analytical expressions for transient specific yield and shallow water table drainage 1 new closed form expressions are introduced to capture the dependence of specific yield on time and depth to water table the expressions allow the user to convert observations of water table fluctuations to volumes of water released from storage in a shallow water table aquifer whereas a linear relationship between water table fluctuations and released volumes holds for a deep water table aquifer this relationship is nonlinear for shallow water table aquifers the dependence of specific yield on time stems from the slow drainage of soil water from pores above the water table the new expressions allow determination of transient specific yield and time to drain the soil water profile for a given water table fluctuation if the time step in a numerical groundwater model is longer than the time for limiting specific yield then a constant time independent specific yield can be justifiably adopted the new expressions are easy to use and require knowledge of soil hydraulic properties which are readily available from soil water retention data and surveys

the origin and evolution of skarn forming fluids from the phu lon deposit northern loei fold belt thailand evidence from fluid inclusion and sulfur isotope studies abstract the phu lon skarn cu au deposit is located in the northern loei fold belt lfb thailand it is hosted by devonian volcano sedimentary sequences intercalated with limestone and marble units intruded by diorite and quartz monzonite porphyries phu lon is a calcic skarn with both endoskarn and exoskarn facies in both skarn facies andradite and diopside comprise the main prograde skarn minerals whereas epidote chlorite tremolite actinolite and calcite are the principal retrograde skarn minerals four types of fluid inclusions in garnet were distinguished 1 liquid rich inclusions 2 daughter mineral bearing inclusions 3 salt saturated inclusions and 4 vapor rich inclusions epidote contains only one type of fluid inclusion liquid rich inclusions fluid inclusions associated with garnet prograde skarn stage display high homogenization temperatures and moderate salinities 421 6 468 5 c 17 4 23 1 wt nacl equiv by contrast fluid inclusions associated with epidote retrograde skarn stage record lower homogenization temperatures and salinities 350 9 399 8 c 0 5 8 wt nacl equiv these data suggest a possible mixing of saline magmatic fluids with external dilute fluid sources e g meteoric fluids as the system cooled some fluid inclusions in garnet contain hematite daughters suggesting an oxidizing magmatic environment sulfur isotope determinations on sulfide minerals from both the prograde and retrograde stages show a uniform and narrow range of 34 s values 2 6 to 1 1 34 s suggesting that the ore forming fluid contained sulfur of orthomagmatic origin overall the phu lon deposit is interpreted as an oxidized cu au skarn based on the mineralogy and fluid inclusion characteristics

a model for flow in the chalk unsaturated zone incorporating progressive weathering summary groundwater from unconfined chalk aquifers constitutes a major water resource in the uk the unsaturated zone in such systems plays a crucial role in the hydrological cycle determining the timing and magnitude of recharge and the transport and fate of nutrients however despite more than three decades of study our physical understanding of this system is incomplete in this research state of the art instrumentation provided high temporal resolution readings of soil moisture status rainfall and actual evaporation from two sites in the pang and lambourn catchments berkshire uk for a continuous two year period 2004 5 a parsimonious physically based model for the flow of water through the chalk unsaturated zone including a novel representation of the soil and weathered chalk layers was developed the parameters were identified by inverse modelling using field measurements of water content and matric potential the model was driven by rainfall and evaporation data and simulated fluxes throughout the profile including the discrete matrix and fracture components down to the water table but not the water table response results showed that the model was able to reproduce closely the observed changes in soil moisture status recharge was predominantly through the matrix and the recharge response was strongly attenuated with depth however the activation of fast recharge pathways through fractures in the chalk unsaturated zone was highly sensitive to rainfall intensity relatively modest increases in rainfall led to dramatically different recharge patterns with potentially important implications for groundwater flooding the development and migration of zero flux planes with time and depth were simulated the simulations also provided strong evidence that for water table depths greater than 5 m recharge fluxes persist throughout the entire year even during drought conditions with important implications for the calculation of specific yield from baseflow estimates and the representation of recharge in groundwater models

evaluation of aquifer thickness by analysing recession hydrographs application to the oman ophiolite hard rock aquifer for more than a century hydrologists and hydrogeologists have been investigating the processes of stream and spring baseflow recession for obtaining data on aquifer characteristics the maillet formula librairie sci a hermann paris 1905 218 an exponential equation widely used for recession curve analysis is an approximate analytical solution for the diffusion equation in porous media whereas the equation proposed by boussinesq c r acad sci 137 1903 5 j math pure appl 10 1904 5 that depicts baseflow recession as a quadratic form is an exact analytical solution other formulas currently used involve mathematical functions with no basis on groundwater theory only the exact analytical solutions can provide quantitative data on aquifer characteristics the efficiency of the two methods was compared on the basis of recession curves obtained with a 2d cross sectional finite differences model that simulates natural aquifers simulations of shallow aquifers with an impermeable floor at the level of the outlet show that their recession curves have a quadratic form thus the approximate maillet solution largely overestimates the duration of the influenced stage and underestimates the dynamic volume of the aquifer moreover only the boussinesq equations enable correct estimates of the aquifer parameters numerical simulations of more realistic aquifers with an impermeable floor much deeper than the outlet proves the robustness of the boussinesq formula even under conditions far from the simplifying assumptions that were used to integrate the diffusion equation the quadratic form of recession is valid regardless of the thickness of the aquifer under the outlet and provides good estimates of the aquifer s hydrodynamic parameters nevertheless the same numerical simulations show that aquifers with a very deep floor provide an exponential recession thus in that configuration the maillet formula also provides a good fit of recession curves even if parameter estimation remains poor in fact the recession curve appears to be closer to exponential when flow has a very important vertical component and closer to quadratic when horizontal flow is dominant as a consequence aquifer permeability anisotropy also changes the recession form the combined use of the two fitting methods allows one to quantify the thickness of the aquifer under the outlet

fluxes through steady chimneys in a mushy layer during binary alloy solidification solute transport within solidifying binary alloys occurs predominantly by convection from narrow liquid chimneys within a porous mushy layer we develop a simple model that elucidates the dominant structure and driving forces of the flow which could be applied to modelling brine fluxes from sea ice where a cheaply implementable approach is essential a horizontal density gradient within the mushy layer in the vicinity of the chimneys leads to baroclinic torque which sustains the convective flow in the bulk of the mushy layer the isotherms are essentially horizontal in this region we impose a vertically linear temperature field and immediately find that the flow field is a simple corner flow we determine the strength of this flow by finding a similarity solution to the governing mushy layer equations in an active region near the chimney we also determine the corresponding shape of the chimney the vertical structure of the solid fraction and the interstitial flow field we apply this model first to a periodic planar array of chimneys and show analytically that the solute flux through the chimneys is proportional to a mush rayleigh number secondly we extend the model to three dimensions and find that an array of chimneys can be characterized by the average drainage area alone therefore we solve the model in an axisymmetric geometry and find new sometimes nonlinear relationships between the solute flux the rayleigh number and the other dimensionless parameters of the system

modeling the winter spring transition of first year ice in the western weddell sea a new halodynamic scheme is coupled with the los alamos sea ice model to simulate western weddell sea ice during the winter spring transition one dimensional temperature and salinity profiles are consistent with the warming and melt stages exhibited in first year ice cores from the 2004 ice station polarstern ispol expedition results are highly sensitive to snowfall simulations which use reanalysis precipitation data do not retain a snow cover beyond mid december and the warming transition occurs too rapidly model performance is greatly improved by prescribing a snowfall rate based on reported snow thicknesses during ice growth prior to ispol simulations indicate a period of thick snow and upper ice salinity enrichment gravity drainage model parameters impact the simulation immediately while effects from the flushing parameter snow porosity at the ice top appear as the freeboard becomes negative simulations using a snow porosity of 0 3 consistent with that of wet snow agree with salinity observations the model does not include lateral sources of sea water flooding but vertical transport processes account for the high upper ice salinities observed in ice cores at the start of the expedition as the ice warms a fresh upper ice layer forms and the high salinity layer migrates downward this pattern is consistent with the early spring development stages of high porosity layers observed in antarctic sea ice that are associated with rich biological production future extensions of the model may be valuable in antarctic ice biogeochemical applications

in situ measurements of the evolution of young sea ice 1 we present data from in situ measurements of the salinity evolution of young sea ice in the arctic the measurements were carried out with very high vertical and temporal resolution over the course of a few days until the ice had reached a thickness of around 20 cm the measured bulk salinity profiles show that during ice growth sea ice salinity is continuous across the ice ocean interface and that there is no instantaneous loss of salt at the advancing front measured salt fluxes emanating from the ice are as high as 90 g m 2 h 1 during the first few hours of new ice formation and are roughly half as large during later stages of the experiments the bulk salinity within the ice decreases continuously with time from the ocean water salinity to a near steady state value of around 4 parts per thousand ppt these results are interpreted with ideas from mushy layer theory using a rayleigh number to analyze gravity drainage as the driving mechanism for the observed salt loss in our experiments gravity drainage occurs for a critical rayleigh number of around 10 in close agreement with earlier theoretical and experimental studies

physiographic and climatic controls on regional groundwater dynamics the main goal of this study is to explore whether the ideas established by surface water hydrologists in the context of pub predictions in ungauged basins can be useful in hydrogeology the concrete question is whether it is possible to create predictive models for groundwater systems with no or few observations based on knowledge derived from similar groundwater systems which are well observed to do so this study analyses the relationship between temporal dynamics of groundwater levels and climatic and physiographic characteristics the analysis is based on data from 341 wells in southern germany with ten year daily groundwater hydrographs observation wells are used in confined and unconfined sand and gravel aquifers from narrow mountainous valleys as well as more extensive lowland alluvial aquifers groundwater dynamics at each location are summarized with 46 indices describing features of groundwater hydrographs besides borehole log derived geologic information local and regional morphologic characteristics as well as topography derived boundary and climatic descriptors were derived for each well regression relationships were established by mining the data for associations between dynamics and descriptors with forward stepwise regression at a confidence level 95 the most important predictors are geology and boundary conditions and secondarily climate as well as some topographic features such as regional convergence the multiple regression models are in general agreement with process understanding linked to groundwater dynamics in unconfined aquifers this systematic investigation suggests that statistical regionalization of groundwater dynamics in ungauged aquifers based on map derived physiographic and climatic controls may be feasible

impacts of a mushy layer thermodynamic approach in global sea ice simulations using the cice sea ice model we perform global simulations of the los alamos sea ice model cice with a new thermodynamics component that has a fully prognostic variable bulk salinity vertical profile based on mushy layer physics the processes of gravity drainage melt water flushing and snow ice formation are parameterized to allow the bulk salinity to evolve with time we analyze the seasonal and spatial variation of sea ice bulk salinity area volume and thickness and compare these quantities to simulations using the previous thermodynamic component adjusting one of the gravity drainage parameters we find good agreement between simulation results and fieldwork ice core observations of sea ice bulk salinity as expected bulk salinity is highest during periods of ice growth and lowest after periods of ice melt in the northern hemisphere the new thermodynamics component produces thicker ice than the previous thermodynamics component of the nine major differences between the two models differences in how salinities are calculated and how melt pond flushing is parameterized are the principal causes of this thickness difference thickness differences are smaller in the southern hemisphere than in the northern hemisphere since a greater fraction of ice melts and differences cannot accumulate year on year model differences in how ice thickness changes and snow ice formation are calculated are the most important causes of the different thickness between the two thermodynamic components in the southern hemisphere the melt pond area and volume are found to be highly sensitive to a parameter choice controlling drainage through macroscopic holes in the ice in both hemispheres

influence of the sea ice thickness distribution on polar climate in ccsm3 abstract the sea ice simulation of the community climate system model version 3 ccsm3 t42 gx1 and t85 gx1 control simulations is presented and the influence of the parameterized sea ice thickness distribution itd on polar climate conditions is examined this includes an analysis of the change in mean climate conditions and simulated sea ice feedbacks when an itd is included it is found that including a representation of the subgrid scale itd results in larger ice growth rates and thicker sea ice these larger growth rates represent a higher heat loss from the ocean ice column to the atmosphere resulting in warmer surface conditions ocean circulation most notably in the southern hemisphere is also modified by the itd because of the influence of enhanced high latitude ice formation on the ocean buoyancy flux and resulting deep water formation changes in atmospheric circulation also result again most notably in the southern hemisphere there are indications that the itd also modifies simulated sea

review and comparison of models for describing non equilibrium and preferential flow and transport in the vadose zone abstract in this paper we review various approaches for modeling preferential and non equilibrium flow and transport in the vadose zone existing approaches differ in terms of their underlying assumptions and complexity they range from relatively simplistic models to more complex physically based dual porosity dual permeability and multi region type models a relatively simple dual porosity flow model results when the richards equation is combined with composite double hump type equations for the hydraulic properties to account for both soil textural matrix and soil structural fractures macropores peds effects on flow the simplest non equilibrium flow model a single porosity model which distinguishes between actual and equilibrium water contents is based on a formulation by ross and smettem soil sci soc am j 64 2000 1926 that requires only one additional parameter to account for non equilibrium a more complex dual porosity mobile immobile water flow model results when the richards or kinematic wave equations are used for flow in the fractures and immobile water is assumed to exist in the matrix we also discuss various dual permeability models including the formulation of gerke and van genuchten water resour res 29 1993a 305 and the kinematic wave approach as used in the macro model of jarvis technical description and sample simulations department of soil science swedish university of agricultural science uppsala sweden 1994 51 both of these models invoke terms accounting for the exchange of water and solutes between the matrix and the fractures advantages and disadvantages of the different models are discussed and the need for inter code comparison is stressed especially against field data that are sufficiently comprehensive to allow calibration validation of the more complex models and to distinguish between alternative modeling concepts several examples and comparisons of equilibrium and various non equilibrium flow and transport models are also provided

a simple dynamical model for gravity drainage of brine from growing sea ice 1 gravity drainage of brine through liquid brine channels is the dominant mechanism for the desalination of growing sea ice we describe and determine mathematically the essential physics of this process elucidating the connection between downward flow in brine channels and a convective upward flow in the rest of the porous ice which we show has a vertically linear structure and strength proportional to a rayleigh number our simple dynamical model of this process is used to interpret the exponential propagation of dye fronts in laboratory experiments we propose that using our new derived parameterization for gravity drainage in sea ice in terms of two unknown parameters could lead to computationally feasible improvements to thermodynamic sea ice models

a physically based parameterization of gravity drainage for sea ice modeling we incorporate a physically derived parameterization of gravity drainage in terms of a convective upwelling velocity into a one dimensional thermodynamic sea ice model of the kind currently used in coupled climate models our parameterization uses a local rayleigh number to represent the important feedback between ice salinity porosity permeability and desalination rate it allows us to determine salt fluxes from sea ice and the corresponding evolution of the bulk salinity of the ice in contrast to older established models that prescribe the ice salinity this improves the predictive power of climate models in terms of buoyancy fluxes to the polar oceans and also the thermal properties of sea ice which depend on its salinity we analyze the behavior of existing fixed salinity models elucidate the physics by which changing salinity affects ice growth and compare against our dynamic salinity model both in terms of laboratory experiments and also deep ocean calculations these comparisons explain why the direct effect of ice salinity on growth is relatively small though not always negligible and sometimes different from previous studies and also highlight substantial differences in the qualitative pattern and quantitative magnitude of salt fluxes into the polar oceans our study is particularly relevant to growing first year ice when gravity drainage is the dominant mechanism by which ice desalinates we expect that our dynamic model which respects the underlying physics of brine drainage should be more robust to changes in polar climate and more responsive to rapid changes in oceanic and atmospheric forcing

on the use of the boussinesq equation for interpreting recession hydrographs from sloping aquifers 1 the method of recession analysis proposed by brutsaert and nieber 1977 remains one of the few analytical tools for estimating aquifer hydraulic parameters at the field scale and beyond in the method the recession hydrograph is examined as dq dt f q where q is aquifer discharge and f is an arbitrary function the observed function f is parameterized through analytical solutions to the one dimensional boussinesq equation for unconfined flow in a homogeneous and horizontal aquifer while attractive in its simplicity as originally presented it is not applicable to settings where slope is an important driver of flow or where hydraulic parameters vary greatly with depth we compare analytical solutions to the linearized one dimensional boussinesq equation for a sloping aquifer to numerical solutions of the full nonlinear equation the behavior of the nonlinear boussinesq equation is also assessed when the aquifer is heterogeneous wherein the lateral saturated hydraulic conductivity k varies as a power law with height z above the impermeable layer k zn n constant 0 all of the analytical solutions differ in key aspects from the nonlinear solution when plotted as dq dt f q and thus are inappropriate for a brutsaert and nieber type analysis however new analytical solutions for a sloping aquifer are derived empirically from the numerical simulations that are applicable during the late period of recession when the recession curve converges to dq dt aqb where b 2n 1 n 1 and a is a function of the dimensions and hydraulic properties of the aquifer

sea ice is a mushy layer sea ice is a two phase two component reactive porous medium an example of what is known in other contexts as a mushy layer the fundamental conservation laws underlying the mathematical description of mushy layers provide a robust foundation for the prediction of sea ice evolution here we show that the general equations describing mushy layers reduce to the model of maykut and untersteiner 1971 under the same approximations employed therein

time to reach near steady state in large aquifers 1 a new analytical solution of the flow equation has been developed to estimate the time to reach a near equilibrium state in mixed aquifers i e having unconfined and confined portions following a large hydraulic perturbation near equilibrium is defined as the time for an initial aquifer perturbation to dissipate by an average 95 across the aquifer the new solution has been obtained by solving the flow system of a simplified conceptual model of a mixed aquifer using laplace transforms the conceptual model is based on two assumptions 1 the groundwater flow can be reduced to a horizontal 1 d problem and 2 the transmissivity a function of the saturated thickness is assumed constant on the unconfined portion this new solution depends on the storativity of the unconfined portion the lengths of the unconfined and confined portions and the transmissivity assumed to be constant and equal in both portions of the mixed aquifer this solution was then tested and validated against a numerical flow model where the variations of the saturated thickness and therefore variations of the transmissivity were either ignored or properly modeled the agreement between the results from the new solution and those from the numerical model is good validating the use of this new solution to estimate the time to reach near equilibrium in mixed aquifers this solution for mixed aquifers as well as the solutions for a fully confined or fully unconfined aquifer has been used to estimate the time to reach near equilibrium in 13 large aquifers in the world for those different aquifers the time to reach near equilibrium ranges between 0 7 kyr to 2 4 107 kyr these results suggest that the present hydraulic heads in these aquifers are typically a mixture of responses induced from current and past hydrologic conditions and thus climate conditions for some aquifers the modern hydraulic heads may in fact depend upon hydrologic conditions resulting from several past climate cycles

combining unsaturated and saturated hydraulic observations to understand and estimate groundwater recharge through glacial till summary although there has been much previous research into various aspects of the flow mechanisms through glacial till an integrated analysis of the flow system from the ground surface to the aquifer is lacking this paper describes such an approach with reference to a detailed field study of the hydraulic processes controlling groundwater recharge through lodgement till in shropshire uk a fieldsite was instrumented with tensiometers and piezometers at a range of depths through the profile and the geology investigated in detail through field and laboratory testing the median matrix hydraulic conductivity of the 6 m thick till is found to be around 2 10 10 m s on the basis of laboratory measurements using the barometric efficiency of the till derived from on site pressure responses the specific storage for the till is found to be in the range 2 10 6 6 10 6 m 1 and approximately 3 10 6 m 1 for the underlying permo triassic sandstone the regional aquifer the hydraulic data indicate that till water table responses to rainfall occur during the summer period even when large tensions are present higher in the profile this is thought to be due to preferential flow through hydraulically active fractures in the till which were observed in a test pit dug on site the field evidence indicates that the fractures are usually infilled with a variety of materials derived and transported from clasts within the till the bulk hydraulic conductivity of the till seems to be greatly enhanced by these features and it is shown on the basis of hydraulic testing and numerical modelling that the bulk hydraulic conductivity of the till is orders of magnitude greater than that of the till matrix and reduces with depth below ground surface the paper furthers understanding of the hydraulic processes contributing to recharge through till and makes the link between the detail of these processes and simplified models of recharge estimation which may be needed for larger scale water resource studies the results are relevant also to contaminant migration studies and aquifer vulnerability assessments

recharge from an ephemeral stream following wetting front arrival to water table after the infiltration wetting front from a river bed of an ephemeral stream in flood reaches the shallow water table the rate of recharge which is also that of infiltration is affected by the development of a groundwater mound the effect is practically immediate if the water content behind the wetting front is close to saturation an approximate analytical solution is developed in that case which predicts the time dependence of the recharge rate comparison with experimental results in the laboratory shows that the solution is excellent in spite of the assumptions necessary in the derivations as long as the ratio of river width over depth to water table exceeds 2 and as long as the ratio of initial saturated thickness over depth to the water table exceeds 2 5 the analytical solution is essentially exact under most field conditions these ratios are largely exceeded consequently the predictive equation for the time dependence of the recharge is both quite simple to use and adequately accurate for field applications

modeling the transport of passive tracers in sea ice 1 a model for the vertical transport of passive tracers in sea ice is presented two reynolds flux closure approximations are proposed for the tracer velocity dispersion term in the new ice tracer model icet the schemes enhanced molecular diffusion emd and mixing length diffusion mld are suggested parameterizations of gravity drainage the dominant mechanism of desalination in growing sea ice the performance of icet using each parameterization is tested against two experimental studies simulations i compare profiles of brine salinity with passive tracer concentrations during sea ice growth and melt and simulations ii compare bottom boundary salt and brine volume fluxes with passive tracer fluxes and bottom diffusivities icet behavior is evaluated under three salinity forcing prescriptions both schemes successfully reproduce expected tracer concentrations in simulations i when the salinity forcing evolves logarithmically however in simulations ii the mld scheme outperforms emd in two significant ways 1 growth rate trends in the mld diffusivity parallel measurements of brine volume flux while emd bottom diffusivities remain almost constant and 2 mld bottom tracer concentrations decrease with ice growth rate similar to excluded brine salinity while emd trends are contrary hence enhanced molecular diffusion is highly questionable for implementation in models of reactive passive tracers the icet mixing length diffusivity is a viable choice in sea ice biogeochemical modeling it remains a challenge to assess whether mld can provide quantitative estimates of desalination at each time step for use in forcing icet or for implementation in a model of sea ice salinity

thermal evolution of permeability and microstructure in sea ice 1 the fluid permeability k of sea ice constrains a broad range of processes such as the growth and decay of seasonal ice the evolution of summer ice albedo and biomass build up such processes are critical to how sea ice and associated ecosystems respond to climate change however studies of k and its dependence on brine porosity and microstructure are sparse here we present a multifaceted theory for k which closely captures laboratory and field data x ray computed tomography provides an unprecedented look at the brine phase and its connectivity we find that sea ice displays universal transport properties remarkably similar to crustal rocks yet over a much narrower temperature range our results yield simple parameterizations for fluid transport in terms of temperature and salinity and permit more realistic representations of sea ice in global climate and biological models

the importance of hydraulic groundwater theory in catchment hydrology the legacy of wilfried brutsaert and jean yves parlange based on a literature overview this paper summarizes the impact and legacy of the contributions of wilfried brutsaert and jean yves parlange cornell university with respect to the current state of the art understanding in hydraulic groundwater theory forming the basis of many applications in catchment hydrology ranging from drought flow analysis to surface water groundwater interactions hydraulic groundwater theory simplifies the description of water flow in unconfined riparian and perched aquifers through assumptions attributed to dupuit and forchheimer boussinesq 1877 derived a general equation to study flow dynamics of unconfined aquifers in uniformly sloping hillslopes resulting in a remarkably accurate and applicable family of results though often challenging to solve due to its nonlinear form under certain conditions the boussinesq equation can be solved analytically allowing compact representation of soil and geomorphological controls on unconfined aquifer storage and release dynamics the boussinesq equation has been extended to account for flow divergence convergence as well as for nonuniform bedrock slope concave convex the extended boussinesq equation has been favorably compared to numerical solutions of the three dimensional richards equation confirming its validity under certain geometric conditions analytical solutions of the linearized original and extended boussinesq equations led to the formulation of similarity indices for baseflow recession analysis including scaling rules to predict the moments of baseflow response validation of theoretical recession parameters on real world streamflow data is complicated due to limited measurement accuracy changing boundary conditions and the strong coupling between the saturated aquifer with the overlying unsaturated zone however recent advances are shown to have mitigated several of these issues the extended boussinesq equation has been successfully applied to represent baseflow dynamics in catchment scale hydrological models and it is currently considered to represent lateral redistribution of groundwater in land surface schemes applied in global circulation models from the review it is clear that wilfried brutsaert and jean yves parlange stimulated a body of research that has led to several fundamental discoveries and practical applications with important contributions in hydrological modeling

a petrological and fluid inclusion study of magnetite scheelite skarn mineralization at kara northwestern tasmania implications for ore genesis abstract the kara magnetite scheelite deposit is located about 40 km south of burnie in northwestern tasmania the deposit consists of a number of orebodies and the total mineable reserves are 1 7 mt of magnetite at 30 fe and 0 3 mt of scheelite at 0 52 wo3 the major orebodies at kara are hosted by the ordovician gordon limestone at the southern end of the devonian housetop granite adjacent to the granite or separated from it by the ordovician moina sandstone at least four paragenetic stages of skarn formation and ore deposition have been recognized stage i clinopyroxene garnet vesuvianite wollastonite quartz scheelite stage ii garnet vesuvianite magnetite scheelite apatite quartz stage iii magnetite amphibole epidote fluorite quartz chlorite garnet vesuvianite scheelite carbonate pyrite clinopyroxene and stage iv hematite fluorite calcite quartz fluid inclusions in clinopyroxene from stage i homogenize at 460 620 c mode 520 c stage ii gave homogenization temperatures of 349 578 c mode 500 c from scheelite and 360 570 c mode 500 c from vesuvianite the stage i clinopyroxene gave a salinity range of 10 0 12 0 equiv wt nacl with only one low value of 2 0 equiv wt nacl the stage ii mineral assemblages also showed moderate salinities of 12 0 and 17 8 equiv wt nacl from scheelite and vesuvianite fluid inclusions in quartz scheelite calcite and fluorite from the main scheelite mineralization phase stage iii homogenize at 230 360 c with a mode at 300 c and salinity varies from 0 2 to 19 8 equiv wt nacl the mineral paragenetic and fluid inclusion studies indicate that magnetite scheelite mineralization at kara was formed as a proximal skarn assemblage in carbonate host the skarn formation and ore deposition occurred in stages starting with prograde anhydrous clinopyroxene garnet metasomatism at relatively high temperatures 500 c this early assemblage was replaced by the subsequent retrograde deposition of hydrous mineral phases e g amphibole epidote and chlorite as temperatures decreased to 300 c or less deposition of scheelite predominantly occurred in association with hydrous minerals e g amphibole in stage iii the high temperature and moderate to high salinity ore fluids in early anhydrous skarn formation stages i and ii are consistent with fluids of magmatic origin in comparison the lower temperature and variable salinity from high 19 8 equiv wt nacl to as low as 0 2 equiv wt nacl in stage iii suggests a possible involvement of low salinity meteoric waters mixing with high salinity fluids originating from the nearby granite in the later hydrous skarn and ore formation

modeling brine and nutrient dynamics in antarctic sea ice the case of dissolved silica sea ice ecosystems are characterized by microalgae living in brine inclusions the growth rate of ice algae depends on light and nutrient supply here the interactions between nutrients and brine dynamics under the influence of algae are investigated using a one dimensional model the model includes snow and ice thermodynamics with brine physics and an idealized sea ice biological component characterized by one nutrient namely dissolved silica dsi in the model dsi follows brine motion and is consumed by ice algae depending on physical ice characteristics the brine flow is either advective diffusive or turbulent the vertical profiles of ice salinity and dsi concentration are solutions of advection diffusion equations the model is configured to simulate the typical thermodynamic regimes of first year antarctic pack ice the simulated vertical profiles of salinity and dsi qualitatively reproduce observations analysis of results highlights the role of convection in the lowermost 5 10 cm of ice convection mixes saline nutrient poor brine with comparatively fresh nutrient rich seawater this implies a rejection of salt to the ocean and a flux of dsi to the ice in the presence of growing algae the simulated ocean to ice dsi flux increases by 0 115 compared to an abiotic situation in turn primary production and brine convection act in synergy to form a nutrient pump the other important processes are the flooding of the surface by seawater and the percolation of meltwater the former refills nutrients near the ice surface in spring the latter if present tends to expell nutrients from the ice in summer

the phase evolution of young sea ice sea ice forms as a porous matrix consisting of pure ice crystals in equilibrium with brine we present an experimental and theoretical study that reveals that the brine expelled by growing sea ice initially remains trapped within the crystalline interstices but that drainage into the underlying water is ultimately triggered abruptly due to the onset of buoyancy driven convection the onset is quantified by a critical porous medium rayleigh number and we present an empirical marginal stability diagram that defines the transition

desalination processes of sea ice revisited 1 we reexamine five processes that have been suggested to be important for the loss of salt from sea ice these processes are the initial fractionation of salt at the ice ocean interface brine diffusion brine expulsion gravity drainage and flushing with surface meltwater we present results from analytical and numerical studies as well as from laboratory and field experiments that show that among these processes only gravity drainage and flushing contribute to any measurable net loss of salt we show that during ice growth the salinity field is continuous across the ice ocean interface hence there is no immediate segregation of salt at the advancing front

a new analytical method for groundwater recharge and discharge estimation summary a new analytical method was proposed for groundwater recharge and discharge estimation in an unconfined aquifer the method is based on an analytical solution to the boussinesq equation linearized in terms of h2 where h is the water table elevation with a time dependent source term the solution derived was validated with numerical simulation and was shown to be a better approximation than an existing solution to the boussinesq equation linearized in terms of h by calibrating against the observed water levels in a monitoring well during a period of 100 days we shown that the method proposed in this study can be used to estimate daily recharge r and evapotranspiration et as well as the lateral drainage it was shown that the total r was reasonably estimated with a water table fluctuation wtf method if the water table measurements away from a fixed head boundary were used but the total et was overestimated and the total net recharge was underestimated because of the lack of consideration of lateral drainage and aquifer storage in the wtf method

estimating recharge based on long term groundwater table fluctuation monitoring in a shallow aquifer of malaysian tropical rainforest catchment a practical and reliable approach was applied to investigate the groundwater dynamics and obtain natural direct recharge based on the time series of water table fluctuation in moderately flat coastal area with a shallow water table and tropical rainforest weather drainage rate was about 0 034 m day in the study area as estimated by falling groundwater table in period of no rainfall and specific yield values ranged between 0 11 and 0 23 by calculating depth dependent specific yield based on soil water storage for layering soils the method was applied to the monthly data of shallow aquifer at eight field sites in north kelantan river catchment in the period of 1991 2011 the cross correlation and partial cross correlation reveal the acceptable correlation between the water table fluctuation and the rainfall data assuming the time lag from precipitation to water table response is negligible due to shallow water table recharge rates vary with the field sites and mainly depend on soil type and rainfall rather than surface geology although computer simulation with mrcr code was implemented with limited data two series still results are just slightly greater than the field data which indicated the method successfully employed and can be applied in areas with similar conditions in future

analytical expressions for drainable and fillable porosity of phreatic aquifers under vertical fluxes from evapotranspiration and recharge 1 in shallow unconfined aquifers the response of the water table wt to input and output water fluxes is controlled by two distinct storage parameters drainable and fillable porosity which are applicable for wt drawdown and rise respectively however only the drainable porosity estimated from the hydrostatic soil moisture profile is in common use in this study we show that under conditions of evapotranspiration and or recharge from or to a shallow water table drainable and fillable porosity have different values separate analytical expressions are developed for drainable and fillable porosity accounting for dynamic soil moisture conditions through the assumption of successive steady state fluxes in the unsaturated zone the equations are expressed in terms of soil hydraulic parameters and matric suction at the soil surface parametric evapotranspiration and recharge functions are used to estimate the suction at the soil surface the final expressions are independent of evapotranspiration or recharge function thus allowing the use of any appropriate function to estimate the storage parameters it is shown that the occurrence of unsaturated zone fluxes can result in significantly different values of drainable and fillable porosity even when hysteresis is neglected application of the two parameters in a boussinesq type groundwater model resulted in significantly improved estimates of field measured water table dynamics compared to the hydrostatic single parameter model

irrigation return flows in a mediterranean aquifer inferred from combined chloride and stable isotopes mass balances the supply of irrigation water often overcomes crop evapotranspiration and the resulting return flow may infiltrate and significantly contribute to an aquifer water budget despite its crucial importance for water resource management the proportion of irrigation water that contributes to groundwater recharge namely the return flow coefficient often remains difficult to assess here a chloride mass balance is combined with an isotopic mixing model d18o and dd to quantify return flow coefficients in the crau alluvial type aquifer southern france characterized by a long term traditional practice of flood irrigation local groundwater compositions are interpreted in terms of average recharge along different flow paths the high isotopic contrast between irrigation water and regional precipitation al lows the partitioning of recharge between rainfall infiltration and irrigation return flows isotopic mixing proportions are then used to decipher the chloride concentration of groundwater purely recharged by return flow this allows an original application of the chloride mass balance approach to estimate return flow coefficients which doesn t rely on any atmospheric chloride survey values around 0 53 0 16 were found for well defined stream lines averaging the functioning of the upstream aquifer which leads to a return flow rate of 1190 140 mm yr 1 these results are consistent with a local daily time series of recharge fluxes derived from the water table fluctuation method over the 2003 2009 period and in line with the spatial average previously quantified over the whole aquifer this study confirms the ability of geochemical tracers to provide recharge rates fully independent from flux measurements they can be further used to assess the irrigation efficiency in other similar systems or to monitor the variations of irrigation return flow which will result from the future modifications of land use irrigation practices and climate

brine fluxes from growing sea ice it is well known that brine drainage from growing sea ice has a controlling influence on its mechanical electromagnetic biological and transport properties and hence upon the buoyancy forcing and ecology in the polar oceans when the ice has exceeded a critical thickness the drainage process is dominated by brine channels liquid conduits extending through the ice we describe a theoretical model for the drainage process using mushy layer theory which demonstrates that the brine channel spacing is governed by a selection mechanism that maximizes the rate of removal of stored potential energy and hence the brine flux from the system the fluid transport through the sea ice and hence the scaling laws for brine fluxes and brine channel spacings are predicted importantly the resulting brine flux scaling is consistent with experimental data for growth from a fixed temperature surface allowing all parameters in the scaling law to be determined this provides an experimentally tested first principles derivation of a parameterization for brine fluxes from growing sea ice

insights into brine dynamics and sea ice desalination from a 1 d model study of gravity drainage 1 we study gravity drainage using a new 1 d multiphase sea ice model a parametrization of gravity drainage based on the convective nature of gravity drainage is introduced whose free parameters are determined by optimizing model output against laboratory measurements of sea ice salinity evolution optimal estimates of the free parameters as well as the parametrization performance remain stable for vertical grid resolutions from 1 to 30 mm we find a strong link between sea ice growth rate and bulk salinity for constant boundary conditions but only a weak link for more realistic boundary conditions we also demonstrate that surface warming can trigger brine convection over the whole ice layer over a growth season replacing the convective parametrization with constant initial salinities leads to an overall 3 discrepancy of stored energy thermal resistance and salt release we also derive from our convective parametrization a simplified numerically cheap and stable gravity drainage parametrization this parametrization results in an approximately 1 discrepancy of stored energy thermal resistance and salt release compared to the convective parametrization a similarly low discrepancy to our complex parametrization can be reached by simply prescribing a depth dependent salinity profile

straight thinking about groundwater recession while in catchment and hillslope hydrology a more nuanced approach is now taken to streamflow recession analysis in the context of major aquifers it is commonly still assumed that the groundwater head recession rate will take exponential form an idea originally proposed in the 19th century however it is shown here that in early times the groundwater head recession in a major aquifer should take an almost straight line form with a rate approximately equal to the long term recharge rate divided by the aquifer storage coefficient the length of this phase can be estimated from an analytical expression derived in the paper which depends on the aquifer diffusivity length scale and the position of the monitoring point a transitional phase then leads to an exponential phase after some critical time which is independent of the position of the monitoring point major aquifers in a state of periodic quasi steady state are expected to have rates of groundwater flux recession which deviate little from the average rate of groundwater recharge where quasi exponential groundwater declines are observed in nature their form may be diagnostic of particular types of aquifer properties and or boundary effects such as proximity to drainage boundaries variations in transmissivity with hydraulic head storage changes due to pumping nonequilibrium flow at a range of spatial and temporal scales and variations in specific yield with depth recession analysis has applicability to a range of groundwater problems and is powerful way of gaining insight into the hydrologic functioning of an aquifer

growth of and brine drainage from nacl h2o freezing a simulation of young sea ice 1 a numerical simulation is used to predict the early time evolution of the solidification and brine drainage of a binary nacl h2o mixture the mathematical formulation is based on continuum mixture theory as outlined by bennon and incropera 1987 and medjani 1993 results yield a simple relationship between surface temperature and cumulative salt mass draining from the ice additionally a scaling analysis of the energy equation leads to a simple parameterization for ice thickness results compare well with existing laboratory measurements however the delay in onset of brine drainage reported in the literature is not supported by these results images generated using continuum salinity and liquid fraction data overlaid with streamlines generated from velocity data provide a reasonable qualitative resemblance to laboratory observations of nacl h2o ice growth