The water balance of an Amazonian micro‐catchment: the effect of interannual variability of rainfall on hydrological behaviour

In humid tropical systems, the large intraseasonal and interannual variability of rainfall can significantly affect all components of the water balance. This variability and the lack of detailed hydrological and meteorological data in both temporal and spatial scales have created uncertainties regarding the closure of the water balance for the Amazon basin. Previous studies in Amazonian micro‐catchments suggested that both the unsaturated and groundwater system, which are not taken into consideration in basin‐wide water budgets published in the literature, play an important role in controlling the timing of runoff generation. In this paper, the components of the water balance and the variations in different storages within the system were examined using 3 years' data from a 6·58 km² micro‐catchment in central Amazonia. The role and relative importance of the various stores were examined. The results show a strong memory effect in the groundwater system that carries over seasonal climate anomalies from one year to the next and affects the hydrological response well beyond the time span of the anomaly. In addition, the deep unsaturated zone was found to play a key role in reducing most of the intraseasonal variability and also affected the groundwater recharge. This memory effect is crucial for sustaining streamflow and evaporation in years with rainfall deficiency. The memory effect caused by storage in the groundwater and unsaturated systems may also prevent the closure of annual large‐scale water balances, which assume that storage returns to a standard state each year. Copyright © 2007 John Wiley & Sons, Ltd.     

Relating Hyperspectral Airborne Data to Ground Measurements in a Complex and Discontinuous Canopy

The work described in this paper is aimed at validating hyperspectral airborne reflectance data collected during the Regional Experiments For Land-atmosphere EXchanges (REFLEX) campaign. Ground reflectance data measured in a vineyard were compared with airborne reflectance data. A sampling strategy and subsequent ground data processing had to be devised so as to capture a representative spectral sample of this complex crop. A linear model between airborne and ground data was tried and statistically tested. Results reveal a sound correspondence between ground and airborne reflectance data (R2 > 0.97), validating the atmospheric correction of the latter.     

An Excel Macro to Plot the HFE‐Diagram to Identify Sea Water Intrusion Phases

A hydrochemical facies evolution diagram (HFE‐D) is a multirectangular diagram, which is a useful tool in the interpretation of sea water intrusion processes. This method note describes a simple method for generating an HFE‐D plot using the spreadsheet software package, Microsoft Excel. The code was applied to groundwater from the alluvial coastal plain of Grosseto (Tuscany, Italy), which is characterized by a complex salinization process in which sea water mixes with sulfate or bicarbonate recharge water.     

Hybrid simulation of a multi‐span RC viaduct with plain bars and sliding bearings

This paper deals with the seismic response assessment of an old reinforced concrete viaduct and the effectiveness of friction‐based retrofitting systems. Emphasis was laid on an old bridge, not properly designed to resist seismic action, consisting of 12 portal piers that support a 13‐span bay deck for each independent roadway. On the basis of an OpenSEES finite element frame pier model, calibrated in a previous experimental campaign with cyclic displacement on three 1:4 scale frame piers, a more complex experimental activity using hybrid simulation has been devised. The aim of the simulation was twofold: (i) to increase knowledge of non‐linear behavior of reinforced concrete frame piers with plain steel rebars and detailing dating from the late 1950s; and (ii) to study the effectiveness of sliding bearings for seismic response mitigation. Hence, to explore the performance of the as built bridge layout and also of the viaduct retrofitted with friction‐based devices, at both serviceability and ultimate limit state conditions, hybrid simulation tests were carried out. In particular, two frame piers were experimentally controlled with eight‐actuator channels in the as built case while two frame piers and eight sliding bearings were controlled with 18‐actuator channels in the isolated case. The remaining frame piers were part of numerical substructures and were updated offline to accurately track damage evolution. Copyright © 2015 John Wiley & Sons, Ltd.     

Oxidative stress, genotoxicity and histopathology biomarker responses in mullet (Mugil cephalus) and sea bass (Dicentrarchus labrax) liver from Bizerte Lagoon (Tunisia)

The aim of the study was to evaluate the impact of environmental contaminants on oxidative stress, genotoxic and histopathologic biomarkers in liver of mullet (Mugil cephalus) and sea bass (Dicentrarchus labrax) collected from a polluted coastal lagoon (Bizerte Lagoon) in comparison to a reference site (the Mediterranean Sea). Antioxidant enzyme activities were lower in fish from the polluted site compared with fish from the reference site, suggesting deficiency of the antioxidant system to compensate for oxidative stress. DNA damage was higher in both fish species from the contaminated site indicating genotoxic effects. The liver histopathological analysis revealed alterations in fish from Bizerte Lagoon. Hepatocytes from both fish species featured extensive lipid-type vacuolation and membrane disruption. Results suggest that the selected biomarkers in both fish species are useful for the assessment of pollution impacts in coastal environments influenced by multiple pollution sources.     

Localized algal blooms induced by river inflows in a canyon type reservoir

The local response of the phytoplankton community to river inflow processes was investigated with modeling and field analyses in a long and narrow, stratified reservoir in mid-summer. The river water had high concentrations of phosphorus and nitrogen (ammonium and nitrate) and temperature had large variations at diurnal scales. As a consequence of the large variation in river temperature, the level of neutral buoyancy (the depth where the river water spreads laterally in the reservoir) oscillated between the surface (overflows) during the day, and the depth of the metalimnion (interflows) during the night. The reservoir remained strongly stratified, which favoured the presence of cyanobacteria. It is shown that under these conditions, nutrient-rich river water injected during overflows into the surface layers promoted the occurrence of localized algal blooms in the zones where the overflow mixed with the quiescent water of the reservoir. A series of hydrodynamic simulations of the reservoir were conducted both with synthetic and realistic forcing to assess the importance of river temperatures and wind-driven hydrodynamics for algal blooms. The simulations confirmed that the river inflow was the main forcing mechanism generating the localized bloom.     

Seismic tomography of Central São Miguel, Azores

We determine the three-dimensional distribution of P- and S-wave velocities for Central São Miguel Island (Azores, Portugal) by tomographic inversion of local earthquake arrival times. We use P- and S-phases from 289 earthquakes recorded by a network of 20 seismometers. The model shows good resolution in the shallowest 5–6 km, as illustrated by different resolution tests. There are several velocity anomalies, interpreted as pyroclastic deposits, intrusive bodies, geothermal fields, and the effects of tectonics. A low Vp zone marks Furnas caldera, probably evidencing volcaniclastic sediments with development of intense geothermal activity. Another low Vp zone extends in correspondence of the highly fractured area between Fogo and the north coast. Conversely, strong positive anomalies are found south of Fogo and northwest of Furnas. They are interpreted in terms of high-density deposits and remnants of a plutonic intrusion. These interpretations are supported by the distribution of Vp/Vs, and are consistent with previous geological, geochemical, and geophysical data.