A Linking Test to reduce the number of hydraulic parameters necessary to simulate groundwater recharge in unsaturated soils

In environmental studies, numerical simulation models are valuable tools for testing hypothesis about systems functioning and to perform sensitivity studies under scenarios of land use or climate changes. The simulations depend upon parameters which are not always measurable quantities and must be calibrated against observations, using for instance inverse modelling. Due to the scarcity of these observations, it has been found that parameter sets allowing a good matching between simulated and measured quantities are often non-unique, leading to the problem of equifinality. This can lead to non-physical values, erroneous fluxes and misleading sensitivity analysis. Therefore, a simple but robust inverse method coined the Linking Test is presented to determine if the parameters are linked. Linked parameters are then sub-divided into classes according to their impact on water fluxes. The Linking Test establishes the causes of non-uniqueness of parameter sets and the feasibility of the inverse modelling.     

A measurement at the first acoustic peak of the cosmic microwave background with the 33-GHz interferometer

This paper presents the results from the Jodrell BankInstituto de Astrofisicia de Canarias (IAC) two-element 33-GHz interferometer operated with an element separation of 32.9 wavelengths and hence sensitive to 1°-scale structure on the sky. The level of cosmic microwave background (CMB) fluctuations, assuming a flat CMB spatial power spectrum over the range of multipoles =208±18, was found using a likelihood analysis to be at the 68 per cent confidence level, after the subtraction of the contribution of monitored point sources. Other possible foreground contributions have been assessed and are expected to have negligible impact on this result.     

The role of chilean mountain areas in time of drought and energy crisis: New pressures and challenges for vulnerable ecosystems

In the summer of 2010/2011 Chile suffered the third most severe energy and water supply crisis in only one decade.This may be surprising as the Andes which accompany the country along 4,200 km are a water tower and could provide more electricity and water than needed.On top of that,it has to be mentioned that Chile also counts with sunny and windy climates and with excellent geothermal energy resources and thus has a huge potential as far as renewable energies are concerned.After analyzing the existing natural conditions,the infrastructure and the present challenges of climate change,it has to be asked in which way Chile can make use of this potential in the near future,considering the legal and political situation and the technological opportunities.It seems that the resources are still hidden in the Andes,and only the key is missing to realize the country’s natural potential.This research has been based on the analysis of existing literature,media,quantitative data from government institutions and other antecedents obtained by the authors in field work done in the South of Chile in 2010.The added value of this compilation lies in the comprehensive perspective,linking the knowledge of climatologists,hydrologists,mountain researchers and energy experts in order to support a sustainable energy and water supply for the future in Chile.From this present research,it can be concluded that Chile necessarilyhas to adopt new energy-related strategies,particularly those aimed at diminishing the strong dependence on traditional sources of energy and establishing new techniques and technologies for generating electricity and utilizing the vast potential that the country is ready to offer,such as that provided by the Andes along 4,200 kilometers.     

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.     

Enrichment of rare earth elements as environmental tracers of contamination by acid mine drainage in salt marshes: A new perspective

Rare earth elements (REE) were analyzed in surface sediments from the Guadiana Estuary (SW Iberian Pyrite Belt). NASC (North American Shale Composite) normalized REE patterns show clearly convex curvatures in middle-REE (MREE) with respect to light- and heavy-REE, indicating acid-mixing processes between fluvial waters affected by acid mine drainage (AMD) and seawater. However, REE distributions in the mouth (closer to the coastal area) show slightly LREE-enriched and flat patterns, indicating saline-mixing processes typical of the coastal zone. NASC-normalized ratios (La/Gd and La/Yb) do not discriminate between both mixing processes in the estuary. Instead, a new parameter (E(MREE)) has been applied to measure the curvature in the MREE segment. The values of E(MREE)>0 are indicative of acid signatures and their spatial distribution reveal the existence of two decantation zones from flocculation processes related to drought periods and flood events. Studying REE fractionation through the E(MREE) may serve as a good proxy for AMD-pollution in estuarine environments in relation to the traditional methods.     

Complex dynamics of small-moderate volcanic events: the example of the 2011 rhyolitic Cordón Caulle eruption,Chile

After decades of repose, Puyehue-Cordón Caulle Volcano (Chile) erupted in June 2011 following a month of continuously increasing seismic activity. The eruption dispersed a large volume of rhyolitic tephra over a wide area and was characterized by complex dynamics. During the initial climactic phase of the eruption (24–30 h on 4–5 June), 11–14-km-high plumes dispersed most of the erupted tephra eastward towards Argentina, reaching as far as the Atlantic Ocean. This first eruptive phase was followed by activity of lower intensity, leading to the development of a complex stratigraphic sequence, mainly due to rapid shifts in wind direction and eruptive style. The resulting tephra deposits consist of 13 main layers grouped into four units. Each layer was characterized based on its dispersal direction, sedimentological features, and on the main characteristics of the juvenile fraction (texture, density, petrography, chemistry). The lowest part of the eruptive sequence (Unit I), corresponding to the tephra emitted between 4 and 5 June, is composed of alternating lapilli layers with a total estimated volume of ca. 0.75 km³; these layers record the highest intensity phase, during which a bent-over plume dispersed tephra towards the southeast-east, with negligible up-wind sedimentation. Products emitted during 5–6 June (Unit II) signaled an abrupt shift in wind direction towards the north, leading to the deposition of a coarse ash deposit in the northern sector (ca. 0.21 km³ in volume), followed by a resumption of easterly directed winds. A third phase (Unit III) began on 7 June and resulted in tephra deposits in the eastern sector and ballistic bombs around the vent area. A final phase (Unit IV) started after 15 June and was characterized by the emission of fine-grained white tephra from ash-charged plumes during low-level activity and the extrusion of a viscous lava flow. Timing and duration of the first eruptive phases were constrained based on comparison of the dispersal of the main tephra layers with satellite images, showing that most of the tephra was emitted during the first 72 h of the event. The analyzed juvenile material tightly clusters within the rhyolitic field, with negligible chemical variations through the eruptive sequence. Textural observations reveal that changes in eruption intensity (and consequently in magma ascent velocity within the conduit) and complex interactions between gas-rich and gas-depleted magma portions during ascent resulted in vesicular clasts with variable degrees of shear localization, and possibly in the large heterogeneity of the juvenile material.     

Modelling-based assessment of suspended sediment dynamics in a hypertidal estuarine channel

We investigate the dynamics of suspended sediment transport in a hypertidal estuarine channel which displays a vertically sheared exchange flow. We apply a three-dimensional process-based model coupling hydrodynamics, turbulence and sediment transport to the Dee Estuary, in the north-west region of the UK. The numerical model is used to reproduce observations of suspended sediment and to assess physical processes responsible for the observed suspended sediment concentration patterns. The study period focuses on a calm period during which wave-current interactions can reasonably be neglected. Good agreement between model and observations has been obtained. A series of numerical experiments aim to isolate specific processes and confirm that the suspended sediment dynamics result primarily from advection of a longitudinal gradient in concentration during our study period, combined with resuspension and vertical exchange processes. Horizontal advection of sediment presents a strong semi-diurnal variability, while vertical exchange processes (including time-varying settling as a proxy for flocculation) exhibit a quarter-diurnal variability. Sediment input from the river is found to have very little importance, and spatial gradients in suspended concentration are generated by spatial heterogeneity in bed sediment characteristics and spatial variations in turbulence and bed shear stress.     

Traveltime approximations for q‐P waves in vertical transversely isotropy media*

As exploration targets have become deeper, cable lengths have increased accordingly, making the conventional two term hyperbolic traveltime approximation produce increasingly erroneous traveltimes. To overcome this problem, many traveltime formulas were proposed in the literature that provide approximations of different quality. In this paper, we concentrate on simple traveltime approximations that depend on a single anisotropy parameter. We give an overview of a collection of such traveltime approximations found in the literature and compare their quality. Moreover, we propose some new single‐parameter traveltime approximations based on the approximations found in the literature. The main advantage of our approximations is that some of them are rather simple analytic expressions that make them easy to use, while achieving the same quality as the better of the established formulas.     

Assessing coastal benthic macrofauna community condition using best professional judgement - Developing consensus across North America and Europe

Benthic indices are typically developed independently by habitat, making their incorporation into large geographic scale assessments potentially problematic because of scaling inequities. A potential solution is to establish common scaling using expert best professional judgment (BPJ). To test if experts from different geographies agree on condition assessment, sixteen experts from four regions in USA and Europe were provided species-abundance data for twelve sites per region. They ranked samples from best to worst condition and classified samples into four condition (quality) categories. Site rankings were highly correlated among experts, regardless of whether they were assessing samples from their home region. There was also good agreement on condition category, though agreement was better for samples at extremes of the disturbance gradient. The absence of regional bias suggests that expert judgment is a viable means for establishing a uniform scale to calibrate indices consistently across geographic regions.