Spring recharge and groundwater flow patterns in flysch aquifer in the Po(l)onina Wetli(n)ska Massif in the Carpathian Mountains

Flysch-type aquifers in the Eastern Carpathians usually feed periodic and low-discharge springs.However,in some areas,such as in the upper part of the Po(l)onin...     

Dynamics of co-ignimbrite plumes generated from pyroclastic flows of Mount St. Helens (7 August 1980)

 Four co-ignimbrite plumes were generated along the flow path of the pyroclastic flow of 7 August 1980 at Mount St. Helens. Three of the plumes were generated in discrete pulses which can be linked to changes in slope along the channel. One plume was generated at the mouth of the channel where the flow decelerated markedly as it moved onto the lower slopes of the pumice plain. Plume generation here may be triggered by enhanced mixing due to a hydraulic jump associated with an abrupt slope change. Measurements of plume ascent velocity and width show that the co-ignimbrite plumes increased in velocity with height. The plumes have initial velocities of 1–2 m/s. Two of the plumes reached a velocity maximum (4.6 and 8.8 m/s, respectively, at heights of 270 and 315 m above the flow) and thereafter decelerated. The other plumes reached velocities of 6.2 and 13 m/s. The four plumes become systematically less energetic downstream as measured by their ascent rates, which can be interpreted as a consequence of decreasing interaction of the pyroclastic flow front with the atmosphere. Theoretical models of both co-ignimbrite plumes and discrete co-ignimbrite clouds assume that there is no initial momentum, and both are able to predict the observed acceleration stage. The rising plumes mix with and heat air and sediment out particles causing their buoyancy to increase. Theoretical models agree well with observations and suggest that the initial motion of the ascending material is best described as a discrete thermal cloud which expands as it entrains air, whereas the subsequent motion of the head may become influenced by material supplied from the following plume. The models agree well with observations for an initial temperature of the ash and air mixture in the range of 500–600 K, which is in turn consistent with the measured initial ash temperature of around 920 K. Ash masses of 3.4×10⁵ to 1.8×10⁶ kg are estimated. Received: 11 January 1996 / Accepted: 7 October 1996     

Use of Sonication for Enhanced Sampling of Attached Microbes from Groundwater Systems

The vast majority of microorganisms in aquifers live as biofilms on sediment surfaces, which presents significant challenges for sampling as only the suspended microbes will be sampled through normal pumping. The use of a down-well low frequency sonicator has been suggested as a method of detaching microbes from the biofilm and allowing rapid sampling of this community. We developed a portable, easy to use, low-frequency electric sonicator and evaluated its performance for a range of well depths (tested up to 42 m below ground level) and casing types. Three sonicators were characterized in laboratory experiments using a 1 m long tank filled with pea gravel. These included a commercially available pneumatic sonicator, a rotating flexible shaft sonicator, and the prototype electric sonicator. The electric sonicator detached between 56 and 74% of microbes grown on gravel-containing biobags at distances ranging between 2 and 50 cm from the sonicator. The field testing comprises of a total of 55 sampling events from 48 wells located in 4 regions throughout New Zealand. Pre- and post-sonication samples showed an average 33 times increase in bacterial counts. Microbial sequence data showed that the same classes are present in pre- and post-sonicated samples and only slight differences were seen in the proportions present. The sampling process was rapid and the significant increases in bacterial counts mean that microbial samples can be quickly obtained from wells, which permits more detailed analysis than previously possible.     

An assessment of the climate change impacts on groundwater recharge at a continental scale using a probabilistic approach with an ensemble of GCMs

This study used 16 Global Climate Models and three global warming scenarios to make projections of recharge under a 2050 climate for the entire Australian continent at a 0.05° grid resolution. The results from these 48 future climate variants have been fitted to a probability distribution to enable the results to be summarised and uncertainty quantified. The median results project a reduction in recharge across the west, centre and south of Australia and an increase in recharge across the north and a small area in the east of the continent. The range of results is quite large and for large parts of the continent encompasses both increases and decreases in recharge. This makes it difficult to utilise for water resources management so the results have been analysed with a risk analysis framework; this enables the future projections for groundwater recharge to be communicated to water managers in terms of likelihood and consequence of a reduction in recharge. This highlights an important message for water resource managers that in most areas of Australia they will be making decisions on water allocations under considerable uncertainty as to the direction and magnitude of recharge change under a future climate and that this uncertainty may be irreducible.     

Core Density Profile Survival in Dissipationless Mergers

We use N-body experiments to study the survival of power-law density cusps in mergers of spherical galaxy models. Steep cusps (e.g. ρ∝r ^-2) are preserved during mergers of equal-mass models; this may be viewed as a general consequence of the incomplete violent relaxation observed in such mergers. Progenitor profile has a strong effect on remnant shape; steep cusps produce oblate remnants. If bright ellipticals form by hierarchical mergers of faint ones, the lack of steep cusps in these galaxies is somewhat surprising. This revised version was published online in July 2006 with corrections to the Cover Date.     

Constraining probabilistic chloride mass-balance recharge estimates using baseflow and remotely sensed evapotranspiration: the Cambrian Limestone Aquifer in northern Australia

Hydrogeology Journal - Regional-scale estimates of groundwater recharge are inherently uncertain, but this uncertainty is rarely quantified. Quantifying this uncertainty provides an understanding...     

Northern landscapes in transition: Evidence,approach and ways forward using the Krycklan Catchment Study

Improving our ability to detect changes in terrestrial and aquatic systems is a grand challenge in the environmental sciences. In a world experiencing increasingly rapid rates of climate change and ecosystem transformation, our ability to understand and predict how, when, where, and why changes occur is essential for adapting and mitigating human behaviours. In this context, long-term field research infrastructures have a fundamentally important role to play. For northern boreal landscapes, the Krycklan Catchment Study (KCS) has supported monitoring and research aimed at revealing these changes since it was initiated in 1980. Early studies focused on forest regeneration and microclimatic conditions, nutrient balances and forest hydrology, which included monitoring climate variables, water balance components, and stream water chemistry. The research infrastructure has expanded over the years to encompass a 6790 ha catchment, which currently includes 11 gauged streams, ca. 1000 soil lysimeters, 150 groundwater wells, >500 permanent forest inventory plots, and a 150 m tall tower (a combined ecosystem-atmosphere station of the ICOS, Integrated Carbon Observation System) for measurements of atmospheric gas concentrations and biosphere-atmosphere exchanges of carbon, water, and energy. In addition, the KCS has also been the focus of numerous high resolution multi-spectral LiDAR measurements and large scale experiments. This large collection of equipment and data generation supports a range of disciplinary studies, but more importantly fosters multi-, trans-, and interdisciplinary research opportunities. The KCS attracts a broad collection of scientists, including biogeochemists, ecologists, foresters, geologists, hydrologists, limnologists, soil scientists, and social scientists, all of whom bring their knowledge and experience to the site. The combination of long-term monitoring, shorter-term research projects, and large-scale experiments, including manipulations of climate and various forest management practices, has contributed much to our understanding of boreal landscape functioning, while also supporting the development of models and guidelines for research, policy, and management.     

Review: Current and emerging methods for catchment-scale modelling of recharge and evapotranspiration from shallow groundwater

A review is provided of the current and emerging methods for modelling catchment-scale recharge and evapotranspiration (ET) in shallow groundwater systems. With increasing availability of data, such as remotely sensed reflectance and land-surface temperature data, it is now possible to model groundwater recharge and ET with more physically realistic complexity and greater levels of confidence. The conceptual representation of recharge and ET in groundwater models is critical in areas with shallow groundwater. The depth dependence of recharge and vegetation water-use feedback requires additional calibration to fluxes as well as heads. Explicit definition of gross recharge vs. net recharge, and groundwater ET vs. unsaturated zone ET, in preparing model inputs and reporting model results is necessary to avoid double accounting in the water balance. Methods for modelling recharge and ET include (1) use of simple surface boundary conditions for groundwater flow models, (2) coupling saturated groundwater models with one-dimensional unsaturated-zone models, and (3) more complex fully-coupled surface-unsaturated-saturated conceptualisations. Model emulation provides a means for including complex model behaviours with lower computational effort. A precise ET surface input is essential for accurate model outputs, and the model conceptualisation depends on the spatial and temporal scales under investigation. Using remote sensing information for recharge and ET inputs in model calibration or in model–data fusion is an area for future research development. Improved use of uncertainty analysis to provide probability bounds for groundwater model outputs, understanding model sensitivity and parameter dependence, and guidance for further field-data acquisition are also areas for future research.     

Becoming Reading Group: reflections on assembling a collegiate,caring collective

ABSTRACT

In neoliberalising universities, collegial and collective practices such as reading groups are often positioned by students, staff and managers as less important than meeting individual KPIs (such as producing research publications, seeking research grants, or meeting the increasing demands of producing quality teaching outcomes.) However, reading groups can be vital for cultivating caring collectives and spaces of collegiality. In this paper we use assemblage thinking to explore 25 years of a Geography reading group at the University of Newcastle. The paper addresses two questions: what does reading together do and make possible; and how might we think about the labours of reading together as a way of building caring collectives. The paper draws on reflections from 24 past and present members of reading group to explore how these kinds of academic practices nourish our working lives.     

Metamorphic record of collision and collapse in the Ediacaran‐Cambrian Araçuaí orogen,SE‐Brazil: Insights from P–T pseudosections and monazite dating

The Araçuaí orogen is the Brazilian counterpart of the Araçuaí‐West Congo orogenic system (AWCO), a component of the Ediacaran‐Cambrian orogenic network formed during the amalgamation of West Gondwana. The northwestern portion of the Araçuaí orogen is dominated by a succession of metasedimentary rocks made up of Meso‐ to Neoproterozoic rift, passive margin and syn‐orogenic sequences, locally intruded by post‐collisional granites. These sequences are involved in three distinct tectonic units, which from west to east are: the southern Espinhaço fold‐thrust system (SE‐thrust system), the normal‐sense Chapada Acauã shear zone (CASZ) and the Salinas synclinorium. Three deformation phases were documented in the region. The first two phases (D₁ and D₂) are characterized by contractional structures and represent the collisional development stage of the orogen. The third phase (D₃) is extensional and currently viewed as a manifestation of orogenic collapse of the system. The distribution of the metamorphic mineral assemblages in the region characterizes two metamorphic domains. The M‐Domain I on the west, encompassing the SE‐thrust system and the CASZ, is marked by a syn‐collisional (syn‐D₁) Barrovian‐type metamorphism with P–T conditions increasing eastwards and reaching ~8.5 kbar at ~650°C between 575 and 565 Ma. The M‐Domain II comprises the Salinas synclinorium in the hangingwall of the CASZ, and besides the greenschist facies syn‐collisional metamorphism, records mainly a Buchan‐type metamorphic event, which took place under 3–5.5 kbar and up to 640°C at c. 530 Ma. The northwestern Araçuaí orogen exhibits, thus, a paired metamorphic pattern, in which the Barrovian and Buchan‐type metamorphic domains are juxtaposed by a normal‐sense shear zone. Lithospheric thinning during the extensional collapse of the orogen promoted ascent of the geotherms and melt generation. A large volume of granites was emplaced in the high grade and anatectic core of the orogen during this stage, and heat advected from these intrusions caused the development of Buchan facies series over a relatively large area. Renewed granite plutonism, hydrothermal activities followed by progressive cooling affected the system between 530 and 490 Ma.