three dimensional effects causing artifacts in two dimensional cross borehole electrical imaging summary cross borehole electrical resistance tomography ert experiments utilize downhole electrodes typically placed in a borehole filled with material of contrasting resistivity to the host rock the circular geometry of the boreholes is three dimensional and inversion routines are typically two dimensional because of the resistivity contrast artifacts in the form of borehole inversion effects develop in the resistivity images other 3d effects resulting in inversion artifacts are shadow effects caused by use of a 2d code to invert data from a 3d body located outside the image plane in both cases the inversion model misrepresents the spatial change in voltages as a corresponding spatial change in resistivity borehole inversion effects and shadow effects result as the forward solver attempts to resolve the discrepancy in the voltages for numerous electrode pairs into a meaningful resistivity distribution borehole inversion effects are shown to be related to the resistivity contrast between the borehole fill and the host medium and to borehole diameter borehole inversion effects do not materialize with small diameter boreholes e g 0 1 m when the fill resistivity contrast is one order of magnitude or less however a borehole fill resistivity contrast of two orders of magnitude causes artifacts in the form of sheaths near the boreholes and a conductive artifact between the boreholes larger diameter borehole e g 0 2 m induce significant borehole inversion effects with as little as one order of magnitude fill resistivity contrast the general resistivity patterns are similar for the borehole inversion effects however the artifacts are amplified as resistivity contrast and or borehole diameter increase these results are significant because borehole inversion effects may mask a target heterogeneity or an artifact may be confused for an anomaly resulting in improper actions for site characterizations or remediation strategies suggestions of best practices for experimental design to prevent or minimize borehole inversion effects include minimizing borehole diameter minimizing borehole fill resistivity contrast measuring and inputting the resistivity of the borehole fill water into the model and inverting changes in resistivity for time lapse ert data shadow effects are shown to be related directly to the distance of the target heterogeneity out of the image plane our results show that shadow effects become insignificant when the target is between 3 and 5 m outside the 10 m wide image plane because the size of the target and resistivity contrast of the target to the host rock are site specific variables the actual distance at which shadow effects become insignificant will vary from site to site to reduce misinterpretations by shadow effects reduce the dipole length of the four electrode measurements and supplement data from other well pairs and or other methods

electrical resistivity imaging of the architecture of substream sediments 1 the modeling of fluvial systems is constrained by a lack of spatial information about the continuity and structure of streambed sediments there are few methods for noninvasive characterization of streambeds invasive methods using wells and cores fail to provide detailed spatial information on the prevailing architecture and its continuity geophysical techniques play a pivotal role in providing spatial information on subsurface properties and processes across many other environments and we have applied the use of one of those techniques to streambeds we demonstrate through two examples how electrical resistivity imaging can be utilized for characterization of subchannel architecture in the first example electrodes installed in riparian boreholes and on the streambed are used for imaging under the river bed the thickness and continuity of a highly permeable alluvial gravel layer overlying chalk in the second example electrical resistivity images determined from data collected using electrodes installed on the river bed provide a constrained estimate of the sediment volume behind a log jam vital to modeling biogeochemical exchange which had eluded measurement using conventional drilling methods owing to the boulder content of the stream the two examples show that noninvasive electrical resistivity imaging is possible in complex stream environments and provides valuable information about the subsurface architecture beneath the stream channels

field scale time domain spectral induced polarization monitoring of geochemical changes induced by injected co2 in a shallow aquifer contamination of potable groundwater by leaking co2 is a potential risk of carbon sequestration with the help of a field experiment we investigated whether surface monitoring of direct current dc electric resistivity and induced polarization ip could detect geochemical changes induced by co2 in a shallow aquifer forthispurpose weinjectedco2 at depths of 5 and 10 m and monitored its migration using 320 electrodes on a 126 25 m surface grid measured resistances and ip decay curves found a clear signal associated with the injected co2 and rebounded to preinjection values after the end of the injection full decay 2d dc ip inversion was used to invert for the subsurface distribution in cole cole parameters and changes to these parameter fields over time the time lapse inversions found plumes of decreased resistivity and increased normalized chargeability the two plumes were of different shapes with the resistivity anomaly being larger comparison with measurements of electric conductivity and aluminum al concentrations indicated that two geochemical processes were imaged we interpreted the change in resistivity to be associated with the increase in free ions directly caused by the dissolution of co2 whereas the change in normalized chargeability was most likely linked to persistent acidification and best indicated by al concentrations the results highlight the potential for monitoring of field scale geochemical changes by means of surface dc ip measurements especially the different developments of the dc resistivity and normalized chargeability anomalies and the different associated geochemical processes highlight the added value of ip to resistivity monitoring

factors controlling riffle scale hyporheic exchange flows and their seasonal changes in a gaining stream a three dimensional groundwater flow model 1 subsurface flow within a single riffle of a low gradient gravel bed stream was modeled in three dimensions using modflow a finite difference groundwater flow model model simulations showed that exchange flows can only occur in this low gradient gaining stream because of a zone of alluvial sediment around the stream that has much higher permeability than the surrounding catchment k 10 4 m s 1 compared with k 10 6 to 10 8 m s 1 the key factors controlling exchange flow within the alluvial zone were identified as the hydraulic conductivity of the alluvium the hydraulic gradient between upstream and downstream ends of the riffle and the flux of groundwater entering the alluvium from the sides and beneath in the study riffle each of these factors changes with season causing a reversal of flow paths in the alluvium and a reduction in exchange flows from about 0 2 0 5 m 3 d per meter stream length in summer to about 0 008 0 04 m 3 d 1 per meter stream length during fall to spring the model also revealed that exchange flows are up to twice as strong but more variable at the sides of the stream than near the center and that vertical flow paths beneath the channel are more persistent under the range of conditions modeled than lateral flow paths into the banks

coupled modeling of hydrogeochemical and electrical resistivity data for exploring the impact of recharge on subsurface contamination 1 the application of geophysical methods in particular electrical resistivity measurements may be useful for monitoring subsurface contamination however interpreting geophysical data without additional data and without considering the associated hydrogeochemical processes is challenging since the geophysical response is sensitive to not only heterogeneity in rock properties but also to the saturation and chemical composition of pore fluids we present an inverse modeling framework that incorporates the simulation of hydrogeochemical processes and time lapse electrical resistivity data and apply it to various borehole and cross borehole data sets collected in 2008 near the s 3 ponds at the u s department of energy s oak ridge integrated field research challenge site where efforts are underway to better understand freshwater recharge and associated contaminant dilution our goal is to show that the coupled hydrogeochemical geophysical modeling framework can be used to 1 develop a model that honors all the available data sets 2 help understand the response of the geophysical data to subsurface properties and processes at the site and 3 allow for the estimation of petrophysical parameters needed for interpreting the geophysical data we present a series of cases involving different data sets and increasingly complex models and find that the approach provides useful information about soil properties recharge related transport processes and the geophysical response spatial heterogeneity of the petrophysical model can be described sufficiently with two layers and its parameters can be estimated concurrently with the hydrogeochemical parameters for successful application of the approach the parameters of interest must be sensitive to the available data and the experimental conditions must be carefully modeled

detection of spatially limited high porosity layers using crosshole gpr signal analysis and full waveform inversion high permittivity layers related to high porosity layers or impermeable clay lenses can act as low velocity electromagnetic waveguides electromagnetic wave phenomena associated with these features are complicated not well known and not easy to interpret in borehole gpr data recently a novel amplitude analysis approach was developed that is able to detect continuous low velocity waveguides and their boundaries between boreholes by using maximum and minimum positions of the trace energy profiles in measured gpr data by analyzing waveguide models of different thickness dip extent permittivity and conductivity parameters we extend the amplitude analysis to detect spatially limited or terminated waveguides waveguides that show high amplitude elongated wave trains are most probably caused by a change in porosity rather than a change in clay content in a crosshole gpr data set from the boise hydrogeophysical research site two terminated wave guiding structures were detected using the extended amplitude analysis information gained from the amplitude analysis improved the starting model for full waveform inversion which imaged the lateral extent and thickness of terminated waveguides with high resolution synthetic data calculated using the inverted permittivity and conductivity models show similar amplitudes and phases as observed in the measured data which indicates the reliability of the obtained models neutron neutron logging data from three boreholes confirm the changes in porosity and indicate that these layers were high porosity sand units within low porosity poorly sorted sand and gravel units

hydrostratigraphic analysis of the made site with full resolution gpr and direct push hydraulic profiling 1 f ull resolution 3d ground penetrating radar gpr data were combined with high resolution hydraulic conductivity k data from vertical direct push dp profiles to characterize a portion of the highly heterogeneous macro dispersion experiment made site this is an important first step to better understand the influence of aquifer heterogeneities on observed anomalous transport statistical evaluation of dp data indicates non normal distributions that have much higher similarity within each gpr facies than between facies the analysis of gpr and dp data provides high resolution estimates of the 3d geometry of hydrostratigraphic zones which can then be populated with stochastic k fields the lack of such estimates has been a significant limitation for testing and parameterizing a range of novel transport theories at sites where the traditional advection dispersion model has proven inadequate citation dogan m r l van dam g c bohling j j butler jr and d w hyndman 2011 hydrostratigraphic analysis of the made site with full resolution gpr and direct push hydraulic profiling geophys res lett 38 l06405 doi 10 1029 2010gl046439

saline tracer visualized with three dimensional electrical resistivity tomography field scale spatial moment analysis 1 cross well electrical resistivity tomography ert was used to monitor the migration of a saline tracer in a two well pumping injection experiment conducted at the massachusetts military reservation in cape cod massachusetts after injecting 2200 mg l of sodium chloride for 9 hours ert data sets were collected from four wells every 6 hours for 20 days more than 180 000 resistance measurements were collected during the tracer test each ert data set was inverted to produce a sequence of 3 d snapshot maps that track the plume in addition to the ert experiment a pumping test and an infiltration test were conducted to estimate horizontal and vertical hydraulic conductivity values using modified moment analysis of the electrical conductivity tomograms the mass center of mass and spatial variance of the imaged tracer plume were estimated although the tomograms provide valuable insights into field scale tracer migration behavior and aquifer heterogeneity standard tomographic inversion and application of archie s law to convert electrical conductivities to solute concentration results in underestimation of tracer mass such underestimation is attributed to 1 reduced measurement sensitivity to electrical conductivity values with distance from the electrodes and 2 spatial smoothing regularization from tomographic inversion the center of mass estimated from the ert inversions coincided with that given by migration of the tracer plume using 3 d advective dispersion simulation the 3 d plumes seen using ert exhibit greater apparent dispersion than the simulated plumes and greater temporal spreading than observed in field data of concentration breakthrough at the pumping well

characterization of shallow karst using electrical resistivity imaging in a limestone mining area the guangxi area is famous for its high degree of karstification due to a long period of groundwater erosion and the development of fracture networks karst collapse appeared during the mining process and caused many environmental problems applying electrical resistivity imaging eri is the most cost effective method to study the characteristic of the subsurface karst environment in this area more than 24 km of eri profiles around a mining area is carried out to present the development of karst which will be used to evaluate the effects on the ground water and the surrounding environment the area represents a classical limestone rock which is of high quality and is used for cement production in this study the eri is used to determine the geometry of the karst range at depth the results are in good agreement with drilling experiments the eri survey provided near surface resistivity information which is very useful for establishing the geometry and the position of potential karst

imaging and quantifying salt tracer transport in a riparian groundwater system by means of 3d ert monitoring abstractdetermining groundwater flow paths of infiltrated river water is necessary for studying biochemical processes in the riparian zone but their characterization is complicated by strong temporal and spatial heterogeneity we investigated to what extent repeat 3d surface electrical resistance tomography ert can be used to monitor transport of a salt tracer plume under close to natural gradient conditions the aim is to estimate groundwater flow velocities and pathways at a site located within a riparian groundwater system adjacent to the perialpine thur river in northeastern switzerland our ert time lapse images provide constraints on the plume s shape flow direction and velocity these images allow the movement of the plume to be followed for 35 m although the hydraulic gradient is only 1 43 the ert time lapse images demonstrate that the plume s center of mass and its front propagate with velocities of 2 10 4 m s and 5 10 4 m s respectively these velocities are compatible with groundwate

electrical resistivity tomography of vadose water movement cross borehole electrical resistivity tomography ert was used to image the resistivity distribution before and during two infiltration experiments in both cases water was introduced into the vadose zone and the change in resistivity associated with the plume of wetted soil was imaged as a function of time the primary purpose of this work was to study the capabilities and limitations of ert to image underground structure and ground water movement in the vadose zone a secondary goal was to learn specifics of unsaturated flow in a complex geologic setting tomographs of electrical resistivity taken before infiltration image coarser well drained soils sands and gravels as more resistive zones whereas finer grained soils silts and clays which hold more water by capillarity are imaged as more conductive images of changes in resistivity during infiltration show growth of the water infiltration plume with time that is consistent with known geology in the ert images we see the effects of capillary barriers and infer differences between capillary driven flow through fine sediments and gravity driven flow through very permeable sediments images are consistent with numerical flow simulations using hydrological parameter values consistent with soil types inferred from well logs ert can be a useful tool to monitor movement of circuitous moisture fronts in a heterogeneous field setting that would go undetected by borehole measurements

formation process of the kuroshio large meander in 2004 1 formation process of the 2004 kuroshio large meander has been examined using a data assimilation and prediction system the small meander southeast of kyushu that occurred in december 2003 remains stationary until the next spring the vorticity analysis indicates that this small meander is maintained by a balance between the advection and the bottom pressure torque on the continental slope this balance is achieved as a result of reducing the advection by a westward propagating negative temperature anomaly originating in the wind stress field the small meander starts moving eastward around may 2004 when an anticyclonic eddy east of the tokara strait is intensified by coalescing of two anticyclonic eddies at that time a deep anticyclonic eddy is generated below the kuroshio by a cross frontal flow the deep anticyclonic eddy grows up during its eastward propagation then a southward flow in the eastern part of the eddy carries the kuroshio path offshore bringing about the large meander the eddy energetic analysis indicates that baroclinic instability is essentially responsible for this large meander formation the sensitivity analysis reveals that the small meander and the intensified anticyclonic eddy significantly affect the phase speed and the amplitude of the meander respectively it is also revealed that a slow phase speed and a large amplitude of the meander are regarded as conditions for the stationary large meander which is also applicable to the past large meanders in the 2004 large meander these conditions coexist by the stationary small meander staying until the intensified anticyclonic eddy triggers baroclinic instability

estimation of seepage rates in a losing stream by means of fiber optic high resolution vertical temperature profiling summary vertical temperature profiling in the river beds of losing streams has been shown to be useful in obtaining seepage rates we present a method for high resolution vertical temperature profiling in surface water sediments for detailed quantification of seepage flux over depth and time the method is based on fiber optic distributed temperature sensing in which temperature profiles along an optical fiber are obtained by making use of raman scattering an optical fiber was wrapped around a 2 in pvc tube and installed vertically within the streambed sediment the wrapping transfers the spatial resolution along the fiber of 1 m to a vertical resolution of about 5 mm the high resolution temperature profiler was tested at a losing reach of the swiss prealpine river thur resulting in a 20 day long temperature time series with a temporal resolution of 10 min the time series are analyzed by means of dynamic harmonic regression to obtain the diurnal contributions of the measured time series at all depths and time points the time for the diurnal temperature signal to reach the observation depth and the associated attenuation of the signal are calculated from the phase angles and amplitudes of the diurnal contributions the time shift results in an apparent celerity of diurnal temperature propagation which is converted into an apparent seepage rate by fitting the data to the analytical solution for convective conductive heat transfer in a semi infinite uniform one dimensional domain with a sinusoidal surface temperature the high spatial resolution allows the location of discontinuities in the river bed which would have remained undetected if temperature had been measured only at a few individual depths to be identified this is a particular strength of the fiber optic high resolution temperature profiler the time series also give evidence of sporadic high infiltration rates at times of high water tables

three dimensional simulation of gas and dust in io s pele plume abstract io s giant pele plume rises high above the moon s surface and produces a complex deposition pattern we use the direct simulation monte carlo dsmc method to model the flow of so2 gas and silicate ash from the surface of the lava lake into the umbrella shaped canopy of the plume and eventually onto the surface where the flow leaves black butterfly wings surrounded by a large red ring we show how the geometry of the lava lake from which the gas is emitted is responsible for significant asymmetry in the plume and for the shape of the red deposition ring by way of complicated gas dynamic interactions between parts of the gas flow arising from different areas in the lava lake we develop a model for gas flow in the immediate vicinity of the lava lake and use it to show that the behavior of ash particles of less than about 2 m in diameter in the plume is insensitive to the details of how they are introduced into the flow because they are coupled to the gas at low altitudes we simulate dust particles in the plume to show how particle size determines the distance from the lava lake at which particles deposit on the surface and we use this dependence to find a size distribution of black dust particles in the plume that provides the best explanation for the observed black fans to the east and west of the lava lake this best fit particle size distribution suggests that there may be two distinct mechanisms of black dust creation at pele and when two log normal distributions are fit to our results we obtain a mean particle diameter of 88 nm we also propose a mechanism by which the condensible plume gas might overlay black dust in areas where black coloration is not observed and compare this to the observed overlaying of pillanian dust by pele s red ring

using two and three dimensional georadar methods to characterize glaciofluvial architecture abstract the threat of pollution in the shallow subsurface has led to an increasing need to understand how complex heterogeneities in gravel aquifers influence groundwater transport to characterize these heterogeneities we have conducted extensive two dimensional 2 d and three dimensional 3 d ground penetrating radar gpr or georadar surveys in two quarries within the rhine valley of northeastern switzerland the quarries comprised gravel and sand deposited in a proglacial braided river system that followed the maximum wurm stage glaciation after the surveys the terrace walls beneath the two study sites were photographed as they were being excavated by combining information extracted from the 2 and 3 d georadar images with the outcrop photographs it was possible to correlate georadar facies with the various glaciofluvial architectural elements the dominant elements were scour pools formed at or near the confluences of two stream channels and horizontally bedded and massive gravel sheets deposited during moderate to high water flow conditions and exposed during low flow conditions architectural elements were generally elongated parallel to the mean flow directions of the ancient river system variations in the strike of their long axes reflected lateral and vertical changes in the local flow direction time slices showed structural trends not evident on 2 d georadar images and photographs data interpretation was quicker more complete and less ambiguous when georadar facies analyses were based on a combination of georadar vertical profiles and time slices than when based on georadar vertical profiles alone

heterogeneity patterns of quaternary glaciofluvial gravel bodies sw germany application to hydrogeology abstract the architecture of sedimentary bodies determines the heterogeneity of many aquifers thus for environmental risk assessment and quantification of clean up efficiencies determination of the spatial distribution of hydraulic properties is required in this study outcrop analogues of glaciofluvial gravel bed deposits are used for a process based analysis of sedimentary heterogeneities which in turn are transformed into hydraulic parameters three scales of heterogeneities are distinguished a the lithofacies scale is formed by unique transport and depositional processes that form the fundamental building blocks hydrofacies types b the depositional element scale shows distinct geometrical characteristics internal structure and bounding surfaces and determines the local distribution of lithofacies and hence the correlation structure of permeabilities c the architectural scale of gravel bodies is formed by the stacking of depositional elements which is controlled by the dynamics of aggrading paleofluvial systems comparison of numerous gravel pits in sw germany revealed three major architectural patterns of glaciofluvial gravel bodies that can be distinguished statistically by the preservation of depositional elements as well as the frequency of lithofacies types the facies analysis results in three conceptual facies models of proglacial river systems which are regionally classified as main intermediate and minor discharge types based on calculated and laboratory measured hydraulic properties of the various lithofacies types detailed outcrop wall maps were digitized into polygons of defined hydrofacies types by using the gis system arc info the two dimensional fields of hydraulic properties were then transferred into a numerical model of groundwater flow modeling results clearly illustrate that the three heterogeneity patterns of gravel bodies also have distinguishable hydraulic response characteristics

a new approach for time lapse data weighting in electrical resistivity tomography abstractapplications of time lapse inversion of electrical resistivity tomography allow monitoring variations in the subsurface that play a key role in a variety of contexts the inversion of time lapse data provides successive images of the subsurface properties showing the medium evolution image quality is highly dependent on the data weighting determined from the data error estimates however the quantification of errors in the inversion of time lapse data has not yet been addressed we have developed a methodology for the quantification of time lapse data error based on the analysis of the discrepancy between normal and reciprocal readings acquired at different times we applied the method to field monitoring data sets collected during the injection of heated water in a shallow aquifer we tested different error models to indicate that the use of an appropriate time lapse data error estimate yielded significant improvements in terms of imaging an adapted inversion weighting for time lapse data impl

field study of dispersion in a heterogeneous aquifer 4 investigation of adsorption and sampling bias the declining mass balance trend observed for bromide and three fluorobenzoate tracers during a natural gradient experiment at a site near columbus mississippi prompted investigations related to the reactivity of the tracers and the representativeness of the tracer samples obtained from multilevel samplers a laboratory soil column study indicated that adsorption of bromide during the field experiment was of the order of 20 and that up to 10 of the three fluorobenzoates was adsorbed the presence of iron oxides and kaolinite in the alluvial aquifer combined with the low groundwater ph of 4 8 produced geochemical conditions conducive to adsorption of the anionic tracers multilevel samplers mls used in the field experiment were evaluated by comparing bromide concentrations from the mls with water samples extracted from adjacent soil cores vertically averaged bromide concentrations for the mls were 21 lower than those for the cores a matrix diffusion process in conjunction with a natural tendency for preferential sampling from permeable regions in the heterogeneous alluvial sediments is proposed as an explanation for the apparent bias in the mls sample concentrations this process is shown to be qualitatively consistent with the tracer mass balance observed during the natural gradient experiment 14 refs 11more figs 8 tabs less

electrical characterization of non fickian transport in groundwater and hyporheic systems 1 recent work indicates that processes controlling solute mass transfer between mobile and less mobile domains in porous media may be quantified by combining electrical geophysical methods and electrically conductive tracers whereas direct geochemical measurements of solute preferentially sample the mobile domain electrical geophysical methods are sensitive to changes in bulk electrical conductivity bulk ec and therefore sample ec in both the mobile and immobile domains consequently the conductivity difference between direct geochemical samples and remotely sensed electrical geophysical measurements may provide an indication of mass transfer rates and mobile and immobile porosities in situ here we present 1 an overview of a theoretical framework for determining parameters controlling mass transfer with electrical resistivity in situ 2 a review of a case study estimating mass transfer processes in a pilot scale aquifer storage recovery test and 3 an example application of this method for estimating mass transfer in watershed settings between streams and the hyporheic corridor we demonstrate that numerical simulations of electrical resistivity studies of the stream hyporheic boundary can help constrain volumes and rates of mobile immobile mass transfer we conclude with directions for future research applying electrical geophysics to understand field scale transport in aquifer and fluvial systems subject to rate limited mass transfer

vadose zone flow model parameterisation using cross borehole radar and resistivity imaging cross borehole geoelectrical imaging in particular electrical resistivity tomography ert and transmission radar tomography can provide high resolution images of hydrogeological structures and in some cases detailed assessment of dynamic processes in the subsurface environment through appropriate petrophysical relationships these tools offer data suitable for parameterising and constraining models of groundwater flow this is demonstrated using cross borehole radar and resistivity measurements collected during a controlled vadose zone tracer test performed at a field site in the uk sherwood sandstone both methods show clearly the vertical migration of the tracer over a 200 h monitoring period by comparing first and second spatial moments of changes in moisture content predicted from a numerical simulation of vadose zone flow with equivalent statistics from two and three dimensional ert and cross borehole radar profiles the effective hydraulic conductivity is estimated to be approximately 0 4 m d such a value is comparable to field estimates from borehole hydraulic tests carried out in the saturated zone at the field site and provides valuable information that may be utilised to parameterise pollutant transport models of the site

variations of current path velocity and volume transport of the kuroshio in relation with the large meander abstract the variations of the kuroshio current path and their relations with current velocity volume transport and upstream position of the kuroshio are examined using sea level data after the long time non large meander nlm path during 1963 75 the kuroshio takes a large meander lm path during most of 1975 91 1975 80 1981 84 1986 88 and 1989 91 the study of these meanders confirms the description of the path of the kuroshio based on the three typical paths and the transitions between them with an exception being the 1981 84 lm path the formation and decay of the large meander are associated with velocity and position of the kuroshio in the tokara strait south of kyushu a small meander precursor of the large meander seems to be formed southeast of kyushu in relation with a temporary increase of kuroshio velocity and a northward shift of the kuroshio in the tokara strait an eastward propagation of the small meander leading to the lm formation is associated with remaining in the northe

borehole cylindrical noise during hole surface and hole hole resistivity measurements drilled boreholes generally are the only feasible means to access the subsurface for the emplacement of downhole electrodes for most hole hole and hole surface resistivity experiments however the very existence of the borehole itself creates the potential for significant noise due to the inevitable conductivity contrast that develops between the borehole walls and the formation borehole cylindrical noise develops whenever a current source is placed in a drilled borehole borehole geometries may range from nearly perfect cylinders to highly irregular rugose holes in consolidated rock to relatively minor collapsed disturbed zones in caving sediments boreholes in non caving formations generally are filled with artificial conductive materials to afford crucial electrical continuity between downhole electrodes and the borehole walls filled boreholes form cylindrically shaped heterogeneities that create significant noise due to preferential current flow up and down the conductive columns selected conditions are simulated with a finite difference model to illustrate the significance of borehole cylindrical noise on hole hole and hole surface mise a la masse electrical potentials near a current electrode mise a la masse electrical potentials measured during a field tracer experiment also are presented these measurements are used to illustrate significant errors may develop in the interpretation of apparent resistivity estimates out to a distance of several meters from the current source if borehole cylindrical noise is not recognized and accounted for in the analysis of electrical potential data

impact of heterogeneity bed forms and stream curvature on subchannel hyporheic exchange 1 advection through hyporheic zones hz consisting of heterogeneous channel bend streambed deposits and their equivalent homogenous medium was investigated using finite difference groundwater flow and transport simulations and forward particle tracking the top prescribed head boundary was varied in order to mimic various stream channel head distributions resulting from the presence of bed forms and channel curvature flux calculations show that heterogeneity causes significant additional hz flux compared to an equivalent homogenous medium however the major cause of hz flux is a spatially periodic sinusoidal head distribution along the boundary representing the effect of bed forms the additional influence of heterogeneity on the total channel bed exchange and the overall hz geometry are increased when boundary head sinusoidal fluctuation is more subdued we present dimensionless numbers that summarize these relationships heterogeneity s influence is further magnified by considering the effect of channel curvature on boundary heads the simulations illustrate the dynamic influence of heterogeneity on the hyporheic zone since the various head boundaries employed in our modeling efforts are a proxy for different surface water conditions and bed form states that may occur during a single flood furthermore we show that residence times total tracking times of particles originating from the streambed follow a lognormal distribution in the presence of heterogeneity residence times can decrease or they can increase compared to residence times for homogeneous conditions depending on the relative positions of the heterogeneities and the bed forms hence streambed heterogeneity and stream curvature factors often neglected in previous modeling efforts combine with bed form configuration to dynamically determine hz geometry fluxes and residence time distributions

time lapse seismic imaging using regularized full waveform inversion with a prior model which strategy full waveform inversion is an appealing technique for time lapse imaging especially when prior model information is included into the inversion workflow once the baseline reconstruction is achieved several strategies can be used to assess the physical parameter changes such as parallel difference two separate inversions of baseline and monitor data sets sequential difference inversion of the monitor data set starting from the recovered baseline model and double difference inversion of the difference data starting from the recovered baseline model strategies using syntheticmarmousi data sets we investigate which strategy should be adopted to obtain more robust and more accurate time lapse velocity changes in noise free and noisy environments this synthetic application demonstrates that the double difference strategy provides the more robust time lapse result in addition we propose a target oriented time lapse imaging using regularized full waveform inversion including a prior model and model weighting if the prior information exists on the location of expected variations this scheme applies strong prior model constraints outside of the expected areas of timelapse changes and relatively less prior constraints in the time lapse target zones in application of this process to the marmousi model data set the local resolution analysis performed with spike tests shows that the target oriented inversion prevents the occurrence of artefacts outside the target areas which could contaminate and compromise the reconstruction of the effective time lapse changes especially when using the sequential difference strategy in a strongly noisy case the target oriented prior model weighting ensures the same behaviour for both time lapse strategies the double difference and the sequential difference strategies and leads to a more robust reconstruction of the weak time lapse changes the double difference strategy can deliver more accurate time lapse variation since it can focus to invert the difference data however the double difference strategy requires a preprocessing step on data sets such as time lapse binning to have a similar source receiver location between two surveys while the sequential difference needs less this requirement if we have prior information about the area of changes the target oriented sequential difference strategy can be an alternative and can provide the same robust result as the doubledifference strategy

the nonlinear optimal triggering perturbation of the kuroshio large meander and its evolution in a regional ocean model abstractbased on the regional ocean modeling system roms and the conditional nonlinear optimal perturbation cnop method we explore the nonlinear optimal triggering perturbation of the kuroshio

new perspectives on the generation and maintenance of the kuroshio large meander abstractthe internal dynamical processes underlying the kuroshio large meander are investigated using a recently developed analysis tool multiscale window transform mwt and the mwt based canoni

tracking tracer motion in a 4 d electrical resistivity tomography experiment a new framework for automatically tracking subsurface tracers in electrical resistivity tomography ert monitoring images is presented using computer vision and bayesian inference techniques in the form of a kalman filter the trajectory of a subsurface tracer is monitored by predicting and updating a state model representing its movements observations for the kalman filter are gathered using the maximally stable volumes algorithm which is used to dynamically threshold local regions of an ert image sequence to detect the tracer at each time step the application of the framework to the results of 2 d and 3 d tracer monitoring experiments show that the proposed method is effective for detecting and tracking tracer plumes in ert images in the presence of noise without intermediate manual intervention

characterizing hydrological processes on loess slopes using electrical resistivity tomography a case study of the heifangtai terrace northwest china abstract from the perspective of engineering geology loess has long been considered as a homogeneous and porous material it is commonly believed that water penetrates loess via pores and in some cases causing mass movements however several researchers have expressed doubts about this mechanism as a cause of slope failures in loess and moreover the actual hydrological processes operating in loess deposits and their effect on slope failures have not been fully investigated here we present the results of an electrical resistivity survey of the heifangtai loess terrace in northwestern china designed to characterize the hydrological processes in loess slopes and their relationship with slope failures the heifangtai loess terrace is located on the fourth terrace of the yellow river and consists of 57 m thickness of aeolian loess 2d and 3d electrical resistivity tomography ert was used to monitor the movement of ground water before and after irrigation and rainfall events and the evolution of a sink hole in the toe of the landslide deposits our main findings are as follows 1 based on the 2d ert results the depth of infiltration into the thick unsaturated loess is not more than 5 m in the profile at the top of the landslide 2 electrical resistivity decreased as a result of water infiltration through sinkholes and this process can increase the soil water content and induce soil liquefaction which can eventually result in land sliding 3 landslide deposits block the groundwater drainage channels through the loess which results in the concentration of water in the toe of the landslide consequently groundwater together with rainfall triggers the failure of sinkholes or cracks which may induce a continuing process of new slope failures at the sites of past landslide

bimodality of the kuroshio abstract a barotropic ocean model is used to study the bimodal behavior of the kuroshio to the south of japan by considering the combined effects of the beta plane the kyushu coastal perturbation the izu ridge and the sw ne tilted coastline the two frequently observed meander patterns have been numerically verified as the two quasi steady solutions contained n the model the small meander state is identified as an upstream disturbance largely forced by the izu ridge its width decreases as the strength of the current increases the large meander state is forced by the presence of both the kyushu wedge and the izu ridge topography for small volume transports the large meander state behaves like the small meander state in that the meander width decreases as the current speed increases for large volume transports it behaves like a lee rossby wave in that the width of the meander increases as the current speed increases the birth of the large meander state occurs as a consequence of the ocean spin do

quantitative imaging of solute transport in an unsaturated and undisturbed soil monolith with 3 d ert and tdr electrical resistivity tomography ert has proved to be a valuable tool for imaging solute transport processes in the subsurface however a quantitative interpretation of corresponding ert results is constrained by a number of factors one such factor is the nonuniqueness of the ert inverse problem if no additional constraints are imposed in the vadose zone further problems arise from the general ambiguity of the imaged bulk electrical conductivity in terms of water content and solute concentration in this study we address these issues in detail for a solute tracer experiment conducted in an undisturbed unsaturated soil monolith where the tracer transport was monitored by means of 3 d smoothness constrained ert and time domain reflectometry tdr measurements the experimental design allowed the determination of solute tracer concentrations directly from imaged bulk electrical conductivity independent tdr data and effluent tracer concentrations provided a ground truth for the ert derived apparent convection dispersion equation transport parameters the apparent transport velocity calculated from the ert results was consistent with that based on tdr data and the sampled effluent independent of the degree of smoothness imposed in the ert inversion on the other hand the apparent dispersivity calculated from the ert results was larger than that estimated from tdr data but smaller than that estimated from the sampled effluent with the magnitude of deviations dependent on the degree of smoothing importantly no mass balance problems were observed in the ert results we believe that this is largely a consequence of the uniform application of the tracer as a front and of the configuration of the electrode array with respect to the main transport direction in conclusion the study demonstrates that ert can yield unprecedented quantitative information about local and column scale solute transport characteristics in natural soils

structure coupled joint inversion of geophysical and hydrological data abstractin groundwater hydrology geophysical imaging holds considerable promise for improving parameter estimation due to the generally high resolution and spatial coverage of geophysical data however inversion of geophysical data alone cannot unveil the distribution of hydraulic conductivity jointly inverting geophysical and hydrological data allows us to benefit from the advantages of geophysical imaging and at the same time recover the hydrological parameters of interest we have applied a coupling strategy between geophysical and hydrological models that is based on structural similarity constraints model combinations for which the spatial gradients of the inferred parameter fields are not aligned in parallel are penalized in the inversion this structural coupling does not require introducing a potentially weak unknown and nonstationary petrophysical relation to link the models the method was first tested on synthetic data sets and then applied to two combinations of geophysical hydrolog

evaluation of longitudinal dispersivity estimates from simulated forced and natural gradient tracer tests in heterogeneous aquifers 1 we simulate three types of forced gradient tracer tests converging radial flow unequal strength two well and equal strength two well and natural gradient tracer tests in multiple realizations of heterogeneous two dimensional aquifers with a hydraulic conductivity distribution characterized by a spherical variogram we determine longitudinal dispersivities l by analysis of forced gradient test breakthrough curves at the pumped well and by spatial moment analysis of tracer concentrations during the natural gradient tests results show that among the forced gradient tests a converging radial flow test tends to yield the smallest l an equal strength two well test tends to yield the largest l and an unequal strength two well test tends to yield an intermediate value this finding is qualitatively explained by considering the aquifer area sampled by a particular test a converging radial flow test samples a small area and thus the tracer undergoes a low degree of spreading and mixing an equal strength two well test samples a much larger area so the tracer is spread and mixed to a greater degree results also suggest that if the distance between the tracer source well and the pumped well is short relative to the lengths over which velocity is correlated then the l estimate can be highly dependent on local heterogeneities in the vicinity of the wells finally results indicate that l estimated from forced gradient tracer tests can significantly underestimate the l needed to characterize solute dispersion under natural gradient flow only a two well tracer test with a large well separation in an aquifer with a low degree of heterogeneity can yield a value of l that characterizes natural gradient tracer spreading this suggests that a two well test with a large well separation is the preferred forced gradient test for characterizing solute dispersion under natural gradient flow

a clathrate reservoir hypothesis for enceladus south polar plume we hypothesize that active tectonic processes in the south polar terrain of enceladus the 500 kilometer diameter moon of saturn are creating fractures that cause degassing of a clathrate reservoir to produce the plume documented by the instruments on the cassini spacecraft advection of gas and ice transports energy supplied at depth as latent heat of clathrate decomposition to shallower levels where it reappears as latent heat of condensation of ice the plume itself which has a discharge rate comparable to old faithful geyser in yellowstone national park probably represents small leaks from this massive advective system

a salt tracer test monitored with surface ert to detect preferential flow and transport paths in fractured karstified limestones in hard rock aquifers fractured zones constitute adequate drinking water exploitation areas but also potential contamination paths one critical issue in hydrogeological research is to identify characterize and monitor such fractured zones at a representative scale a tracer test monitored with surface electrical resistivity tomography ert could help by delineating such preferential flow paths and estimating dynamic properties of the aquifer however multiple challenges exist including the lower resolution of surface ert compared with crosshole ert the finite time that is needed to complete an entire data acquisition and the strong dilution effects we conducted a natural gradient salt tracer test in fractured limestones to account for the high transport velocity we injected the salt tracer continuously for four hours at a depth of 18 m we monitored its propagation with two parallel ert profiles perpendicular to the groundwater flow direction concerning the data acquisition we always focused

neutrally buoyant tracers in hydrogeophysics field demonstration in fractured rock electrical and electromagnetic methods are extensively used to map electrically conductive tracers within hydrogeologic systems often the tracers used consist of dissolved salt in water leading to a denser mixture than the ambient formation water density effects are often ignored and rarely modeled but can dramatically affect transport behavior and introduce dynamics that are unrepresentative of the response obtained with classical tracers e g uranine we introduce a neutrally buoyant tracer consisting of a mixture of salt water and ethanol and monitor its movement during push pull experiments in a fractured rock aquifer using ground penetrating radar our results indicate a largely reversible transport process and agree with uranine based push pull experiments at the site which is in contrast to results obtained using dense saline tracers we argue that a shift toward neutrally buoyant tracers in both porous and fractured media would advance hydrogeophysical research and enhance its utility in hydrogeology

mapping the architecture of glaciofluvial sediments with three dimensional georadar three dimensional 3 d ground penetrating radar georadar mapping offers new opportunities for determining the geometries and facies of surficial sedimentary units to investigate the potential of this high resolution technique and at the same time study the architecture of quaternary glaciofluvial deposits georadar data have been collected on a dense grid established across a sequence of braided river gravels and sands in northeastern switzerland results of this survey are striking 3 d images that provide many more details and much more reliable information on the heterogeneities of the shallow underground than are afforded by conventional georadar profile data continuous subhorizontal and oblique reflections can be traced throughout vertical sections and horizontal slices of the georadar data block to a depth of approx 15 m clearly defined are the dominant flow direction of the ancient braided river system the boundaries between different sedimentary facies and the level of the ground water table trough fill sediments and subhorizontal channel deposits observed on 7 m high quarry walls can be followed confidently in the subsurface the orientation shape and size of the troughs and the strike and dip of the cross bedding are all well resolved

stochastic inversion of tracer test and electrical geophysical data to estimate hydraulic conductivities 1 quantifying the spatial configuration of hydraulic conductivity k in heterogeneous geological environments is essential for accurate predictions of contaminant transport but is difficult because of the inherent limitations in resolution and coverage associated with traditional hydrological measurements to address this issue we consider crosshole and surface based electrical resistivity geophysical measurements collected in time during a saline tracer experiment we use a bayesian markov chain monte carlo mcmc methodology to jointly invert the dynamic resistivity data together with borehole tracer concentration data to generate multiple posterior realizations of k that are consistent with all available information we do this within a coupled inversion framework whereby the geophysical and hydrological forward models are linked through an uncertain relationship between electrical resistivity and concentration to minimize computational expense a facies based subsurface parameterization is developed the bayesian mcmc methodology allows us to explore the potential benefits of including the geophysical data into the inverse problem by examining their effect on our ability to identify fast flowpaths in the subsurface and their impact on hydrological prediction uncertainty using a complex geostatistically generated two dimensional numerical example representative of a fluvial environment we demonstrate that flow model calibration is improved and prediction error is decreased when the electrical resistivity data are included the worth of the geophysical data is found to be greatest for long spatial correlation lengths of subsurface heterogeneity with respect to wellbore separation where flow and transport are largely controlled by highly connected flowpaths

two dimensional joint inversions of cross hole resistivity data and resolution analysis of combined arrays in this study a new two dimensional inversion algorithm was developed for the inversion of cross hole direct current resistivity measurements in the last decades various array optimisation methods were suggested for resistivity tomography however researchers have still collected data by using classical electrode arrays in most cross hole applications therefore we investigated the accuracy of both the individual and the joint inversion of the classical cross hole arrays by using both synthetic and field data with the developed algorithm we showed that the joint inversion of bipole bipole pole bipole bipole pole and pole tripole electrode arrays gives inverse solutions that are closer to the real model than the individual inversions of the electrode array datasets for the synthetic data inversion the model resolution matrix of the suggested arrays was used to analyse the inversion results this model resolution analysis also showed the advantage of the joint inversion of bipole bipole pole bipole bipole pole and pole tripole arrays we also used sensitivity sections from each of the arrays and their superpositions to explain why joint inversion gives better resolution than the any individual inversion result

response of storm tracks to bimodal kuroshio path states south of japan abstracta large meridional shift of the sea surface temperature front occurs off the south coast of japan associated with transitions between the large meander and straight paths of the kuroshio most extratropical cyclones generated in winter near the kuroshio in the east china sea pass through the region where the kuroshio takes either the meander or the straight path to examine whether such cyclones change their tracks and intensities according to the two states of the path a new dataset of winter cyclone tracks derived from surface weather charts from the period 1969 70 2008 09 was produced the composite analysis of cyclone tracks with respect to the meander and straight path states reveals the following the cyclone track axis for the meander path state is located away from the south coast of japan with a dispersive tendency while that for the straight path state is attached to the south coast with a long extending feature a difference in track between these two states also occurs to the east of

inversion of time lapse electrical resistivity imaging data for monitoring infiltration monitoring hydrologic processes in the vadose zone is of great importance in developing management strategies for groundwater resources flow and transport behavior in variably saturated media control the rate at which and path along which fluids or contaminants reach groundwater aquifers electrical resistivity imaging eri is sensitive to changes in the subsurface conductivity structure which is highly dependent on the water saturation distribution in the vadose zone time lapse eri therefore has been widely used for environmental and hydrologic monitoring experiments

dynamics of the kuroshio large meander two layer model abstract a simple two layered in outflow model is studied to explain the peculiarity of the kuroshio path the geometry south of japan with a length scale l and the characteristic velocity u of the kuroshio give an important parameter 2 u l the kuroshio can take two kinds of paths for a given value of multiple equilibria one is straight path and the other a meandering path the selection of a path the selection of a path in a multiple equilibrium state depends upon the history of the parameter the hysteresis phenomenon the combined effect of horizontal viscosity along the coast and the inclination of the coastline are essential factors which control the kuroshio path as well as an increase in the coastline inclination increases the effect of horizontal viscosity along the coast where a western boundary layer is formed due to the effect of an increase in the viscous effect along the coast makes a straight path possible when the inlet velocity is small the effect of stratification i

imaging and characterisation of subsurface solute transport using electrical resistivity tomography ert and equivalent transport models abstract we assess the usefulness of electrical resistivity tomography ert in imaging and characterising subsurface solute transport in heterogeneous unconfined aquifers a field tracer experiment was conducted at the krauthausen test site germany the spatial and temporal evolution of the injected nabr solute plume was monitored in a 2d ert image plane located downstream of the injection well for 90 days since ert maps changes in bulk electrical conductivity the reconstructed images at selected time intervals are first converted to solute concentration maps by postulating a linear relation the concentration maps are then analysed using an equivalent convection dispersion model cdm which conceptualises the aquifer as a homogeneous medium with a uniform mean flow velocity as demonstrated by associated synthetic model studies ert resolution in terms of recovered equivalent dispersivities is limited due to spatial smoothing inherent to the imaging algorithm since for heterogeneous media local concentrations within the plume deviate from those predicted by the equivalent cdm we also interpret the ert derived pixel breakthrough curves in terms of an equivalent stream tube model stm the stm represents transport in the aquifer by a set of 1d convection dispersion processes allowing the degree of mixing and the heterogeneity of transport within the plume to be quantified we believe that the observed tracer plume is satisfactorily described by the equivalent cdm probably because the tracer plume was small relative to the heterogeneity scale of the aquifer even though application of the stm revealed some deviation from the ideal homogeneous case the equivalent dispersivity in the stm matches the longitudinal dispersivity of the cdm closely consistent with predominantly homogeneous mixing however the stm analysis illustrates how ert results can be used to quantify the variability of parameters relevant to flow and transport in heterogeneous aquifers

water content dynamics at plot scale comparison of time lapse electrical resistivity tomography monitoring and pore pressure modelling abstract physically based dynamic modelling of shallow landslide susceptibility rests on several assumptions and simplifications however the applicability of physically based models is only rarely tested in the field at the appropriate scale this paper presents results of a spray irrigation experiment conducted on a plot of 100 m2 on an alpine slope susceptible to shallow landsliding infiltrating precipitation applied at a constant rate 27 5 mm h for 5 3 h was monitored by means of 2d time lapse electrical resistivity tomography combined with time domain reflectometry sensors installed at various depths in addition regolith characteristics were assessed by dynamic cone penetration tests using a light weight cone penetrometer the spray irrigation experiment resulted in a vertically progressing wetting front to a depth of 80 100 cm below that the unconsolidated material was already saturated by rainfall in the previous days the observed mean resistivity reduction attributed to infiltrating water during irrigation was scaled to pressure head mean variations in pore pressure were reproduced by a linear diffusion model also used in physically based dynamic landslide susceptibility modelling sensitive parameters hydraulic conductivity and specific storage were tested over selected value ranges and calibrated calibrated parameter values are within published and experimentally derived ranges the results of the comparison of observations and model results suggest that the model is capable of reproducing mean changes of pore pressure at a suitable scale for physically based modelling of shallow landslide susceptibility however small scale variations in pore pressure that may facilitate the triggering of shallow landslides are not captured by the model

moment inference from tomograms 1 time lapse geophysical tomography can provide valuable qualitative insights into hydrologic transport phenomena associated with aquifer dynamics tracer experiments and engineered remediation increasingly tomograms are used to infer the spatial and or temporal moments of solute plumes these moments provide quantitative information about transport processes e g advection dispersion and rate limited mass transfer and controlling parameters e g permeability dispersivity and rate coefficients the reliability of moments calculated from tomograms is however poorly understood because classic approaches to image appraisal e g the model resolution matrix are not directly applicable to moment inference here we present a semi analytical approach to construct a moment resolution matrix based on 1 the classic model resolution matrix and 2 image reconstruction from orthogonal moments numerical results for radar and electrical resistivity imaging of solute plumes demonstrate that moment values calculated from tomograms depend strongly on plume location within the tomogram survey geometry regularization criteria and measurement error

fluid migration in the vadose zone from 3 d inversion of resistivity monitoring data the movement of a small plume of fresh water through the vadose zone was monitored using surface resistivity tomography and pole pole potential measurements sets of potential measurements on a square grid at several times throughout the experiment show gradual progressive and systematic development of low resistivity zones that are inferred to be loci of fluid concentration a procedure for inverting percentage changes in potentials is developed here and used to map maximum potential changes of 13 into resistivity decreases of up to 40 through 3 d resistivity inversion the resulting patterns are complex with both resistivity increases and decreases needed to match the observed data the resistivity reductions show a spatial connection to the plume s source and are suggestive of the fluid migration resistivity increases generally appear to form rims surrounding the decreases and may be artifacts of the inversion process however some isolated increases in the surface layer may be caused by evapora

roles of mesoscale eddies in the kuroshio paths a high resolution ocean general circulation model is developed to simulate connections between the kuroshio path variations and mesoscale eddy activities as realistically as possible the climatological mean of the modeled kuroshio takes a nearshore nonlarge meander path it is found that the model is capable of simulating two types of nonlarge meander state and a possible version of the large meander state the offshore nonlarge meander is generated through interaction between the kuroshio and an anticyclonic eddy the large meander occurs just after significant intensification of the anticyclonic kuroshio recirculation successive intrusion of anticyclonic eddies from the upstream region is responsible for this process those anticyclonic eddies are advected by the kuroshio from the region northeast of luzon island and increase the upstream kuroshio volume transport on an interannual time scale the cyclonic eddies propagating from the kuroshio extension region on the other hand weaken the kuroshio meander after the merger the kuroshio path variations south of japan thus seem to be closely related to eddy activities in the subtropical gyre system

curtain eruptions from enceladus south polar terrain observations of the south pole of the saturnian moon enceladus revealed large rifts in the terrain that were found to be the sources of the observed jets of water vapour now it is shown that much of the eruptive activity can be explained by broad curtain like eruptions many of which were probably misinterpreted previously as discrete jets images taken by the cassini probe have revealed large fractures bounded by rifts towards the south pole of saturn s moon enceladus these features popularly known as tiger stripes reach higher temperatures than their surroundings and are thought to be the sources of observed jets of water vapour and icy particles joseph spitale et al compare cassini images with simulated curtains of material erupting from enceladus south polar terrain to produce detailed maps of the emissions at various times much of the eruptive activity can be explained by broad curtain like eruptions many of which were probably misinterpreted previously as discrete jets phantom jets in the synthesized curtains correspond closely to regions of enhanced brightness in the cassini images observations of the south pole of the saturnian moon enceladus revealed large rifts in the south polar terrain informally called tiger stripes named alexandria baghdad cairo and damascus sulci these fractures have been shown to be the sources of the observed jets of water vapour and icy particles1 2 3 4 and to exhibit higher temperatures than the surrounding terrain5 6 subsequent observations have focused on obtaining close up imaging of this region to better characterize these emissions recent work7 examined those newer data sets and used triangulation of discrete jets3 to produce maps of jetting activity at various times here we show that much of the eruptive activity can be explained by broad curtain like eruptions optical illusions in the curtain eruptions resulting from a combination of viewing direction and local fracture geometry produce image features that were probably misinterpreted previously as discrete jets we present maps of the total emission along the fractures rather than just the jet like component for five times during an approximately one year period in 2009 and 2010 an accurate picture of the style timing and spatial distribution of the south polar eruptions is crucial to evaluating theories for the mechanism controlling the eruptions

investigation of seawater intrusion in the dibdibba aquifer using 2d resistivity imaging in the area between al zubair and umm qasr southern iraq electrical resistivity surveying for delineating seawater intrusion was performed in the dibdibba aquifer in the area between the cities of al zubair safwan and al zubair umm qasr in the vicinity of khor al zubair channel basrah governorate southern iraq fourteen 2d resistivity profiles with a total length of 14 km were collected in the study area the resistivity sections were compared with lithological data extracted from 11 boreholes thirty nine groundwater samples were collected within the area and analyzed for chemical constituents internal hydrogeological reports and unpublished studies were also evaluated results reveal the existence of three major resistivity layers ranging from 0 1 to 130 m at various depths and locations the first layer has very low electrical resistivity 0 1 5 m representing a layer saturated with saltwater intruded from khor al zubair channel the second layer shows resistivity in the range of 5 130 m attributed to a transition zone and an unaffected zone saturated with brackish groundwater the last resistivity layer 3 m represents coarse grain sediments saturated with saline groundwater furthermore a hard clay bed jojab appears with a resistivity of 3 7 m in all 2d imaging lines within a depth of 20 28 m electrical conductivity ec measurements from seven wells collected in 2014 and 2016 show a positive ec difference increasing landward with an average increase of 1927 s cm in addition six chemical relationships na cl ca mg hco3 so4 so4 hco3 so4 cl mg ca and cl hco3 co3 are used to detect the source of salinity in groundwater this study proves that extensive use of high resolution 2d imaging sections alongside lithological and hydrogeological data can serve as a useful tool to delineate the boundaries between aquifers identify hydraulic boundaries between groundwater with different salinities and allocate hard clay layers between the upper and lower dibdibba aquifer in general the combination of 2d imaging and hydrochemistry enables conceptualization of the hydrogeological situation in the subsurface and characterization of the salinity source here seawater intrusion in the study area there have been no studies published so far on the characteristics of saltwater intrusion in the study area and this study is considered to be important for monitoring and studying the intrusion and regression of seawater

a tracer test in a shallow heterogeneous aquifer monitored via time lapse surface electrical resistivity tomography we illustrate a case study of a saline tracer test in a shallow highly heterogeneous aquifer monitored by means of surface time lapse ert the test was aimed at identifying the system s hydraulic properties some of the expected limitations of the method particularly caused by the strong decrease in ert resolution with depth and the consequent problems with mass balance and moment calculation could be partly balanced by the use of direct measurements of groundwater electrical conductivity and tracer concentration at one selected location the vast heterogeneity of the system ranging in lithology from clay to gravel at a scale of meters to tens of meters reflects itself in the tracer migration and distribution over time the tracer is trapped in the low permeability regions and from these it is slowly released over time high resolution surface ert proves effective at picturing this system behavior over time the extreme heterogeneity is also a challenge in the attempt to translate bulk electrical

four dimensional electrical conductivity monitoring of stage driven river water intrusion accounting for water table effects using a transient mesh boundary and conditional inversion constraints this paper describes and demonstrates two methods of providing a priori information to the surface based time lapse three dimensional electrical resistivity tomography ert problem for monitoring stage driven or tide driven surface water intrusion into aquifers first a mesh boundary is implemented that conforms to the known location of the water table through time thereby enabling the inversion to place a sharp bulk conductivity contrast at that boundary without penalty second a nonlinear inequality constraint is used to allow only positive or negative transient changes in ec to occur within the saturated zone dependent on the relative contrast in fluid electrical conductivity between surface water and groundwater a 3 d field experiment demonstrates that time lapse imaging results using traditional smoothness constraints are unable to delineate river water intrusion the water table and inequality constraints provide the inversion with the additional information necessary to resolve the spatial extent of river water intrusion through time

single hole gpr reflection imaging of solute transport in a granitic aquifer 1 identifying transport pathways in fractured rock is extremely challenging as flow is often organized in a few fractures that occupy a very small portion of the rock volume we demonstrate that saline tracer experiments combined with single hole ground penetrating radar gpr reflection imaging can be used to monitor saline tracer movement within mm aperture fractures a dipole tracer test was performed in a granitic aquifer by injecting a saline solution in a known fracture while repeatedly acquiring single hole gpr sections in the pumping borehole located 6 m away the final depth migrated difference sections make it possible to identify consistent temporal changes over a 30 m depth interval at locations corresponding to fractures previously imaged in gpr sections acquired under natural flow and tracer free conditions the experiment allows determining the dominant flow paths of the injected tracer and the velocity 0 4 0 7 m min of the tracer front

cassini observes the active south pole of enceladus cassini has identified a geologically active province at the south pole of saturn s moon enceladus in images acquired by the imaging science subsystem iss this region is circumscribed by a chain of folded ridges and troughs at 55 s latitude the terrain southward of this boundary is distinguished by its albedo and color contrasts elevated temperatures extreme geologic youth and narrow tectonic rifts that exhibit coarse grained ice and coincide with the hottest temperatures measured in the region jets of fine icy particles that supply saturn s e ring emanate from this province carried aloft by water vapor probably venting from subsurface reservoirs of liquid water the shape of enceladus suggests a possible intense heating epoch in the past by capture into a 1 4 secondary spin orbit resonance

electrical monitoring of saline tracers to reveal subsurface flow pathways in a flat ditch drained field abstract time lapse electrical resistivity imaging eri combined with salt tracers can enhance our understanding of subsurface flow and transport in ditch drained agroecosystems in a nearly level field adjacent to a drainage ditch we installed 192 electrodes in a 72 m2 plot along with five hydrometric stations to enable time lapse eri monitoring during storms immediately prior to a wintertime rainstorm we applied 5 kg of kbr to a shallow trench located roughly 11 m upgradient from the ditch antecedent conditions prior to the storm were wet assuring a hydrologically connected state that favored tracer dissolution and movement in the subsurface we monitored the evolution of the tracer plume with eri over a seven day period four dimensional 4d delineation of precipitation and tracer transport using time lapse eri showed that the tracer plume moved preferentially downward through a discontinuity in the argillic horizon within the first 57 hrs over the following 79 hrs the tracer plume exhibited steady lateral movement towards the drainage ditch within a more permeable sandy horizon situated just below the argillic a spatial moment analysis of logarithmic changes in conductivity in the sand layer revealed seepage velocities ranging from 0 0027 to 0 0482 m d 1 these values were positively correlated with hydraulic gradients suggesting laminar flow processes typical of sandy aquifers increasing groundwater velocities with hydraulic gradients suggest that solute transfers from groundwater to ditch are likely to be faster in storms especially during wet periods even so predominantly slow lateral transport within the sandy horizon even during storms indicates that critical source areas of pollutant loss are likely within a few meters of the ditch

time variability of the enceladus plumes orbital periods decadal periods and aperiodic change the enceladus plumes vary on a number of timescales tidal stresses as enceladus revolves in its eccentric orbit lead to a periodic diurnal variation in the mass and velocity of solid particles in the plume tidal stresses associated with an orbital resonance with dione lead to a periodic decadal variation aperiodic variations occur on time scales of months and may be due to ice buildup and flow of the walls of the fissures that connect the ocean to the surface we document these variations using all the relevant data taken by the iss instrument from 2005 to 2017 key questions now include how a 5 peak to peak variation in orbital eccentricity which itself is only 0 0045 could lead to a 2 fold decadal variation in plume properties another question is how the plumes stay open if ice builds up every month and clogs the vents other questions include why the solid particles exit the vents several times slower than the gas and why the speeds vary inversely with the mass of the plumes the cassini data are in but the modeling has just begun

rate limited mass transfer or macrodispersion which dominates plume evolution at the macrodispersion experiment made site we present a model of solute transport that explains the large scale behavior of the solute tracer test plumes at the macrodispersion experiment made site as the result of advection and rate limited mass transfer between mobile and small scale immobile domains this model does not consider the process of dispersion and yet provides an alternative explanation of the evolution of the observed concentration profiles compared to the macrodispersion model the mass transfer model better represents the change in mobile dissolved mass with time the peak of the concentration profile and the profile asymmetry specifically unlike the macrodispersion model the mass transfer model explains the facts that the observed mass of the plume was greater than the injected mass in early snap shots of the plume and less than the injected mass at late times we suggest that the injected mass advects through the mobile domain and diffuses into and out of the immobile domain the immobile domain consists of a combination of low permeability zones on the scale of centimeters to decimeters the darcy scale immobile domain and intragranular porosity dead end pores and surface sorption the pore scale immobile domain we suggest that the mobile domain was sampled preferentially when water was extracted therefore at early times relatively clean water in the immobile domain was not sampled and incorrectly assumed to contain high solute concentrations similarly the mass at late times was underestimated because solute trapped in the pore scale immobile domain was not extracted during sampling and therefore ignored the combination of advection and slow mass transfer is consistent with the fact that the peak of the plume migrated only 5 m by the termination of the experiment as well as the different behavior of bromide and tritium tracers

response of extratropical cyclone activity to the kuroshio large meander in northern winter 1 we examined possible responses of cyclone activities to the bimodal path states of the kuroshio current i e large meander lm and non lm nlm by using the long term reanalysis data and the 20th century hindcast experiment of a high resolution atmosphere ocean coupled model compared with a seasonal mean cyclone track frequency for the lm and nlm periods a primary cyclone track shifts southward in association with the meander of kuroshio current composite analyses of the hindcast experiment showed remarkable atmospheric responses accompanying the kuroshio lm the kuroshio lm causes a decrease in latent heat flux in the south of japan and a southward shift of the near surface baroclinic zone distinctive decreases in thermodynamic fluxes inhibit the rapid development of cyclones in the meander region eventually inducing positive sea level pressure anomalies downstream from that region

time lapse imaging of saline tracer transport in fractured rock using difference attenuation radar tomography 1 accurate characterization of fractured rock aquifer heterogeneity remains one of the most challenging and important problems in groundwater hydrology we demonstrate a promising strategy to identify preferential flow paths in fractured rock using a combination of geophysical monitoring and conventional hydrogeologic tests cross well differenceattenuation ground penetrating radar was used to monitor saline tracer migration in an experiment at the u s geological survey fractured rock hydrology research site in grafton county new hampshire radar data sets were collected every 10 min in three adjoining planes for 5 hours during each of 12 tracer tests an innovative inversion method accounts for data acquisition times and temporal changes in attenuation during data collection the inverse algorithm minimizes a combination of two functions the first is the sum of weighted squared data residuals second is a measure of solution complexity based on an a priori space time covariance function subject to constraints that limit radarattenuation changes to regions of the tomograms traversed by high difference attenuation ray paths the time series of tomograms indicate relative tracer concentrations and tracer arrival times in the image planes from these we infer the presence and location of a preferential flow path within a previously identified zone of transmissive fractures these results provide new insights into solute channeling and the nature of aquifer heterogeneity at the site index terms 0910 exploration geophysics data processing 0915 exploration geophysics downhole methods 1829 hydrology groundwater hydrology 1832 hydrology groundwater transport 1894 hydrology instruments and techniques keywords radar tomography fractured rock ground penetrating radar geophysics hydrogeophysics

dynamics of kuroshio path variations in a high resolution general circulation model 1 a long lived 2 year typical large meander lm path of the kuroshio is reproduced in a high resolution general circulation model gcm simulation with realistic topography and the life cycle formation maintenance and disappearance of the lm is studied the formation of the lm is triggered by a pair of upper layer anticyclonic and cyclonic eddies on the kuroshio with the cyclonic one on the downstream side upon reaching the western side of the shikoku basin south of japan these anomalies induce a lower layer anticyclonic eddy they enhance each other while they are carried eastward by the kuroshio specifically the southward flow on the eastern side of the lower anticyclonic eddy carries the upper cold cyclonic eddy offshore resulting in the southward deflection of the kuroshio path large meander these processes can be understood as a growth of baroclinic instability a stationary lm is established when the westward tendency caused by the beta effect owing to the large meridional displacement counterbalances the eastward tendency caused by the combination of advection and vortex induction owing to the curvature of the kuroshio path large scale disturbances from the upstream tend to strengthen the lm through baroclinic energy conversion in contrast small scale disturbances from the upstream grow locally along the meandering kuroshio front through baroclinic energy conversion they extract cold waters from the cold cyclonic eddy of the lm as they flow away to the east the horizontal extent of the cold cyclonic eddy is reduced and the meander is carried eastward since the advection effect dominates over the beta effect that weakens as a result of the smaller meridional extent

a numerical study of the kuroshio south of japan abstract a numerical model is used to study the interaction of the kuroshio with boundary constraints south of japan the model consists of two layers with the lower layer inert and is both nonlinear and quasi geostrophic the boundary constraints are highly idealized the kyushu peninsula and its adjacent continental shelf have the form of a v shaped wedge on an otherwise rectilinear coastline the izu ridge is represented as a square island solutions almost always form a meander downstream from kyushu the dynamics of meander formation involve the interaction of a rossby lee wave generated by the kyushu peninsula and a westward disturbance forced by the izu ridge three different quasi steady paths have been identified the first path has a meander between kyushu and the izu ridge passes to the north of the ridge and is associated with a current of low volume transport the second path has a large meander between kyushu and the izu ridge passes to the south of the izu ridge and always occurs when

spatially distributed characterization of hyporheic solute transport during baseflow recession in a headwater mountain stream using electrical geophysical imaging summary the transport of solutes along hyporheic flowpaths is recognized as central to numerous biogeochemical cycles yet our understanding of how this transport changes with baseflow recession particularly in a spatially distributed manner is limited we conducted four steady state solute tracer injections and collected electrical resistivity data to characterize hyporheic transport during seasonal baseflow recession in the h j andrews experimental forest oregon usa we used temporal moment analysis of pixels generated from inversion of electrical resistivity data to compress time lapse data into descriptive statistics mean arrival time temporal variance and temporal skewness for each pixel a spatial visualization of these temporal moments in the subsurface at each of five 2 d transects perpendicular to the stream was interpreted to inform transport processes as baseflow recession progressed we found increasing first arrival times persistence mean arrival time temporal variance and coefficient of variation and decreasing skewness these trends suggest that changes in hydrologic forcing alter the relative influence of transport phenomena e g advection vs other transport processes such as dispersion along flowpaths spatial coverage obtained from electrical resistivity images allowed for qualitative comparison of spatial patterns in temporal moments both at an individual cross section as well as between cross sections we found that geomorphologic controls e g bedrock confinement vs gravel wedge deposits resulted in different distributions and metrics of hyporheic transport results of this study provide further evidence that hyporheic transport is highly variable both in space and through the baseflow recession period geophysical images differentiate advection dominated flowpaths from those that are more affected by other transport processes e g dispersion mobile immobile exchange

application of singular vector analysis to the kuroshio large meander 1 singular vector analysis is applied to the formation of the kuroshio large meander south of japan we use a simulation run of an ocean general circulation model ogcm in which a large meander occurs as the background state singular vectors are calculated by the lanczos method in which the tangent linear and adjoint models of the ogcm are used we apply an incremental correction approach for setting up the initial perturbation and averaging for the final norm in order to get modes reflecting nonlinear physics by filtering out high frequency variations the perturbation extracted as the leading right singular vector affects the formation of the large meander most if it is set to the background state two months before when the perturbation is added it enhances an anticyclonic eddy southeast of kyushu in the upper layer which induces downwelling north of it and develops an anticyclonic eddy in the deep layer the anticyclonic eddy produces a cold anomaly at the downstream edge and produces baroclinic instability there resulting in further development of the large meander in contrast the anticyclonic eddy in the deep layer is weakened when the perturbation is subtracted the development of the cold anomaly in the deep layer is delayed and consequently the meander is not so well developed thus singular vector analysis reveals the role of the anticyclonic eddy approaching southeast of kyushu in the upper layer and indicates the importance of the anticyclonic eddy in the deep layer

cross borehole resistivity tomography electrical resistivity tomography ert is a method for determining the electrical resistivity distribution in a volume from discrete measurements of current and voltage made within the volume or on its surface we have developed an ert algorithm that is an iterative modified least squares inversion based on a finite element forward solution of laplace s equation we report the results of tests on this algorithm designed to determine how resistance measurements made from two boreholes may be used to image the resistivity distribution between them a number of simple but geophysically significant structures are modeled these include a single isolated block anomaly two layers a thin isolated continuous layer and a vertical band the main features of most resistivity models were identifiable in the reconstructions limited data accuracy and noise were simulated and found to cause a deterioration of the image however even with measurements of only one significant figure accuracy the algorithm converg

the dynamics of error growth and predictability in a model of the gulf stream part i singular vector analysis abstract the recently developed ideas of generalized linear stability theory for dynamical systems are applied to time evolving flows of the gulf stream using a quasigeostrophic numerical model the potential for the growth of perturbations arising from errors and uncertainties in forecasts of the gulf stream is investigated by computing the singular vectors or so called optimal perturbations of time evolving flows using a linearized model and its adjoint the authors calculations reveal that the potential for rapid perturbation growth is greatest in regions of developing straining and shearing flows such regions include developing meanders and regions where eddies form and where existing eddies interact with the main gulf stream it is found that the optimal perturbations of the gulf stream share many features in common with those of the jet streams in the atmosphere the ideas and techniques developed in this paper have been applied to the problem of ensemble prediction of the gulf stream in part ii

constraining the enceladus plume using numerical simulation and cassini data abstract since its discovery the enceladus plume has been subjected to intense study due to the major effects that it has on the saturnian system and the window that it provides into the interior of enceladus however several questions remain and we attempt to answer some of them in this work in particular we aim to constrain the h2o production rate from the plume evaluate the relative importance of the jets and the distributed sources along the tiger stripes and make inferences about the source of the plume by accurately modeling the plume and constraining the model using the cassini inms and uvis data this is an extension of a previous work yeoh s k et al 2015 icarus 253 205 222 in which we only modeled the collisional part of the enceladus plume and studied its important physical processes in this work we propagate the plume farther into space where the flow has become free molecular and the cassini inms and uvis data were sampled then we fit this part of the plume to the inms h2o density distributions sampled along the e3 e5 and e7 trajectories and also compare some of the fit results with the uvis measurements of the plume optical depth collected during the solar occultation observation on 18 may 2010 we consider several vent conditions and source configurations for the plume by constraining our model using the inms and uvis data we estimate h2o production rates of several hundred kgs 1 400 500 kg s during the e3 and e7 flybys and 900 kg s during the e5 flyby these values agree with other estimates and are consistent with the observed temporal variability of the plume over the orbital period of enceladus hedman m m et al 2013 nature 500 182 184 in addition we determine that one of the tiger stripes cairo exhibits a local temporal variability consistent with the observed overall temporal variability of the plume we also find that the distributed sources along the tiger stripes are likely dominant while the jets provide a lesser contribution moreover our best fit solutions for the plume are sensitive to the vent conditions chosen the spreading angle of the jet produced is the main difference among the vent conditions and thus it appears to be an important parameter in fitting to these inms data sets in general we find that narrow jets produce better fits suggesting high mach numbers 5 at the vents this is supported by certain narrow features believed to be jets in both the inms and uvis data sets this tends to rule out sublimation from the surface but points to a deep underground source for the plume however the underground source can be either sublimation from an icy reservoir or evaporation from a liquid reservoir a high mach number at the vent also suggests subsurface channels with large variations in width and not fairly straight channels so that the gas can undergo sufficient expansion additionally the broad spreading angles inferred for the m sized grains ingersoll a p and ewald s p 2011 icarus 216 492 506 postberg f et al 2011 nature 474 620 622 cannot be due to spreading by the gas above the surface alone some other mechanism s must also be responsible perhaps occurring below the surface which further points to an underground source for the plume

field study of dispersion in a heterogeneous aquifer 1 overview and site description results are presented for a large scale natural gradient tracer experiment conducted in a heterogeneous alluvial aquifer at a site near columbus mississippi the study was initiated with a 48 hour pulse injection of 10 m3 of groundwater containing bromide and three organic tracers pentaflourobenzoic acid o trifluoromethylbenzoic acid and 2 6 diflourobenzoic acid over a 20 month period seven comprehensive samplings of the tracer plume were performed at approximately 1 to 4 month intervals using an extensive three dimensional sampling well network the dominant feature of the tracer plume that evolved during the study was the highly asymmetric concentration distribution in the longitudinal direction this asymmetry was produced by accelerating groundwater flow along the plume travel path that in turn resulted from an approximate 2 order of magnitude increase in the mean hydraulic conductivity between the near field and far field regions of the site the columbus study is distinct from previous natural gradient experiments because of the extreme heterogeneity of the aquifer the large scale spatial variations in groundwater velocity and the extensive set of hydraulic conductivity measurements for the aquifer

zonation for 3d aquifer characterization based on joint inversions of multimethod crosshole geophysical data predictive groundwater modeling requires accurate information about aquifer characteristics geophysical imaging is a powerful tool for delineating aquifer properties at an appropriate scale and resolution but it suffers from problems of ambiguity one way to overcome such limitations is to adopt a simultaneous multitechnique inversion strategy we have developed a methodology for aquifer characterization based on structural joint inversion of multiple geophysical data sets followed by clustering to form zones and subsequent inversion for zonal parameters joint inversions based on cross gradient structural constraints require less restrictive assumptions than say applying predefined petrophysical relationships and generally yield superior results this approach has for the first time been applied to three geophysical data types in three dimensions a classification scheme using maximum likelihood estimation is used to determine theparameters of a gaussian mixture model that defines zonal geometries

imaging and characterization of solute transport during two tracer tests in a shallow aquifer using electrical resistivity tomography and multilevel groundwater samplers 1 the relevance of aquifer heterogeneity for flow and transport is recognized broadly however its characterization is hampered by the inaccessibility of the subsurface time lapse electrical resistivity tomography ert offers the possibility of imaging noninvasively subsurface transport we present results of two tracer tests that were carried out successively in a shallow aquifer at the krauthausen test site germany the breakthroughs of an electrically conductive and a resistive tracer were monitored with ert and local multilevel groundwater samplers mls along two cross sections perpendicular to the mean flow direction sinking of the conductive salt tracer due to density effects was observed with ert we applied a stream tube model to characterize the spatially variable transport ert derived stream tube parameters showed similar patterns for the two tracer experiments reflecting the effect of aquifer heterogeneity on transport mls data did not show similar spatial patterns which indicates that these measurements may be prone to subtle changes of the flow field in the small sampling volume and mixing within screened wells between 50 and 10 of the tracer was recovered in the ert derived breakthrough curves compared with transport simulations in a homogeneous aquifer ert derived time integrated changes in electrical conductivity were locally larger but focused in a smaller area mls data indicated that in this area ert did not underestimate the tracer recovery the relatively low tracer recovery was attributed to undetected tracer breakthrough in regions with low ert sensitivity and in regions where the length of the tracer plume and the electrical conductivity contrast were small

spatial variations in the dust to gas ratio of enceladus plume abstract on day 138 of 2010 the plume of dust and gas emerging from enceladus south polar terrain passed between the sun and the cassini spacecraft this solar occultation enabled cassini s ultraviolet imaging spectrograph uvis and the visual and infrared mapping spectrometer vims to obtain simultaneous measurements of the plume s gas and dust components along the same lines of sight the uvis measurements of the plume s gas content are described in hansen et al 2011 grl 38 11202 while this paper describes the vims data and the information they provide about the plume s particle content together the vims and uvis measurements reveal that the plume material above baghdad and damascus sulci has a dust to gas mass ratio that is roughly an order of magnitude higher than the material above alexandria and cairo sulci similar trends in the plume s dust to gas ratio are also found in data obtained when cassini flew through the plume in 2009 during which time the ion and neutral mass spectrometer inms radio and plasma wave science instrument rpws and cosmic dust analyzer cda instruments made in situ measurements of the plume s gas and dust densities dong et al 2015 jgr 120 915 937 these and other previously published systematic differences in the material erupting from different fissures likely reflect variations in subsurface conditions across encealdus south polar terrain

three dimensional high resolution fluvio glacial aquifer analog part 1 field study summary describing the complex structures that exist in many sedimentary aquifers is crucial for reliable groundwater flow and transport simulation however hardly any aquifer can be inspected in such detail that all decimeter to meter heterogeneity is resolved aquifer analogs serve as surrogates to construct models of equivalent heterogeneity and thus imitate those features relevant for flow or transport processes gravel pits found in excavation show excellent sections of the sedimentary sequence and thus offer direct insight into the structural and textural composition of the subsoil this paper describes an approach to also inspect the third dimension by mapping during the ongoing excavation it is possible to obtain a three dimensional representation of the subsurface within a short period of time a detailed description of a case study is presented and the findings from sedimentological hydrogeological and geophysical analyses are compared the gravel pit is located near the town of herten in southwest germany where relatively young unconsolidated fluvio glacial and fluvial sediments in the rhine basin are mined the excavated gravel body is built up by architectural elements typical for braided river deposits the study generated a high resolution data set of lithofacies hydrofacies and ground penetrating radar gpr profiles it represents the basis for a full three dimensional geostatistical reconstruction presented in the second part comunian et al 2011

large scale natural gradient tracer test in sand and gravel cape cod massachusetts 1 experimental design and observed tracer movement a large scale natural gradient tracer experiment was conducted on cape cod massachusetts to examine the transport and dispersion of solutes in a sand and gravel aquifer the nonreactive tracer bromide and the reactive tracers lithium and molybdate were injected as a pulse in july 1985 and monitored in three dimensions as they moved as far as 280 m down gradient through an array of multilevel samplers the bromide cloud moved horizontally at a rate of 0 42 m per day it also moved downward about 4 m because of density induced sinking early in the test and accretion of areal recharge from precipitation after 200 m of transport the bromide cloud had spread more than 80 m in the direction of flow but was only 14 m wide and 4 6 m thick the lithium and molybdate clouds followed the same path as the bromide cloud but their rates of movement were retarded about 50 relative to bromide movement because of sorption onto the sediments

effects of stratification and bottom topography on the kuroshio path variation south of japan part i dependence of the path selection on velocity abstract numerical experiments are executed using a two layer inflow outflow ocean model with simplified geometry to investigate the effects of stratification and bottom topography on the path variation of the kuroshio south of japan in a flat bottom ocean the dependence of the kuroshio path selection on its inflow velocity vmax is basically the same as in a barotropic ocean that is the kuroshio takes a straight path at low vmax regime i a meandering path at high vmax regime ii and both paths at intermediate vmax regime iii multiple equilibrium state however the range of regime iii shifts to higher vmax by 0 10 0 30 m s 1 stratification causes and maintains the offshore shift of the current path south of kyushu through the conservation of potential vorticity as a result a small meander stagnates southeast of kyushu not developing into a large meander even for higher vmax since the vorticity supply from the coast is reduced for the same reason higher vmax is needed to maintain a meande