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51.
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Building damage assessment after the 2009 Abruzzi earthquake 总被引:2,自引:2,他引:0
53.
The impact of a single hydropeaking event was studied in the Alpine stream Noce Bianco. Four stations were selected, one upstream and three, respectively, at 0.25, 6, and 8 km downstream from a hydropower plant. We collected drifting invertebrates during a planned water release that increased the discharge 7-fold. At the onset of the hydropeaking wave the number of invertebrates lost from the riverbed per minute to the drift increased 9-fold at the first downstream station and the same effects propagated 8 km downstream. The drift was composed mainly of aquatic insect larvae (Chironomidae, Plecoptera, Ephemeroptera Baetidae, and Psychodidae, with Chironomidae as the most abundant taxon at all stations) and partly by larval and adult riparian insects, and by Oligochaeta, which were particularly abundant at the station 6 km downstream. We monitored drift for 30 min from the start of the water release: peaks in drifting invertebrates occurred within 5–10 min of the beginning of the hydropeaking wave, and most of the invertebrates were washed out within the first 15 min of the water release. The different timeframes were possibly due to habitat preferences (most of the taxa that increased in the drift at the arrival of the wave were associated with algae and organic debris, which were washed off quickly by the increase in discharge) and/or behavioral adaptations (other taxa initially resisted the shear stress and began to drift with a delay of 5–10 min). The temporal pattern and drift composition corresponded well with those reported in literature, and indicate that repeated high-flow events of similar magnitude cause considerable losses from benthic populations to drift. 相似文献
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Modeling water resources of a highly irrigated alluvial plain (Italy): calibrating soil and groundwater models 总被引:1,自引:0,他引:1
Chiara Vassena Michele Rienzner Giansilvio Ponzini Mauro Giudici Claudio Gandolfi Cinzia Durante Davide Agostani 《Hydrogeology Journal》2012,20(3):449-467
Modern and effective water management in large alluvial plains that have intensive agricultural activity requires the integrated modeling of soil and groundwater. The models should be complex enough to properly simulate several, often non-linear, processes, but simple enough to be effectively calibrated with the available data. An operative, practical approach to calibration is proposed, based on three main aspects. First, the coupling of two models built on well-validated algorithms, to simulate (1) the irrigation system and the soil water balance in the unsaturated zone and (2) the groundwater flow. Second, the solution of the inverse problem of groundwater hydrology with the comparison model method to calibrate the model. Third, the use of appropriate criteria and cross-checks (comparison of the calibration results and of the model outputs with hydraulic and hydrogeological data) to choose the final parameter sets that warrant the physical coherence of the model. The approach has been tested by application to a large and intensively irrigated alluvial basin in northern Italy. 相似文献
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Tiziana Di Lorenzo Mauro Brilli Dina Del Tosto Diana M. P. Galassi Marco Petitta 《Environmental Earth Sciences》2012,67(8):2383-2398
The aim of this study is to apply an integrated approach to determine nitrate sources and fate in the alluvial aquifer of the River Vibrata (Abruzzi, central Italy) by coupling the Isotope and the Component approaches. Collected data include concentration and nitrogen isotope composition of groundwater samples from the alluvial aquifer and nitrogen loads arising from agricultural and non-agricultural sources. The adopted methodology identified synthetic fertilizers as main sources of nitrate in the Vibrata alluvial aquifer. At the catchment scale, two different zones have been identified: the Upper Valley, where infiltration to groundwater is dominant and nitrogen easily migrates into the aquifer; in this area, nitrate content in groundwater is stable and normally higher than EU requirements. Moreover, streamwaters are fed by groundwater with a nitrate content likely lowered by denitrification processes occurring in the hyporheic zone. In the Lower Valley, runoff processes dominate and the nitrate content in surface waters is higher. Nevertheless, groundwater is locally affected by denitrification that breaks down the nitrate content, which often reaches values consistent with law limits. 相似文献
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Mauro Giudici Stefano Margiotta Fiorella Mazzone Sergio Negri Chiara Vassena 《Environmental Earth Sciences》2012,67(7):1891-1907
The control exerted by the hydrostratigraphic structure on aquifer recharge, groundwater flow and discharge along the coastal areas of a Mediterranean basin (Salento peninsula, about 5,000?km2 wide, southern Italy) is assessed through the development and application of a groundwater flow model based on the reconstruction of the hydrostratigraphic architecture at the regional scale. The hydrostratigraphic model, obtained by processing surface and subsurface data, is applied to map the top of the main aquifer, which is hosted in the deep hydrostratigraphic unit corresponding to Cretaceous and Oligocene limestones with complex geometrical relationships with the sea. It is also used to estimate the aquifer recharge, which occurs by percolation through overlying younger sediments with low permeability. These data are completed with information about the soil use to estimate water abstraction for irrigation and with literature data to estimate the water abstraction for drinking and industrial purposes. The above-sketched conceptual model is the basis for a finite difference groundwater 2D pseudo-stationary flow model, which assumes the following fundamental approximations: the fractured and karst limestone hydrostratigraphic unit can be approximated, at the model scale, as a continuous medium for which the discrete Darcy??s law is valid; the transition zone between salt and fresh water is so small with respect to the grid spacing that the Ghyben?CHerzberg??s approximation for a sharp interface can be applied. Along the coastline different boundary conditions are assigned if the top of the limestone hydrostratigraphic unit lies either above the sea level (the aquifer has a free surface and fresh water is drained), or below the sea level (the aquifer is under pressure and the contact with sea occurs off-shore). The groundwater flow model correctly predicts the areas where the aquifer is fully saturated with salt water. 相似文献
60.
Giuliani S Piazza R Bellucci LG Cu NH Vecchiato M Romano S Mugnai C Nhon DH Frignani M 《Marine pollution bulletin》2011,62(5):1013-1024
PCBs were analysed in surficial sediments and selected sediment cores collected between 2002 and 2008 in Central Vietnam coastal lagoons. The aim was to determine contamination levels and trends, and to evaluate the effects of anthropogenic pressures and natural events. Samples were mostly fine-grained with low total PCB concentrations (0.367-44.7 μg kg−1). Atmospheric transport and post depositional processes modify to some degree the fingerprint of PCB inputs to the environment favouring the predominance of 3, 4 and 5 chlorinated congeners. The similarity of congener distributions in contemporary surficial samples also suggests the presence of a unique source over the entire study area, probably connected to mobilisation and long range transports from land-based stocks. The removal of consistent sediment layers is hypothesised based on repeated samplings of the same area. Natural meteorological events (such as typhoons) are suspected to be responsible for these sediment losses. 相似文献