Search results for "HVA"
showing 10 items of 78 documents
Soil erosion after land abandonment in a semiarid environment of southeastern Spain
1997
Different soil units were selected in southeastern Spain to investigate the effects of land abandonment on soil erosion under semiarid conditions. The study sites selected were a cultivated field (bare), a 3‐yr‐abandoned field (herbs), a 10‐yr‐abandoned field (Artemisia herba‐alba Asso.), and two soil units covered with semi‐native (Stipa tena‐cissima L) and native (Pinus halepensis Miller) vegetation. Simulated rainfall measurements showed that the erosion and runoff increased after the land abandonment, but later erosion decreased owing to the influence of increasing vegetation. Runoff discharge (35%) and the erosion rates (334 g m2 h‐1) were high in the 3‐yr‐abandoned land in comparison …
The influence of geomorphological position and vegetation cover on the erosional and hydrological processes on a Mediterranean hillslope
1998
Soil erosion and runoff rates are assumed to be highly dependent on slope position. However, little knowledge exists about the hydrogeomorphological processes at the pedon scale that support this idea. In order to assess the hydrological and erosional behaviour of soils at different slope positions, simulated rainfall experiments (55 mm was applied during one hour) were carried out on a south-facing slope with underlying limestone in south-east Spain. In the mean terms, the erosion rates (9 g m2 hr−1) and the runoff coefficients (12%) were very low at the scale of measurement (0·25 m2). The slope position does not affect erosion rates when the measurements are carried out under extreme dry …
Soil hydraulic properties determined by infiltration experiments and different heights of water pouring
2014
Abstract Establishing the dependence of the soil hydraulic characterization carried out by an infiltration experiment on the procedure used to apply water on the confined soil surface may help to better interpret the collected data and also to develop more accurate strategies for soil hydraulic characterization. Soil was sampled at four Sicilian sites with both the Simplified Falling Head (SFH) technique and the Beerkan Estimation of Soil Transfer parameters (BEST) procedure and two heights of water application (0.03 and 1.5 m). The most appropriate BEST algorithm to analyze the data was determined and the effect of the height of water pouring on the measured soil hydraulic properties was e…
Soil hydrological response under simulated rainfall in the Dehesa land system (Extremadura, SW Spain) under drought conditions
1998
Soil hydrology was investigated in the Guadelperalon experimental watershed in order to determine the influence of land use and vegetation cover on runoff and infiltration within the Dehesa land system. Five soil–vegetation units were selected: (1) tree cover, (2) sheep trials, (3) shrub cover, (4) hillslope grass and (5) bottom grass. The results of the simulated rainfall experiments performed at an intensity of 56·6 mm h−1 during one hour on plots of 0·25 m2, and the water drop penetration time test indicate the importance of water repellency in the Dehesa land system under drought conditions. Low infiltration rates (c. 9–44 mm h−1) were found everywhere except at shrub sites and in areas…
Hydrological and hydraulic behaviour of a surface flow constructed wetland treating agricultural drainage water in northern Italy.
2020
Abstract A surface flow constructed wetland (SFCW) treating agricultural drainage water was investigated with the aim to detect modifications in hydrological and hydraulic characteristics after more than a decade of operation. Ponded infiltration tests were conducted to estimate the saturated hydraulic conductivity, Ks, of the surface soil layer at the point scale. At the global scale, infiltration rate, i, was computed from the water balance to detect leakages from the pervious wetland surface. Tracer tests were conducted to analyse the existence of preferential flow inside the system and to estimate its hydraulic retention time (HRT). Clogging phenomena occurred given a mean Ks value of 3…
The effect of patchy distribution ofStipa tenacissimaL. on runoff and erosion
1997
In south-east Spain, a semi-arid area,Stipa tenacissima(alphagrass) covers large natural and semi-natural areas with a mosaic of tussocks and bare zones. However, little knowledge exists about the influence of these patterns on runoff and erosion. In order to understand the hydrological and erosional behaviour of the vegetated (herbs andalphagrass) and bare zones, rainfall simulation experiments were carried out at three sites in south-east Spain. The experiments showed that surface runoff and erosion is negligible in the tussock and quite high in the bare areas. High infiltration rates and deep wetting fronts were measured in the vegetated patches, and lower infiltration rates and shallowe…
Analysis of the new submarine interconnection system between Italy and Malta: Simulation of transmission network operation
2016
In this paper, some simulations of the interconnected Sicilian and Maltese transmission systems are performed, in order to assess this new system configuration. The HVAC submarine interconnection between Italy and Malta came into operation in 2015 and is part of a European programme for transmission grid interconnection improvement. This new line has been built in order to allow a better management of the power system of both the islands. Firstly, a brief description of the interconnection system is given. Moreover, the transmission systems of Sicily and Malta are depicted and their structures are shown. The simulations are carried out by means of a model of the interconnected system create…
Experiences, reputation, references and decision-making in an online hospitality network
2014
The aim of this thesis was to analyse behavioural patterns that occur after a negative experience during a hospitality exchange. The focus of this study is the largest online hospitality network to date, the CouchSurfing Project. CouchSurfing enables travellers to connect and to offer each other help in form of a free hospitality exchange. Furthermore, CouchSurfing presents a platform for cultural exchange and the possibility for members to connect in this online-offline community. As part of a qualitative study, a voluntary online questionnaire has been distributed and answered by 35 CouchSurfing members. The results give insight of how they deal with a negative experience after offline in…
Na przedpolach Kamieńca Podolskiego. Zdławienie konfederacji barskiej na Podolu w świetle raportów Jana de Witte
2018
W artykule przedstawiona została sytuacja strategiczna twierdzy Kamieniec Podolski w okresie od zimy 1768 r. do zimy 1769 r., gdy na Podolu trwała konfederacja barska. Komendant twierdzy Józef de Witte dokładał wszelkich starań, aby utrzymać twierdzę, a przede wszystkim stanowiących jej garnizon żołnierzy w jak najlepszej kondycji, a przy tym dochować wierności królowi Stanisławowi Augustowi. Z zachowanych w Archiwum Narodowym w Krakowie raportów J. Witte do króla, Komisji Wojskowej oraz wysokich urzędników i dowódców wojska koronnego wynika, że w pełni mu się to udało. Raporty Wittego są przy tym cennym źródłem do zbadania procesu zdławienia przez wojska rosyjskie konfederacji barskiej na …
Field and Numerical Tests of the Two-Ponding Depth Procedure for Analysis of Single-Ring Pressure Infiltrometer Data
2013
Abstract The two-ponding depth (TPD) analysis procedure of single-ring infiltrometer data can yield invalid results, i.e., negative values of the field-saturated soil hydraulic conductivity or the matric flux potential, denoting failure of the two-level run. The objective of this study was to test the performance of the TPD procedure in analyzing the single-ring infiltrometer data of different types of soils. A field investigation carried out in western Sicily, Italy, yielded higher failure rates (40%) in two clay loam soils than in a sandy loam soil (25%). A similar result, i.e., fine-textured soils yielding higher failure rates than the coarse-textured one, was obtained using numerically …