics of forest and pasture soils were low when high levels of organic matter, OM, content (> 7.1%) were detected for both land uses. The mean …

Effetti della copertura forestale sulle caratteristiche idrologiche del suolo

About time of occurrence of rainy days for Mediterranean and (sub)-Alpine areas

Sistema di irrigazione a perno centrale

L’invenzione consiste nell’impiego, nell’irrigazione pivot, dei comuni irrigatori rotanti che si utilizzano nei sistemi di irrigazione a pioggia (o per aspersione), che hanno il vantaggio, rispetto agli spruzzatori ed ai gocciolatori, di essere dotati di un ugello terminale di elevato diametro (4-30 mm). L’idea nasce quindi dalla ricerca di un sistema irriguo che conservi i benefici dell’irrigazione pivot (completa automatizzazione, manodopera limitata alla manutenzione degli apparecchi erogatori, elevata efficienza) e che al contempo rimuova del tutto il problema dell’occlusione degli apparecchi erogatori. Vengono così azzerati i costi di manodopera e, soprattutto, viene consentito l’impie…

Closed-form solutions of the energy balance equation for drip laterals under the Darcy-Weisbach resistance formula

Many studies have investigated easy methods to design drip laterals, as well as the best resistance equation to use, which is fundamental to accurately account for friction losses. This paper addresses both the features of lateral design relationships and the influence of the friction-loss equation on the design variables. First, simple closed-form solutions of the energy balance equation for both sloped and horizontal drip laterals are derived with the simplified Darcy-Weisbach resistance formula by assuming the Darcy friction factor as invariant versus the Reynolds number. Second, an error analysis is performed assuming the friction factor as constant in the design, which is compared to u…

Processi di infiltrazione in un mezzo altamente poroso: misure sperimentali e impiego di un modello semplificato a base fisica

Nel lavoro viene applicato un modello semplificato del processo di infiltrazio-ne, recentemente introdotto, valido per ammassi porosi altamente permeabili, in cui il gradiente di potenziale matriciale può essere assunto trascurabile rispetto a quello gravitazionale. Lo schema descritto si presta per interpretare il processo di infiltrazione che si attua nei residui di Posidonia oceanica (Linneo) Delile, accumulata nei siti di stoccaggio, per l’abbattimento della salinità a mezzo di dilavamento na-turale. Nel lavoro, vengono presentati i primi risultati ottenuti dal monitoraggio di alcune caratteristiche fisiche di interesse dei residui di P. oceanica, per il processo in esame e, in particol…

Influence of biochar on the physical, chemical and retention properties of an amended sandy soil

Soil porosity plays an important role in soil-water retention and water availability to crops, potentially affecting both agricultural practices and environmental sustainability. The pore structure controls fluid flow and transport through the soil, as well as the relationship between the properties of individual minerals and plants. Moreover, the anthropogenic pressure on soil properties has produced numerous sites with extensive desertification process close to residential areas. Biochar (biologically derived charcoal) is produced by pyrolysis of biomasses under low oxygen conditions, and it can be applied for recycling organic waste in soils and increase soil fertility, improving soil st…

A simple model of hillslope response for overland flow generation

This paper deals with the derivation of the hydrological response of a hillslope on the assumption of quick runoff by surface runoff generation. By using the simple non-linear storage based model, first proposed by Horton, an analytical solution of the overland flow equations over a plane hillslope was derived. This solution establishes a generalization for different flow regimes of Horton's original solution, which is valid for the transitional flow regime only. The solution proposed was compared successfully with that of Horton and, for the turbulent flow regime, to the one derived from kinematic wave theory. This solution can be applied easily to both stationary and non-stationary rainfa…

Quick and Slow Components of the Hydrologic Response at the Hillslope Scale

It is widely recognized that the Hortonian mechanism of runoff generation occurs in arid and semi-arid regions, generally characterized by high rainfall intensity on soils exhibiting low infiltrabilities. Differently, in steeply sloping forested watersheds in humid climates, by infiltrating through a highly permeable upper soil horizon, water moves beneath the soil surface determining a slow response. However, in most real cases, for example when in arid regions mountain forested areas take place, both (quick and slow) runoff generation processes coexist and together contribute to the hydrologic hillslope response. In this paper, based on analytical solutions of the hydrologic response, ins…

Discussion of “Unsteady Stage-Discharge Relationships for Sharp-Crested Weirs” by Firouz Ghasemzadeh, Salah Kouchakzadeh, and Gilles Belaud

I would like to thank the authors for writing this interesting article dealing with unsteady stage-discharge relationships for sharp-crested weirs. The operation of triangular and rectangular sharp-crested weirs in unsteady flow conditions was experimentally investigated. Results indicated the presence of looped rating curves, with transposition of the rising and falling limbs compared to that commonly observed in stream gauge ratings. The authors found that the deviation between steady and unsteady flow rates in the looped rating curves depends on the weir type and the hydrograph gradient (i.e., the temporal depth variation), especially when the latter changes rapidly. Finally, they propos…

Experimental Tests to Validate a Simple Procedure to Design Dual-Diameter Drip Laterals on Flat Fields

Multiple-diameter laterals reduce the total cost in microirrigation systems, however, the length of each sublateral should be determined carefully to assure appro-priate performance of emitter flow rates. The most accurate method is the numerical trial and error, which is time-consuming. A series of research efforts have been made to propose simple analytical design procedures. By using the power-law form of the Darcy-Weisbach formula, and equal emitters spacing for the sublaterals, Sadeghi et al. (Sadeghi et al. in J Irrig Drain E-ASCE 142:04,016,020, 2016) extended a previously introduced design solution for one-diameter laterals to tapered laterals. Recently, a simplified procedure to de…

Studio teorico-sperimentale sull'influenza del diametro dei contenitori nelle misure di erosione da impatto

The knowledge of impact erosion process constitutes an interesting theme research for its implications in many studies such as the seal formation, which results in a rapid drop in the infiltration rate, or the analysis of vegetation cover efficiency on rainfall erosivity. To determine impact erosion two different experimental techniques can be used: receiving or ejecting splash cups. Both experimental techniques, as well as theoretical approaches, showed a dependence of impact soil erosion to the splash cup diameter. In this paper, after a brief review of the main impact soil erosion models, a theoretical model is presented. The model is based on the assumption that the mass of soil eroded …

IL SOFTWARE IRRILAB PER IL RISPARMIO ENERGETICO NEL DIMENSIONAMENTO DEGLI IMPIANTI MICROIRRIGUI

I software per il dimensionamento idraulico dei settori microirrigui disponibili in commercio assicurano un'elevata uniformità della distribuzione idrica. Essi con-sentono di individuare le caratteristiche dei gocciolatori che funzionano con pres-sioni di esercizio ricadenti all’interno di un prefissato campo di variabilità ammis-sibile (h < hamm). Tuttavia, a quest’ultima condizione, non sempre corrisponde la soluzione più economica e di massima efficienza energetica. Non è detto, infatti, che i gocciolatori sfruttino l’intero campo di variabilità della pressione prescelto (hamm). Nel lavoro, viene illustrato il software IrriLab che, per settori irrigui di forma rettangolare e comunque …

Comparing different methods to determine soil physical quality in a mediterranean forest and pasture land

Soil physical quality (SPQ) can be assessed by different experimental methodologies and criteria and the optimal/critical values or ranges for SPQ indicators are still approximate. Sampling soils with minimal anthropic pressures should allow improvements in SPQ assessment. Different experimental methodologies and criteria were applied to sample a Mediterranean oak forest (Quercus ilex L.) and pasture land, in Sicily, with a varying degree of anthropic disturbance. Soil water retention was determined in the laboratory and the field, using the BEST (Beerkan Estimation of Soil Transfer parameters) procedure of soil hydraulic characterization. Capacity-based indicators, the S index, and locatio…

No-Till Soil Organic Carbon Sequestration Patterns as Affected by Climate and Soil Erosion in the Arable Land of Mediterranean Europe

No-tillage (NT) has been considered an agronomic tool to sequester soil organic carbon (SOC) and match the 4p1000 initiative requirements of conservative soil management. Recently, some doubts have emerged about the NT effect on SOC sequestration, often because observations and experimental data vary widely depending on climate and geographic characteristics. Therefore, a suitable SOC accounting method is needed that considers climate and morphology interactions. In this study, the yearly ratio between SOC in NT and conventional tillage (CT) (RRNT/CT) collected in a previous study for flat (96 samples) and sloping (44 samples) paired sites was used to map the overestimation of SOC sequestra…

Advances in designing drip irrigation laterals

It is known that using paired laterals, in which two distribution pipes extend in opposite directions from a common manifold, contribute to increasing water use efficiency (WUE). Recently, an analytical procedure to optimally design paired drip laterals on uniform slopes was proposed. More recently, this design procedure was simplified by deriving simple explicit relationships, as a function of 16 calibration constants, with relative errors that were less than 2%. In this paper, further simple design relationships are derived that require only 3 calibration constants, thus more readily obtainable results are produced and the influence of the flow rate and diameter exponents of resistance eq…

Metodo per la realizzazione di un’opera costruttiva modulare per la protezione del territorio e detta opera

The patent consists of an advanced technique for the modular elements construction, made with organic waste materials. These elements are used for land protection within the Soil and Water Bioengineering works. The linear work with anti-erosion function, consolidating and stabilizing of slopes, consists of modules (Roll Modular Fascine, RFM) made with the residues of vine pruning and with the residues of a marine plant, Posidonia oceanica beached. The work is made with waste materials. The material to make the module consists of vine prunings, collected with specialized agricultural machines. The fascines have a diameter of 40 cm and a length of 60 cm. Their density can be varied by acting …

Discussion of "Analysis of extreme rainfall trends in sicily for the evaluation of depth-duration-frequency curves in climate change scenarios" by Lorena Liuzzo and Gabriele Freni

In the original paper, the Authors investigated the presence of trends in extreme rainfall depths of duration d = 1, 3, 6, 12 and 24 hours, in Sicily. Trend analysis was performed by using the Mann-Kendal non-parametric test, which was applied at-site, for a number of 65 raingauges well distributed in the region, for the period 1950-2008. In order to overcome the gap of missing data, six years moving average series were considered in the Author’s analysis. In this discussion, the discussers highlighted some important observations about the paper presented by the Authors: i) The Authors applied the non-parametric Mann Kendall test to moving average series of rainfall data. The use of moving …

Sulla risposta idrologica di un versante a prevalente deflusso hortoniano

Variability of near-surface saturated hydraulic conductivity for the clay soils of a small Sicilian basin

Abstract Proper characterization of saturated hydraulic conductivity, Ks, of clay soils in a hillslope or a basin is still a challenge for soil science. In this investigation, the clay soils of the Maganoce (Sicily, Italy) basin were sampled at 19 sampling sites by the BEST procedure of soil hydraulic characterization. More OM implied less compact conditions (decreasing dry soil bulk density; coefficient of determination, R2 = 0.67), more stability to water of the soil aggregates (increasing water stable aggregates; R2 = 0.83) and, consequently, higher Ks values (R2 = 0.54). Variability of Ks was lower in the steeper zones of the basin than in the flatter ones. A comparison with the Ks data…

Effects of Biochar on Irrigation Management and Water Use Efficiency for Three Different Crops in a Desert Sandy Soil

This paper aimed at investigating if the application of biochar (BC) to desert sand (DS) from the United Arab Emirates (UAE), characterized by a very poor soil-water retention (SWR) and by a very low value of the maximum water available for crops (AWmax), could positively affect soil water balance, by reducing the irrigation needs (VIRR) and improving the irrigation water use efficiency (IWUE) and the water use efficiency (WUE). The analysis was performed for three crops, i.e., wheat (Triticum aestivum), sorghum (Sorghum vulgare) and tomato (Lycopersicon esculentum). BC was applied to the DS at different fractions, fBC (fBC = 0, 0.091, 0.23 and 0.33). Drip irrigation was adopted as a highly…

Empirical determination of the average annual runoff coefficient in the Mediterranean area

Runoff estimation in ungauged basin is a challenge for the hydrological engineers and planners. For an y hydrological study on an ungauged basin, a methodology has to be appropriately selected for the determination of runoff at its outlet. Several meth ods have been used to estimate the basin runoff production. In this study the empirical Kennessey m ethod to determine average annual runoff coefficien t, RC, is tested on 61 Sicilian basins characterized b y different climate conditions, surface permeabilit y, mean slope and vegetation cover. A comparison between observed and calculated RC showed that a calibration of the Kennessey model could be necessary. The slight and not satisfying impr…

Closure to “Simple Relationships for the Optimal Design of Paired Drip Laterals on Uniform Slopes” by Giorgio Baiamonte

The author appreciates the interest of the discussers of the paper “Simple Relationships for the Optimal Design of Paired Drip Laterals on Uniform Slopes” and wants to express his gratitude to Joaquin Monserrat and Javier Barragan for the opportunity to discuss the issues they raised. In their discussion, they questioned the use of analytical relationships to derive the design variables that are required for the optimal design of paired sloped laterals. This paper detected the Best Manifold Position (BMP = 0.24) to design optimal paired laterals and, as the discussers mentioned, allows the methodology introduced by Baiamonte et al. (2015) to be applied. Thus, the issues they questioned and …

Overland flow generation on hillslopes of complex topography: analytical Solutions

The analytical solution of the overland flow equations developed by Agnese et al. (2001; Hydrological Processes15: 3225–3238) for rectangular straight hillslopes was extended to convergent and divergent surfaces and to concave and convex profiles. Towards this aim, the conical convergent and divergent surfaces are approximated by a trapezoidal shape, and the overland flow is assumed to be always one-dimensional. A simple ‘shape factor’ accounting for both planform geometry and profile shape was introduced: for each planform geometry, a brachistochrone profile was obtained by minimizing a functional containing a slope function of the profile. Minima shape factors are associated with brachist…

Sulla distribuzione dei tempi di inter-arrivo delle piogge

La caratterizzazione probabilistica delle precipitazioni rappresenta un tema centrale in diverse aree di ricerca, come l'idrologia, la meteorologia, la climatologia, ed altre ancora, per le sue implicazioni sia teoriche sia pratiche. Un particolare interesse riguarda l’analisi della struttura probabilistica dei tempi di inter-arrivo delle piogge, alla scala giornaliera, che permette di inferire sulla probabilità della durata dei periodi di pioggia e dei periodi di siccità, dando conto sia della tendenza degli eventi di pioggia ad aggregarsi in cluster, che di quella alla persistenza dei periodi secchi. Nel presente lavoro, una siffatta analisi è stata condotta su alcune serie temporali di t…

Confronto tra differenti metodologie di valutazione della qualità fisica del suolo in un’area a pascolo e bosco della Sicilia

Il concetto di qualità fisica del suolo (SPQ, Soil Physical Quality) viene ormai largamente utilizzato, soprattutto in ambito agricolo. Un suolo agricolo di buona qualità fisica possiede caratteristiche strutturali favorevoli sia all’ancoraggio della coltura sia allo sviluppo dell’apparato radicale della pianta nonché un’adeguata ripartizione tra pori di diverse dimensioni, in modo da favorire simultaneamente l’areazione e la ritenzione idrica nel mezzo poroso. Per la valutazione della SPQ sono determinanti le misure di ritenzione idrica del suolo, che possono essere analizzate con diverse metodologie. Alcune indagini recenti segnalano tuttavia che la scelta della metodologia di analisi del…

Designing Trickle Irrigation Systems in Sloping Fields without Pressure-Compensating Emitters: Application of the IRRILAB Software

When designing trickle irrigation systems in sloped fields, the use of pressure-compensating (PC) emitters is generally preferred to ensure the emitter distribution uniformity regardless of the land topography and the variable operating pressures. However, the cost of PC emitters is generally higher than non-pressure-compensating (NPC) ones; moreover, the compensating membrane installed inside the emitters can lose elasticity due to the exposition to solar radiation, water quality, and chemical applications. Recently, the irrigation laboratory (IRRILAB) version 1.0 software application was developed to design microirrigation systems for rectangular and planar sectors when using NPC emitters…

Factors Influencing Point Measurement of Near-surface Saturated Soil Hydraulic Conductivity in a Small Sicilian Basin

Hydraulic conductivity of saturated soil, Ks, controls many hydrological processes. Parameterization of basin hydrological models in terms of Ks is complicated and uncertain owing to the very high spatial variability of this soil property. A small Sicilian basin was intensively sampled by the simplified falling head technique to obtain spatially distributed Ks data, and an attempt to explain their spatial variability on the basis of soil physical characteristics, digital elevation model-derived topographic attributes and land cover was carried out. High Ks values were obtained when clay content was low and both elevation and mean slope were high. Moreover, differences in Ks among land cover…

Delay times for saturation overland flow in forest soils

Structure alteration of a sandy-clay soil by biochar amendments

The aim of the present study was to investigate structure alterations of a sandy-clay soil upon addition of different amounts of biochar (f bc ). All the f bc samples were analyzed by high energy moisture characteristic (HEMC) technique and 1H nuclear magnetic resonance (NMR) relaxometry. HEMC was applied in order to evaluate aggregate stability of biochar-amended soil samples. 1H NMR relaxometry experiments were conducted for the evaluation of the pore distributions through the investigation of water dynamics of the same samples. The HEMC technique revealed improvement in aggregate stability through measurements of the amount of drainable pores and the stability ratio. The latter increased…

Modelling rainfall interarrival times and rainfall depths at daily scale

Analysis of daily rainfall data, and subsequent modelling of some derived variables concerning rainfall, is fundamental in different areas such as agricultural, ecological, and engineering disciplines. A way of studying the alternance of consecutive rainy days (wet spells) and no-rainy days (dry spells) is through the interarrival time (IT), which is the time elapsed between two consecutives rainy days. If we suppose that IT observations are independent and identically distributed (i.i.d.), ITs are usually modelled through a renewal processes. The simplest renewal process is the Bernoulli process with ITs geometrically distributed. The need to suppose a non-constant probability of rain brin…

Modeling the probability distribution of peak discharge for infiltrating hillslopes

Hillslope response plays a fundamental role in the prediction of peak discharge at the basin outlet. The peak discharge for the critical duration of rainfall and its probability distribution are needed for designing urban infrastructure facilities. This study derives the probability distribution, denoted as GABS model, by coupling three models: (1) the Green-Ampt model for computing infiltration, (2) the kinematic wave model for computing discharge hydrograph from the hillslope, and (3) the intensity-duration-frequency (IDF) model for computing design rainfall intensity. The Hortonian mechanism for runoff generation is employed for computing the surface runoff hydrograph. Since the antecede…

La formula razionale rivisitata

The Rational Formula (RF), also known as CIA formula, is probably the most applied equation in practical hydrology to compute the peak discharge, due to its simplicity and effective compromise between theory and data availability. The RF assumes the linearity of the hillslope response, neglects the time to ponding and the antecedent soil moisture condition (ASMC), concentrates the infiltration effect in the runoff coefficient (C) which estimation is highly controversial, since it is based on qualitative indications. This paper proposes an advanced rational formula that makes it possible to derive the peak discharge at the hillslope scale, where the above assumptions are relaxed and which de…

Determining Soil Hydraulic Properties Using Infiltrometer Techniques: An Assessment of Temporal Variability in a Long-Term Experiment under Minimum- and No-Tillage Soil Management

Conservation agriculture is increasingly accepted by farmers, but the modeling studies on agro-environmental processes that characterize these agricultural systems require accurate information on the temporal variability of the soil&rsquo

Modelling the Frequency of Interarrival Times and Rainfall Depths with the Poisson Hurwitz-Lerch Zeta Distribution

The Poisson-stopped sum of the Hurwitz&ndash;Lerch zeta distribution is proposed as a model for interarrival times and rainfall depths. Theoretical properties and characterizations are investigated in comparison with other two models implemented to perform the same task: the Hurwitz&ndash;Lerch zeta distribution and the one inflated Hurwitz&ndash;Lerch zeta distribution. Within this framework, the capability of these three distributions to fit the main statistical features of rainfall time series was tested on a dataset never previously considered in the literature and chosen in order to represent very different climates from the rainfall characteristics point of view. The results address t…

Spatial variability of dry spells duration statistical distributions

Dry spells duration and its extent in space, is a key factor in water resources problems. In order to modelling the empirical distribution of dry spells (DS) frequencies observed in Sicily (i.e. in a typical Mediterranean climate), Agnese et al. (2014) successfully applied the two-parameter polylogarithm-series distribution. Because of the strong seasonality characterising Sicily’s rainfall regime, statistical analysis was separately applied to two data sets, referred to as “dry” and “wet” seasons, respectively. In this work, a similar analysis was carried out for a set of 26 DS time-series recorded in a large area (about 30000 km2), including Piedmont and the Aosta Valley. Area altitude ra…

Simple flume for flow measurement in sloping open channel

First, this paper presents a new flume for measuring flow discharge in sloping channels, originally proposed by Samani and Magallanez for use in a horizontal channel. The flume is obtained by inserting two semicylinders in a rectangular cross section. Then, using dimensional analysis and the self-similarity theory, the stage-discharge relationship of the flume is theoretically deduced. For determining the two coefficients of the power stage-discharge equation, some experimental runs are carried out using flumes characterized by different values of the contraction ratio (ranging from 0.17 to 0.81) and of the flume slope (ranging from 0.5 to 3.5%). Finally, for a given range of the contractio…

Analytical approach extending the Granier method to radial sap flow patterns

Abstract The Granier thermal dissipation (TD) method is probably the most applied method to compute the transpiration flux of trees, due to its simplicity and effective compromise between theory and data availability. Starting from the heat transfer equations at the basis of Granier’s method, the objective of this paper is to derive an analytical solution for the transpiration flux to extend the sap flow equations to the radial domain. We adopted a flexible approach to cope with the differences in radial sapflow density (SFD) profile shapes that are known to occur in relation to wood anatomy (diffuse porous vs. ring- or non-porous xylem). With this purpose, we investigated the robustness of…

Dual-Diameter Laterals in Center-Pivot Irrigation System

Design strategies to enhance modern irrigation practices, reduce energy consumption, and improve water use efficiency and crop yields are fundamental for sustainability. Concerning Center-Pivot Irrigation Systems, different design procedures aimed at optimizing water use efficiency have been proposed. Recently, following a gradually decreasing sprinkler spacing along the pivot lateral with constant diameter and sprinkler flow rate, a new design method providing a uniform water application rate has been introduced. However, no suggestions were given to design multiple-diameter laterals characterized by different values of the inside pipe diameter. In this paper, first the previous design pro…

Effects of traditional forest management on carbon storage in a Mediterranean holm oak (Quercus ilex L.) coppice

Abstract: In the last decade, there has been increased interest in measuring and modeling storage in the five forest carbon pools: the aboveground and belowground biomass (living biomass), the deadwood and litter (dead biomass), and the soil (soil organic matter). In this paper, we examined carbon storage in a holm oak coppice stand in the Madonie Mountains in Sicily (Italy), which is a typical case of managed coppice stands. Today, traditional coppice practices are only applied to a small number of forested areas in Sicily, such as the selected site, because of the decline in demand for wood and charcoal. The dendrometric parameters of the stands were recorded, and silvicultural indices we…

Linking the Kinetic Energy Fraction and Equivalent Length Method for Trickle Irrigation Design under Local Losses

New methods using analytical relationships to design drip irrigation laterals and subunits have been introduced in recent years based on the assumption that minor losses can be neglected. This assumption could be relaxed by applying the equivalent method, which makes it possible to account for minor losses, such as those caused by emitter connections, through formulas based on the rationale that an equivalent length of the drip lateral produces the same losses. However, equivalent length formulas are empirical; thus, they do not necessarily cover the entire range of conditions in the real-world contexts in which the formulas will be applied, and their extrapolation could lead to erroneous r…

Improvement of FAO-56 Model to Estimate Transpiration Fluxes of Drought Tolerant Crops under Soil Water Deficit: Application for Olive Groves

[EN] Agro-hydrological models are considered an economic and simple tool for quantifying crop water requirements. In the last two decades, agro-hydrological physically based models have been developed to simulate mass and energy exchange processes in the soil-plant-atmosphere system. Although very reliable, because of the high number of required variables, simplified models have been proposed to quantify crop water consumes. The main aim of this paper is to propose an amendment of the Food and Agricultural Organization (FAO) of the United Nations FAO-56 spreadsheet program to introduce a more realistic shape of the stress function, valid for mature olive orchards (Olea europaea L.). The mod…

Una metodologia probabilistica semplificata di riproduzione del ruscellamento superficiale sul versante: possibili riscontri applicativi

Il lavoro presenta un modello semplificato per la riproduzione del reticolo di ruscellamento superficiale sul versante. Il modello richiede solo due parametri, il primo è legato alla capacità di produzione del deflusso del versante, nella condizione iniziale del processo, il secondo dipende dal grado di divagazione del reticolo. Tali parametri, in chiave idrologica, danno conto degli effetti che principalmente influenzano la risposta idrologica del versante: l’intensità di pioggia, la macroscabrezza e la pendenza del versante stesso. L’attendibilità del modello richiede, ovviamente, una validazione sperimentale che al momento è stata solo avviata.

Gravity-Driven Infiltration and Subsidence Phenomena in Posidonia oceanica Residues

A simplified infiltration model for highly permeable porous media was introduced, assuming the matric potential gradient as negligible compared to the gravitational gradient. This model enabled us to determine the delay time, i.e., the time that the water front takes (from the beginning of rainfall) to reach the bottom of the highly permeable layer. Posidonia oceanica (Linnaeus) Delile residues were used as a porous media, in order to study the infiltration process that provides salt leaching under natural rainfall when these residues are arranged in a storage area, before reusing. By using a laboratory rainfall simulator, delay times were measured to verify the applicability of the aforeme…

Analytical Solution of the Richards Equation under Gravity-Driven Infiltration and Constant Rainfall Intensity

In the field of soil hydrology, the Richards equation is commonly used to model water flow in unsaturated soils. The high nonlinearity of the Richards equation makes it very challenging to solve analytically for situations that are meaningful in practical applications. In this paper, an exact and simple analytical solution of the Richards equation under gravity-driven infiltration and constant rainfall intensity is derived. First, the solution is presented under Torricelli's law, which mimics the soil hydraulic conductivity function and describes the emptying or filling process of a nonlinear water reservoir. Then, following a similar approach, the solution is extended to the Brooks and Cor…

Analytical solution of kinematic wave time of concentration for overland flow under green-ampt infiltration

In this paper the well-known kinematic wave equation for computing the time of concentration for impervious surfaces has been extended to the case of pervious hillslopes, accounting for infiltration. An analytical solution for the time of concentration for overland flow on a rectangular plane surface is derived using the kinematic wave equation under the Green-Ampt infiltration. The relative time of concentration is defined as the ratio between the time of concentration of an infiltrating plane and the soil sorptivity time scale, depending on the normalized rainfall intensity and a parameter synthesizing the soil and hillslope characteristics. It is shown that for a more complex case (corre…

Effect of biochar on the physical and structural properties of a sandy soil

Abstract Biochar application to soil can be considered as a means to improve soil quality, thereby optimizing irrigation management and reducing irrigation needs, especially in dryland regions. This paper is aimed at investigating the effect of biochar (BC) on a desert sandy soil (Al Foah, United Arab Emirates) in terms of bulk density, porosity, water retention, plant available water (AWmax), aggregate stability (AS) and specific surface area (BET-SSA). BC was produced from forest biomass (Italy). Soil water retention was measured by the High Energy Moisture Characteristic (HEMC) and by pressure plate measurements, by using BC fractions equal to 0 (soil only), 0.014, 0.091, 0.23, 0.33 and …

SCS Curve Number and Green-Ampt Infiltration Models

Soil Conservation Service curve number (SCS-CN) and Green-Ampt (GA) infiltration models are probably the most applied equations in practical hydrology to compute the amount of direct runoff from rainfall. Both models are very simple, require few parameters, and present drawbacks and advantages. The empirical CN model concentrates the infiltration effect in the curve number and in the so-called soil hydrological groups, which have been widely characterized for different soil types, land cover, and antecedent soil moisture conditions (ASMCs), although the latter was considered ambiguous, whereas soil hydrological characteristics, including ASMC, are taken into account for the simplified physi…

Explicit relationships for optimal designing rectangular microirrigation units on uniform slopes: The IRRILAB software application

Abstract Many attempts have been made to provide easy tools for designing microirrigation units. However, most of these have dealt with numerical solutions, which require many trial-and-error attempts and time-consuming iterations, performed by applying the basic hydraulic equations from the manifold to the end of both the downhill and the uphill sides of the laterals. Recently, analytical procedures to optimally design paired drip laterals on uniform slopes were proposed, providing readily obtainable results and energy saving. Although these analytical solutions can be practically applied, they only make it possible to design a one-lateral unit; to be really interesting for practical appli…

Un modello di generazione e trasporto del deflusso: Applicazione a un piccolo bacino

Aridity index, soil erosion and climate drive no-till ecosystem services trade-off in Mediterranean arable land

Abstract Despite the relevant literature on the advantages of no-till (NT) management, the world area under NT is only 10% of the arable land, probably due to several limiting factors as climate, soil types, farming systems and yield. Soil conservation practices and particularly NT soil management are able to provide many ecosystem services (ESs). This paper suggests a framework to determine the area distribution of soil erosion control and food security ESs trade-offs furnished by NT, starting from the potential soil erosion and aridity index maps. The interaction between the potential soil erosion and the aridity index showed that different trade-offs and synergies of multiple ESs may occ…

Discussion of "Hydraulic Model of Transition of Transient to Steady Flows in the Vadose Zone" by Yaguo Zhang, Tonglu Li, Wei Shen, and Yu Wang

The authors wrote an interesting article dealing with a simple hydraulic model to illustrate the transition mechanism of transient to steady flows in the vadose zone. The soil behavior is described by a set of nine vertically aligned cylinders, each opened at the top and with a small outlet at the bottom. The water level dynamic of each cylinder, associated with an intermittent constant rainfall applied to the top cylinder, C0, was analyzed and numerical simulations were performed. The only objective of this discussion is to show that results similar to those proposed by the authors could be obtained by using the recently introduced Richards equation analytical solution, under gravity-drive…

Minor Losses and Best Manifold Position in the Optimal Design of Paired Sloped Drip Laterals

Centre-pivot irrigation system design for uniform water application rate

&amp;lt;p&amp;gt;In the last few decades, the use of centre-pivot irrigation systems has significantly increased, since it makes farming easier, is more efficient and less time-consuming compared to the other irrigation systems. Several studies have been focused on the hydraulics of the centre-pivot systems. Standard high-pressure impact sprinklers or low-pressure spray sprinklers or Low Energy Precision Application (LEPA) systems are generally mounted on the pipeline.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;To ensure the uniformity of water application, the centre-pivot design requires increasing the flow rates along the lateral, because the sprinklers farther from the pivot move faster, and th…

Tapered drip laterals and manifolds in flat and rectangular irrigation units

Multiple-diameter laterals and manifolds reduce the total cost in microirrigation systems, however, the length of each sublateral should be determined carefully to assure appropriate performance and uniformity of emitter flow rates. The most accurate method is numerical trial and error, which is time-consuming. Many research efforts have been made to propose simple analytical design procedures. By using the power-law form of the Darcy-Weisbach formula, and equal emitters spacing for the sublaterals, Sadeghi et al. (2016) extended a previously introduced design solution for one-diameter laterals to tapered laterals. Recently, a simplified procedure to design dual-diameter drip laterals has b…

Durum wheat yield uncertainty under different tillage management practices and climatic conditions

Abstract In the field of conservative agriculture, no-till (NT) management has been receiving increasing interest, with 45 million ha of land under no-till management in 1999 to 155 million ha in 2014. Up until now, no-till has only been observed to perform better under rainfed conditions, especially in dry climates mainly because the reduced tillage system retains more soil moisture. However, the adoption of alternative agricultural practices (NT) can be improved only if uncertain and consequent assumption of risk is well known and accepted. For these reasons, the aim of this research is (i) to define durum wheat suitability under NT soil management in terms of yield success probability an…

Modelling wet and dry spells for daily rainfall data series: an application to irrigation management in North-West Italy

Rainfall time variability is relevant for agricultural production. The daily time scale is often used in modelling crop and soil water balance. In this work a novel statistical analysis of wet and dry spells is presented, together with an application in an Italian area characterised by a relevant climate spatial variability, due to the presence of both high mountains (e.g.: Mont Blanc) and of the Mediterranean Sea. Statistical analysis of the sequences of rainy days, wet spells (WS), and that of no-rainy days, dry spells (DS), could be carried out separately (as widely applied in the past) or jointly, by introducing the inter-arrival time (IT), representing the time elapsed between two subs…

Minor Losses and Best Manifold Position in the Optimal Design of Paired Sloped Drip Laterals

Arranging paired laterals so that two distribution pipes extend in opposite directions from a common manifold contributes to providing more uniform pressure to all laterals in the system, increasing water use and energy efficiency of micro-irrigation. Towards this end, by neglecting emitters’ minor losses, analytical procedures to design paired drip laterals laid on uniform slopes were introduced. More recently, it was shown that for an optimal paired sloped lateral design the best position of the manifold (BMP) equals 24%. In this paper, first the mentioned analytical procedure is extended to the case in which minor losses are considered. Second, by neglecting minor losses, a comparison in…

Distribuzione di probabilità della portata di piena a scala di versante generata da deflusso hortoniano

Modeling the probability distribution of peak discharge for infiltrating hillslopes

Hillslope response plays a fundamental role in the prediction of peak discharge at the basin outlet. The peak discharge for the critical duration of rainfall and its probability distribution are needed for designing urban infrastructure facilities. This study derives the probability distribution, denoted as GABS model, by coupling three models: (1) the Green-Ampt model for computing infiltration, (2) the kinematic wave model for computing discharge hydrograph from the hillslope, and (3) the intensity-duration-frequency (IDF) model for computing design rainfall intensity. The Hortonian mechanism for runoff generation is employed for computing the surface runoff hydrograph. Since the antecede…

Indagine sperimentale su un semplice misuratore di portata per correnti a pelo libero su fondo inclinato

Maximizing water use efficiency in designing microirrigation unit (IrriLab Software)

As the year 2050 approaches, the world population will reach 9 billion - so does the challenge of doubling crop yields. To meet this crop yields demand, the associated dramatic improving of water productivity (WP) must necessarily be accompanied by maximization of water use efficiency (WUE) (Ragab 2011, UNEP 2014). In this work, a recently developed software (IrriLab, https://www.facebook.com/irrilab) moving in this direction is presented. IrriLab is a very simple toll allows to design microirrigation unit optimizing WUE, pressure energy and irrigation unit costs. Irrigation software available in commerce provide microirrigation system designs, by mainly looking at the maximum flow rate uni…

I servizi ecosistemici forestali connessi alla tutela del suolo e delle acque

Valutazione delle resistenze al moto di una corrente su un fondo granulare eterogeneo

Trend of inter-arrival times of rainfall events for Italian Sub-Alpine and Mediterranean areas

An Innovative Soil Bioengineering Technique by Waste Materials: The RiVite Project

This paper describes the RiVite project granted by the Italian Ministry of Economic Development according to the JUMP (Joint Universities Program for PoC) program for patents enhancement, proposed by Sant’Anna School, Scuola Normale and the University of Palermo. The patent (Calvo, R., D’Asaro, F., Baiamonte, G.: Metodo per la realizzazione di un’opera costruttiva modulare per la protezione del territorio e detta opera. Attestato di Brevetto per Invenzione Industriale, n° 102,017,000,141,369, Ministero dello Sviluppo Economico, Roma, 27/02/2020.) consists of an advanced soil bioengineering work providing anti-erosion function, consolidating and stabilizing of slopes, thus for land protectio…

Biochar amended soils and water systems: Investigation of physical and structural properties

There are significant regional differences in the perception of the problems posed by global warming, water/food availability and waste treatment recycling procedures. The study illustrates the effect of application of a biochar (BC) from forest biomass waste, at a selected application rate, on water retention, plant available water (PAW), and structural properties of differently standard textured soils, classified as loamy sand, loam and clay. The results showed that soil water retention, PAW, and aggregate stability were significantly improved by BC application in the loamy sand, confirming that application of BC to this soil was certainly beneficial and increased the amount of macropores…

Plant and soil responses to deficit and saline irrigation under field irrigated conditions in a sicilian vineyard

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 prelimi…

Probability distribution of peak discharge at hillslope scale derived by an eco-hydrological approach

A comparison between the single ring pressure infiltrometer and simplified falling head techniques

Testing the relative performances of the single ring pressure infiltrometer (PI) and simplified falling head (SFH) techniques to determine the field saturated soil hydraulic conductivity, Kfs, at the near point scale may help to better establish the usability of these techniques for interpreting and simulating hydrological processes. A sampling of 10 Sicilian sites showed that the measured Kfs was generally higher with the SFH technique than the PI one, with statistically significant differences by a factor varying from 3 to 192, depending on the site. A short experiment with the SFH technique yielded higher Kfs values because a longer experiment with the PI probably promoted short-term swe…

Determining Probability Distribution of Hillslope Peak Discharge by Using an Analytical Solution of Kinematic Wave Time of Concentration.

Hillslope hydrology is fundamental for understanding the flood phenomenon and for evaluating the time of concentration. The latter is a key variable for predicting peak discharge at the basin outlet and for designing urban infrastructure facilities. There have been a multitude of studies on the hydrologic response at the hillslope scale, and the time of concentration has been derived for different approaches. One approach for deriving hillslope response utilizes, in a distributed form, the differential equations of unsteady overland flow, specifically developed at the hydrodynamic scale, in order to account for the spatial heterogeneity of soil characteristics, topography, roughness and veg…

Trends of some high quantiles of average and extremes inter-arrival timesand rainfall depths at daily scale for an Italian Sub-Alpine area

Modeling of rainfall statistical structure represents an important research area in hydrology, meteorology, atmospheric physics and climatology, because of the several theoretical and practical implications. The statistical inference of the alternation of wet periods (WP) and dry periods (DP) in daily rainfall records can be achieved through the modelling of inter-arrival time-series (IT), defined as the succession of times elapsed from a rainy day and the one immediately preceding it. It has been shown previously that the statistical structure of IT can be well described by the 3-parameter Lerch distribution (Lch). In this work, Lch was successfully applied to IT data belonging to a sub-al…

Measuring and Modelling Evaporation Losses from Wet Branches of Lemon Trees

Evaporation losses of rainfall intercepted by canopies depend on many factors, including the temporal scale of observations. At the event scale, interception is a few millimetres, whereas at a larger temporal scale, the number of times that a canopy is filled by rainfall and then depleted can make the interception an important fraction of the rainfall depth. Recently, a simplified interception/evaporation model has been proposed, which considers a modified Merrian model to compute interception during wet spells and a simple power-law equation to model evaporation from wet canopy during dry spells. Modelling evaporation process at the sub hourly temporal scale required the two parameters of …

Modelling the frequency distribution of inter-arrival times from daily precipitation time-series in North-West Italy

Abstract The discrete three-parameter Lerch distribution is used to analyse the frequency distribution of inter-arrival times derived from 26 daily precipitation time-series, collected by stations located throughout a 28,000 km2 area in North-West Italy (altitudes ranging from 113 m to 2,170 m a.s.l.). The precipitation regime of these Alpine regions is very different (latitude 44.5 to 46.5 N) from the typical Mediterranean precipitation regime of the island of Sicily (latitude 37 to 38 N), where the Lerch distribution has already been tested and whose results are compared. In order to verify the homogeneity of the precipitation time series, the Pettitt test was preliminarily performed. In …

Complex Rating Curves for Sharp Crested Orifices and Rectangular or Triangular Weirs under Unsteady Flow Conditions

The importance of discharge measurements is fully acknowledged in many research fields, mostly in hydrology. Numerous measurement devices and various overflow structures have been proposed for discharge measurements; however, their use is based on calibrated simple stage discharge relationships that may cause significant errors when unsteady flow conditions occur. This issue is quite common because of rainfall and runoff temporal variability that inhibits the achievement of the steady state. Although this issue has already been experimentally investigated, it seems that a physically based line of approach has not been attempted before. In this paper, unsteady stage discharge relationships o…

Sul tempo di risposta di un versante a prevalente deflusso hortoniano

La distinzione del bacino idrografico in versanti e reticolo attiene ai differenti processi che in essi specificamente hanno luogo. In particolare i versanti sono sede dei fenomeni diffusi di formazione del deflusso superficiale e di erosione idrica, mentre la rete è sede dei fenomeni concentrati di trasporto del deflusso liquido e solido sino alla sezione di chiusura del bacino. Nell’ipotesi che la formazione prevalente del deflusso superficiale avvenga secondo lo schema hortoniano, tipico dei versanti privi di vegetazione, nel presente lavoro è suggerita una metodologia, applicabile anche ad altre modalità di formazione, per la valutazione del tempo caratteristico di risposta del versante…

A model of dunnian flow at hillslope scale

The development of a thin stream above the soil surface (overland flow) is associated to two mechanism of runoff generation on the hillslope: the infiltration excess (hortonian flow) and saturation excess (dunnian flow) mechanism. The first one is typical of arid and semi-arid regions, usually characterised by high rainfall intensities on soil exhibiting low permeability. The second one, firstly introduced by Hewlett and Hibbert, constitutes the main mechanism of runoff generation in humid regions, characterised by high groundwater table. In the last mechanism runoff is produced by contributing areas of restricted extent that expands with time, where near to the bottom of the hillslope a hi…

Empirical methods to determine average annual runoff coefficient in Sicilian basins

Statistical analysis of inter-arrival times of rainfall events for Italian Sub-Alpine and Mediterranean areas

Abstract. In this work a set of time-series of inter-arrival times of rainfall events, at daily scale, was analysed, with the aim to verify the issue of increasing duration of dry periods. The set consists of 12 time-series recorded at rain gauges in 1926–2005, six of them belong to an Italian Sub-Alpine area (Piedmont) and six to a Mediterranean one (Sicily). In order to overcome the problem related to limited sample size for high values of inter-arrival times, the discrete probability polylog-series distribution was used to fit the empirical data from partial (20 yr) time-series. Moreover, a simple qualitative trend analysis was applied to some high quantiles of inter-arrival times as wel…

Runoff coefficients to predict peak discharge at hillslope scale: A small contribution to theoretical hydrology

The science of hydrology holds a central role in the field of environmental Earth science, being intimately connected to meteorology, climatology, hydrogeology and ecology. In particular, the knowledge of hillslope hydrology is fundamental for understanding the flood phenomenon, for predicting the peak discharge and its probability distribution, which is necessary in many practical applications (design of hydraulic structures, urban, extra-urban planning, etc.). Using different approaches, there have been a multitude of studies on the hydrologic response at hillslope scale. One approach for deriving the hillslope response utilizes, in a distributed form, the differential equations of unstea…

Simple Relationships for the Optimal Design of Paired Drip Laterals on Uniform Slopes

Microirrigation plants, if properly designed, allow water use efficiency to be optimized and quite high values of emission uniformity to be obtained in the field. It is known that disposing paired laterals, in which two distribution pipes extend in opposite directions from a common manifold, contribute to increasing water use efficiency. Recently, an analytical procedure has been proposed to optimally design paired drip laterals on uniform slopes under the assumption of neglect: (1) the variations of the emitters’ flow rate along the lateral, and (2) the local losses due to the emitters’ insertions. However, this procedure is not readily usable for every geometric and hydraulic characterist…

IL SOFTWARE IRRILAB PER GLI IMPIANTI MICROIRRIGUI: VERIFICHE NUMERICHE E SPERIMENTALI

Nell’ambito delle attività di ricerca condotte presso il Dipartimento di Scienze Agrarie, Alimentari e Forestali dell’Università di Palermo è stato di recente messo a punto un nuovo metodo di calcolo ottimale delle ali gocciolanti, usate nella mi-croirrigazione, attualmente patent pending (“Metodo speditivo per il dimensiona-mento di ali gocciolanti in pendenza”, Università deli Studi di Palermo, Ministero dello Sviluppo Economico - Ufficio Italiano Brevetti e Marchi). Il metodo è stato successivamente esteso ai settori microirrigui, di forma rettangolare e comunque inclinati, in un software applicativo, denominato IrriLab. L’obiettivo del lavoro è quello di “testare” il funzionamento del s…

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

In 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 de…

Applying a probabilistic model of rainfall and snow days occurrence to daily series recorded in NW Italy.

Daily precipitation records exist spanning several decades. A valuable amount of climatic information exists in the time-series of interarrival times (IT), defined as the succession of times (number of days) elapsed from a rainy (or snowy) day to the one immediately preceding it.In a previous work, Agnese et al. (2014) have been successfully tested some probabilistic modelling of rain occurrence on Sicily rainfall data; particularly, the better fitting of IT’s observed frequencies was obtained by 3-parameter Lerch-series distribution. In this work thisdistribution is tested on 70 years of 20 precipitation time-series taken in the North-West Italy, both in the plain and in the mountains, up …

Overland Flow Times of Concentration for Hillslopes of Complex Topography

The time of concentration is an important parameter for predicting peak discharge at the basin outlet and for designing urban infrastructure facilities. In studying the hillslope response, employing hydraulic equations of flow, the shape of the hillslope geometry has often been assumed as rectangular and planar. However, natural hillslopes have complex topographies whose shapes are characterized by irregularly spaced contour lines. Recently, kinematic wave time of concentration has been derived for rectangular and curved parallel hillslopes. This paper extends this work to hillslopes of complex planform geometry, considering the degree of divergence or convergence of the hillslope. The exte…

Modelling the occurrence of rainy days under a typical Mediterranean climate

The statistical inference of the alternation of wet and dry periods in daily rainfall records can be achieved through the modelling of inter-arrival time-series, IT, defined as the succession of times elapsed from a rainy day and the one immediately preceding it. In this paper, under the hypothesis that ITs are independent and identically distributed random variables, a modelling framework based on a generalisation of the commonly adopted Bernoulli process is introduced. Within this framework, the capability of three discrete distributions, belonging to the Hurwitz–Lerch-Zeta family, to reproduce the main statistical features of IT time-series was tested. These distributions namely Lerch-se…

Sperimentazione di laboratorio sulle soglie in massi

Verification of IRRILAB Software Application for the Hydraulic Design of a Micro-Irrigation System by Using IRRIPRO for an Apple Farm in Sicily

In recent years, many studies have been performed to develop simple and accurate methods to design micro-irrigation systems. However, most of these studies are based on numerical solutions that require a high number of iterations and attempts, without ensuring to maximize water use efficiency and energy-saving. Recently, the IRRILAB software, which is based on an analytical approach to optimally design rectangular micro-irrigation units, has been developed, providing the solution corresponding to the maximum energy-saving condition, for any slope of the laterals and of the manifold. One IRRILAB limitation is that, according to its theoretical basis, the rectangular planform geometry and uni…

Coupling overland and subsurface flow model at hillslope scale

Discussion of “Analysis of Geometrical Relationships and Friction Losses in Small-Diameter Lay-Flat Polyethylene Pipes” by Giuseppe Provenzano, Vincenzo Alagna, Dario Autovino, Juan Manzano Juarez, and Giovanni Rallo

For a lay-flat drip line with an inner nominal diameter dn = 16 mm, characterized by three different pipe wall thicknesses, WT, 6, 8 and 10 mil, the Authors of the original paper very accurately investigated the geometrical expansion of the cross-sectional diameter as a function of different pressure head values, ranging in between 0.84-17.55 m. Results obtained by the Authors, for pressure heads not exceeding a threshold pressure value, showed significant d variations, in a very narrow range of pressure heads, which however is seldom considered in practice (less than 3 m). The Authors experimentally evaluated a modified Blasius’ law friction coefficient, c, equal to 0.285, corresponding to…

A comparison between the single ring pressure infiltrometer and simplified falling head techniques

Testing the relative performances of the single ring pressure infiltrometer (PI) and simplified falling head (SFH) techniques to determine the field saturated soil hydraulic conductivity, Kfs, at the near point scale may help to better establish the usability of these techniques for interpreting and simulating hydrological processes. A sampling of 10 Sicilian sites showed that the measured Kfs was generally higher with the SFH technique than the PI one, with statistically significant differences by a factor varying from 3 to 192, depending on the site. A short experiment with the SFH technique yielded higher Kfs values because a longer experiment with the PI probably promoted short-term swe…

Simplified Model to Predict Runoff Generation Time for Well-Drained and Vegetated Soils

The study of generation process of subsurface stormflow, typical of well-drained and high permeable soils, can be theoretically carried out by applying the continuity and the motion equations with the appropriate boundary conditions. However, difficulties and uncertainness on determining soil hydraulic properties and soil physics heterogeneities let this way not always feasible. In a different way, processes dynamic can be derived by the local scale through a coarse graining procedure, allowing to preserve medium motion character, while hydraulic fluctuation of the motion are lost. Following an approach as this, in this paper a simplified model to predict the runoff generation time, the so-…

Il misuratore di portata a cilindri (BF): indagine sperimentale e verifica di campo

Assessing the influence of different biochar fractions on soil structure and soil water retention: laboratory investigation on a Sicilian soil

AN ANALYTICAL SOLUTION OF KINEMATIC WAVE EQUATIONS FOR OVERLAND FLOW UNDER GREEN-AMPT INFILTRATION

This paper deals with the analytical solution of kinematic wave equations for overland flow occurring in an infiltrating hillslope. The infiltration process is described by the Green-Ampt model. The solution is derived only for the case of an intermediate flow regime between laminar and turbulent ones. A transitional regime can be considered a reliable flow condition when, to the laminar overland flow, is also associated the effect of the additional resistance due to raindrop impact. With reference to the simple case of an impervious hillslope, a comparison was carried out between the present solution and the non-linear storage model. Some applications of the present solution were performed…

Agricultural landscapes and biodiversity conservation: a case study in Sicily (Italy)

The diversity of life is made up not only of the diversity of plants and animal species, habitats and ecosystems, but also of the diversity of human cultures. These diversities interact with one another in complex ways and express the mutual adaptation between humans and the environment at local level. Sicilian traditional agro-ecosystems, due to the history of the territory and the resulting social and economic context, are configured in a heterogeneous mosaic rich in residual features of environmental value, which enhance the connectivity of the ecological network and support a high proportion of species that are rare or of conservation concern. As a case study we analyzed the characteris…

Revisiting the Solid Flux Theory

Several variations of the basic activated sludge process and of the related design procedures for final clarifiers have been developed, which are frequently based on the well-known solid flux theory (SFT). In this paper, by using the Lambert W function and a &ldquo;virtual&rdquo; solid flux corresponding to the Vesilind parameters&rsquo; ratio, the SFT is reformulated, and dimensionless groups are detected, which highly reduce the number of parameters that are involved in the final clarifiers&rsquo; design procedure. The derived dimensionless relationships and the corresponding plots have general validity since they can be applied to all the possible design/verification parameter combinatio…

Comparison between Curve Number empirical values and Curve Number obtained by handbook tables at basin scale in Sicily, Italy

Dimensionless Stage-Discharge Relationship for a Non-Linear Water Reservoir: Theory and Experiments

In the field of hydrology, stage&ndash

Hydraulic Design of the Center-Pivot Irrigation System for Gradually Decreasing Sprinkler Spacing

Design strategies that enhance modern irrigation practices, reduce energy consumption, and improve water use efficiency and crop yields are fundamental for sustainability. Although microirrigation is currently a widely applied method, center-pivot irrigation systems have become very popular on large farms, thanks to their automation, wide-coverage, and reliability. Different design procedures have been proposed, even though some aspects have not been solved yet. This paper presents a simple design procedure for center-pivot systems using a gradually decreasing sprinkler spacing along with a pivot lateral, which makes it possible to set favorable and uniformly distributed water application r…

Time Scale Effects and Interactions of Rainfall Erosivity and Cover Management Factors on Vineyard Soil Loss Erosion in the Semi-Arid Area of Southern Sicily

Several authors describe the effectiveness of cover crop management practice as an important tool to prevent soil erosion, but at the same time, they stress on the high soil loss variability due to the interaction of several factors characterized by large uncertainty. In this paper the Revised Universal Soil Loss Equation (RUSLE) model is applied to two Sicilian vineyards that are characterized by different topographic factors