high resolution characterization of vadose zone dynamics using cross borehole radar characterization of the dynamics of moisture migration in the unsaturated zone of aquifers is essential if reliable estimates of the transport of pollutants threatening such aquifers are to be made electrical geophysical investigation techniques such as ground penetrating radar offer suitable methods for monitoring moisture content changes in the vadose zone moreover these tools permit relatively large measurement scales appropriate for hydrological models of unsaturated processes and thus they offer a distinct advantage over conventional measurement approaches ground penetrating radar when applied in transmission mode between boreholes can provide high resolution information on lithological and hydrological features the technique may be applied in tomographic mode and in a much simpler vertical profile mode both modes of measurement have been utilized using two boreholes 5 m apart located at a field site in the uk sherwood sandstone aquifer radar transmission measurements have been used to characterize the change in moisture content in unsaturated sandstone due to controlled water tracer injection continual monitoring of cross borehole radar measurements over an 18 month period has also permitted determination of travel times of natural loading to the system and has revealed the impact of subtle contrasts in lithology on changes in moisture content over time the time series of inferred moisture contents show clearly wetting and drying fronts migrating at a rate of approximately 2 m month 1 throughout the sandstone

assessing the likely value of gravity and drawdown measurements to constrain estimates of hydraulic conductivity and specific yield during unconfined aquifer testing 1 pumping of an unconfined aquifer can cause local desaturation detectable with high resolution gravimetry a previous study showed that signal to noise ratios could be predicted for gravity measurements based on a hydrologic model we show that although changes should be detectable with gravimeters estimations of hydraulic conductivity and specific yield based on gravity data alone are likely to be unacceptably inaccurate and imprecise in contrast a transect of low quality drawdown data alone resulted in accurate estimates of hydraulic conductivity and inaccurate and imprecise estimates of specific yield combined use of drawdown and gravity data or use of high quality drawdown data alone resulted in unbiased and precise estimates of both parameters this study is an example of the value of a staged assessment regarding the likely significance of a new measurement method or monitoring scenario before collecting field data

allochthonous oceanic basalts within the mesozoic accretionary complex of alexander island antarctica remnants of proto pacific oceanic crust the mesozoic lemay group accretionary complex of alexander island antarctica contains thrust bound slices of accreted ocean floor ocean islands and seamounts they represent fragments of proto pacific oceanic crust of which only a tiny remnant the phoenix plate remains off northern antarctic peninsula they therefore provide an excellent opportunity to sample the ancient oceanic crust that formerly occupied the southern pacific ocean all the basalts experienced sea floor and subduction accretion metamorphism ranging from zeolite to transitional blueschist facies on the basis of rare arth and other immobile trace element characteristics the basalts are divided into depleted morb n morb e morb and tholeiitic and alkaline oib oceanic basalts occur within two rock associations on alexander island basalt volcaniclastite chert and basalt volcaniclastite tuff the basalt volcaniclastite chert rock association is dominated by pillow lavas which have light ree depleted n morb geochemical characteristics and is interpreted as representing ocean floor formed at spreading centres locally sills of tholeiitic oib intrude the sequence the basalt volcaniclastite tuff rock association exposed in the lully foothills was formed in shallow water during the early jurassic it is geochemically varied consisting of basalts with n morb e morb and tholeiitic oib characteristics the association is interpreted to have been formed on a large seamount or ocean island

estimating lithologic and transport properties in three dimensions using seismic and tracer data the kesterson aquifer the identification of aquifer heterogeneities particularly flow paths and barriers has become a critical research topic in hydrology cross well seismic tomography may provide the needed resolution when used in conjunction with hydraulic head and tracer concentration measurements we demonstrate a field application and sensitivity analysis of the split inversion method sim which combines seismic hydraulic and tracer data to estimate the three dimensional zonation of aquifer properties along with the hydraulic properties for these zones for the kesterson aquifer in the san joaquin valley california we first invert seismic travel times measured between six well pairs to obtain seismic slowness 1 seismic velocity cross sections or tomograms we then use conditional simulation to provide three dimensional seismic slowness realizations next the sim is used to split several realizations into three lithologic zones and assign hydraulic properties to the zones to best match six tracer concentration histories

inversion of tracer test data using tomographic constraints 1 we have developed a methodology for inverting tracer test data using zonation information obtained from two dimensional radar tomograms to improve the typically overly smooth hydraulic conductivity fields obtained from conventional inversion of tracer test data the method simultaneously yields two dimensional estimates of hydraulic conductivity as well as petrophysical relationships that relate hydraulic conductivity to radar velocity these relationships can be assumed to be stationary throughout the area of investigation or to vary as a function of zonation using a synthetic three dimensional hydraulic conductivity field we apply the developed inversion methodology and explore the impact of the strength and stationarity of the petrophysical relationship as well as the impact of errors that are often associated with radar data acquisition such as unknown borehole deviation we find that adding radar tomographic data to tracer test data improves hydrogeological site characterization even in the presence of minor radar data errors the results are contingent on the assumption that a relationship between radar velocity and hydraulic conductivity exists therefore the applicability of the proposed method may be limited to field sites where this condition is partially or fully satisfied

geochemical characterization using geophysical data and markov chain monte carlo methods a case study at the south oyster bacterial transport site in virginia 1 the study demonstrates the use of ground penetrating radar gpr tomographic data for estimating sediment geochemical parameters using data collected at the department of energy south oyster bacterial transport site in virginia by exploiting the site specific mutual dependence of gpr attenuation and extractable fe ii and fe iii concentrations on lithofacies we develop a statistical model in which lithofacies and fe ii and fe iii concentrations at each pixel between the boreholes are considered as random variables the unknown variables are estimated by conditioning to the colocated gpr data and the lithofacies measurements along boreholes using a markov chain monte carlo method cross validation results show that the geophysical data constrained by lithofacies have the potential for providing high resolution multidimensional information on extractable fe ii and fe iii concentrations at the south oyster site

development of a joint hydrogeophysical inversion approach and application to a contaminated fractured aquifer this paper presents a joint inversion approach for combining crosshole seismic travel time and borehole flowmeter test data to estimate hydrogeological zonation the approach is applied to a complex fractured department of energy field site located at the oak ridge national laboratory in tennessee united states we consider seismic slowness the inverse of seismic velocity and hydrogeological zonation indicators as unknown variables and use a physically based model with unknown parameters to relate the seismic slowness to the zonation indicators we jointly estimate all the unknown parameters in the model by conditioning them to the crosshole seismic travel times as well as the borehole flowmeter data using a bayesian model and a markov chain monte carlo sampling method the fracture zonation estimates are qualitatively compared to bromide tracer breakthrough data and to uranium biostimulation experiment results the comparison suggests that the joint inversion approach adequately estimated the fractured zonation and that the fracture zonation influenced biostimulation efficacy our study suggests that the new joint hydrogeophysical inversion approach is flexible and effective for integrating various types of data sets within complex subsurface environments and that seismic travel time data have the potential to provide valuable information about fracture zonation

using time lapse gravity for groundwater model calibration an application to alluvial aquifer storage 1 the estimation of hydrological model parameters by calibration to field data is a critical step in the modeling process however calibration often fails because of parameter correlation here it is shown that time lapse gravity data can be combined with hydraulic head data in a coupled hydrogeophysical inversion to decrease parameter correlation in groundwater models this is demonstrated for a model of riverbank infiltration where combined inversion successfully constrains hydraulic conductivity and specific yield in both an analytical and a numerical groundwater model a sensitivity study shows that time lapse gravity data are especially useful to constrain specific yield furthermore we demonstrate that evapotranspiration and riverbed conductance are better constrained by coupled inversion to gravity and head data than to head data alone when estimating the four parameters simultaneously the six correlation coefficients were reduced from unity when only head data were employed to significantly lower values when gravity and head data were combined our analysis reveals that the estimated parameter values are not very sensitive to the choice of weighting between head and gravity data over a large interval of relative weights

estimating specific yield and storage change in an unconfined aquifer using temporal gravity surveys 1 two high precision gravity surveys were conducted to determine groundwater mass changes at a managed groundwater recharge site in northeastern colorado gravity data were collected during pumping and two months after pumping ceased during pumping gravity was lower by as much as 46 gal near the pumping wells and higher by as much as 90 gal near the recharge ponds in comparison to data collected after pumping had ceased these differences are attributed to changes in groundwater mass associated with drawdown and infiltration inverse modeling of the gravity data indicates a 5 1 105 m3 decrease in storage beneath the recharge ponds between the two surveys which we attribute to dissipation of the groundwater mound created by recharge during pumping this estimate of the change in groundwater storage is made independently of assumptions of physical properties of the aquifer dividing the change in water volume per unit area determined from the gravity modeling by the change in water level measured in wells provides an estimate of specific yield sy of 0 21 0 03 which is within the range of specific yield estimates derived from aquifer tests at the site water level changes predicted from the gravity data agree on average to within 0 45 m of those measured which we take to be an estimate of the uncertainty in water table depth predictions that can be obtained from gravimetric data in unconfined aquifers the study covers a 3 2 km2 area providing a prototype for similar studies at larger scales

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

characterization of seasonal local recharge using electrical resistivity tomography and magnetic resonance sounding a groundwater recharge process of heterogeneous hard rock aquifer in the moole hole experimental watershed south india is being studied to understand the groundwater flow behaviour significant seasonal variations in groundwater level are observed in boreholes located at the outlet area indicating that the recharge process is probably taking place below intermittent streams in order to localize groundwater recharge zones and to optimize implementation of boreholes a geophysical survey was carried out during and after the 2004 monsoon across the outlet zone magnetic resonance soundings mrs have been performed to characterize the aquifer and measure groundwater level depletion the results of mrs are consistent with the observation in boreholes but it suffers from degraded lateral resolution a better resolution of the regolith bedrock interface is achieved using electrical resistivity tomography ert ert results are confirmed by resistivity logging in the boreholes ert surveys have been carried out twice before and during the monsoon across the stream area the major feature of recharge is revealed below the stream with a decrease by 80 of the calculated resistivity the time lapse ert also shows unexpected variations at a depth of 20 m below the slopes that could have been interpreted as a consequence of a deep seasonal water flow however in this area time lapse ert does not match with borehole data numerical modelling shows that in the presence of a shallow water infiltration an inversion artefact may take place thus limiting the reliability of time lapse ert a combination of ert with mrs provides valuable information on structure and aquifer properties respectively giving a clue for a conceptual model of the recharge process infiltration takes place in the conductive fractured fissured part of the bedrock underlying the stream and clayey material present on both sides slows down its lateral dissipation

gravity changes and natural gas extraction in groningen gravity observations made over the groningen gasfield from 1978 onwards are available the existing gravity data were reanalysed and a new survey was carried out the observed gravity changes obtained during four surveys spanning an 18 year period were compared with the gravity effect due to natural gas extraction computed from the reservoir model and the production data the random error in the gravity values is small enough to detect the effect of gas extraction after a few years up to 2 gal year the trends obtained from observed and calculated gravity changes agree well within their expected error margins after statistical data snooping due to the inadequate measurement set up of the previous surveys systematic errors present in the gravity data hampered the use of this data for refinement of the reservoir and the production models however with improved gravity monitoring in particular a very systematic network set up and well calibrated instruments this should now be feasible by using the network analysis from the 1996 measurements for the planning of a network in space and time most of the current problems can be avoided

flow to a well of finite diameter in a homogeneous anisotropic water table aquifer a laplace transform solution is presented for the problem of flow to a partially penetrating well of finite diameter in a slightly compressible water table aquifer the solution which allows for evaluation of both pumped well and observation piezometer data accounts for effects of well bore storage and skin and allows for the noninstantaneous release of water from the unsaturated zone for instantaneous release of water from the unsaturated zone the solution approaches the line source solution derived by neuman as the diameter of the pumped well approaches zero delayed piezometer response which is significant during times of rapidly changing hydraulic head is included in the theoretical treatment and shown to be an important factor in accurate evaluation of specific storage by means of a hypothetical field example it is demonstrated that evaluations of specific storage ss using classical line source solutions may yield values of ss that are overestimated by a factor of 100 or more depending upon the location of the observation piezometers and whether effects of delayed piezometer response are included in the analysis theoretical responses obtained with the proposed model are used to suggest methods for evaluating specific storage

potential of electrical resistivity tomography to infer aquifer transport characteristics from tracer studies a synthetic case study 1 with time lapse electrical resistivity tomography ert transport processes in the subsurface can be imaged and monitored the information content of obtained spatiotemporal data sets opens new ways to characterize subsurface spatial variability difficulties regarding a quantitative interpretation of the imaged transport may arise from the fact that data inversion used in ert is generally underdetermined and that ert data acquisition is often limited to two dimensional 2 d image planes to address this problem we conducted a numerical tracer experiment in a synthetic heterogeneous aquifer with preset variability and spatial correlation of the hydraulic conductivity and monitored the tracer breakthrough in a 2 d image plane perpendicular to the mean flow direction using time lapse ert the tracer breakthrough patterns in the image plane were interpreted using equivalent transport models an equivalent convection dispersion equation to characterize the spatially averaged breakthrough and a stream tube model to characterize local breakthrough curves equivalent parameters derived from simulated and from ert inverted concentrations showed a good agreement which demonstrates the potential of ert to characterize subsurface transport using first order approximate solutions of stochastic flow and transport equations equivalent model parameters and their spatial variability were interpreted in terms of the local scale dispersion and the spatial variability of the hydraulic conductivity the spatial correlations of the stream tube velocity and of the hydraulic conductivity were found to be closely related consequently the hydraulic conductivity spatial correlation may be inferred from stream tube velocity distributions which can be observed with sufficiently high spatial resolution using ert

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

improved extraction of hydrologic information from geophysical data through coupled hydrogeophysical inversion 1 there is increasing interest in the use of multiple measurement types including indirect geophysical methods to constrain hydrologic interpretations to date most examples integrating geophysical measurements in hydrology have followed a three step uncoupled inverse approach this approach begins with independent geophysical inversion to infer the spatial and or temporal distribution of a geophysical property e g electrical conductivity the geophysical property is then converted to a hydrologic property e g water content through a petrophysical relation the inferred hydrologic property is then used either independently or together with direct hydrologic observations to constrain a hydrologic inversion we present an alternative approach coupled inversion which relies on direct coupling of hydrologic models and geophysical models during inversion we compare the abilities of coupled and uncoupled inversion using a synthetic example where surface based electrical conductivity surveys are used to monitor one dimensional infiltration and redistribution through this illustrative example we show that the coupled approach can provide significant reductions in uncertainty for hydrologic properties and associated predictions if the underlying model is a faithful representation of the hydrologic processes however if the hydrologic model exhibits structural errors the coupled inversion may not improve the hydrologic interpretation despite this limitation our results support the use of coupled hydrogeophysical inversion both for the direct benefits of reduced errors during inversion and because of the secondary benefits that accrue because of the extensive communication and sharing of data necessary to produce a coupled model which will likely lead to more thoughtful use of geophysical data in hydrologic studies

coupled hydrogeophysical inversion using time lapse magnetic resonance sounding and time lapse gravity data for hydraulic aquifer testing will it work in practice 1 temporal changes in water content can be directly related to the time lapse signals retrieved using magnetic resonance sounding tl mrs and relative gravimetry tl rg previous studies suggest that tl rg measurements can potentially provide accurate estimates of aquifer characteristics in an aquifer pumping test experiment when used in a coupled hydrogeophysical inversion approach however these studies considered highly idealized conditions the aim of this paper is twofold first we investigate three major issues which likely limit the practical utility of tl rg for pumping test monitoring partially penetrating pumping wells in anisotropic aquifers delayed drainage effects and typical data errors for tl rg second we introduce tl mrs in a similar coupled hydrogeophysical inversion framework and compare the performance of tl mrs and tl rg for pumping test monitoring for this purpose we consider a virtual pumping test for which we generate synthetic drawdown tl mrs and tl rg observations and subsequently determine the aquifer parameters in an inverse parameter estimation approach the inclusion of tl rg and tl mrs data did slightly improve parameter estimates for the specific yield and hydraulic conductivity when considering a fully penetrating well and minimal data error using more conservative tl rg and tl mrs data error estimates according our own field experience strongly limited the informative value of the tl rg data tl mrs data was less affected by this for a partially penetrating well under anisotropic conditions parameter uncertainty could be reduced more effectively compared to a fully penetrating well delayed drainage effects did not limit the ability of the tl mrs and tl rg data to reduce parameter uncertainty significantly the incorporation of representative measurement error correlation in the tl rg data did not affect its informative value a local sensitivity analysis showed that observations were most sensitive to the pumping rate and the thickness specific yield and hydraulic conductivity of the aquifer the inclusion of tl mrs data proved to be more effective to constrain the aquifer parameters compared with tl rg the inclusion of both tl rg and tl mrs had limited added value compared to tl mrs only we conclude that this particular application of coupled hydrogeophysical inversion has limited potential for tl rg while tl mrs appears to be a more promising method

closed loop gpr data inversion for soil hydraulic and electric property determination we propose an integrated electromagnetic hydrodynamic inverse modeling approach for identifying field scale unsaturated soil hydraulic properties and electric profiles from off ground time lapse ground penetrating radar data hydrodynamic modeling based on the one dimensional richards equation with homogeneous soil hydraulic parameters is used to physically constrain the full wave radar electromagnetic inverse problem in a closed loop significant effects can be observed of water dynamics on the time lapse radar data and numerical studies demonstrate the uniqueness of the inverse solution the results suggest that the method is promising for non invasive characterization of the shallow subsurface and monitoring of its dynamics

observations of the variation in aerosol and cloud microphysics along the 20 s transect on 13 november 2008 during vocals rex abstractobservations are presented of the structure of the marine boundary layer mbl in the southeastern pacific made with the u k bae 146 aircraft on 13 november 2008 as it flew at a variety of altitudes along 20 s between the coast of chile and a buoy 950 km offshore during the variability of american monsoon systems vamos ocean cloud atmosphere land study vocals regional experiment rex the purpose of the study is to determine the variations along the 20 s transect in the clouds and boundary layer on this particular day as compared to the typical structure determined from the composite studies the aircraft flew in three regions on this day relatively continuous thick stratocumulus clouds open cells and closed cells results show three particular features first the results of the cloud microphysics are consistent with the typical behavior showing a decrease in aerosol particles by a factor of 3 4 and a decrease in cloud droplet number concentration westward from the coast from about 200

fully coupled hydrogeophysical inversion of synthetic salt tracer experiments 1 we present a method for the determination of hydraulic conductivity from monitoring of salt tracer tests by electrical resistivity tomography ert to ensure that the underlying principles of flow transport and geoelectrics are obeyed in the inversion we perform a fully coupled hydrogeophysical analysis using temporal moments of electrical potential perturbations in the predictive mode we use moment generating equations with corresponding adjoint equations for the evaluation of sensitivities for inversion we apply the quasi linear geostatistical inversion approach the method is tested in a synthetic case study mimicking a laboratory scale quasi two dimensional sandbox in which 48 electrodes and 8 piezometers are used the hydraulic conductivity field is estimated from the mean arrival times of electrical potential perturbations and hydraulic heads the estimated hydraulic conductivity field reproduces most features with however a loss of variability even though only the temporal moments of the electrical signals are used for inversion the transient behavior is satisfactorily recovered also the spatial patterns of concentration arrival times in the true and estimated cases are in good agreement so that the propagation of the tracer plume can be followed fairly accurately we test the effects of large measurement errors and erroneous prior information on the performance of the inversion while prior statistical parameters are of minor importance in detecting the major pattern of hydraulic conductivity a large measurement error could have an important impact on the solution also the choice of electrode configurations appears to be important in particular strictly surface based geoelectrical surveys do not seem to be very suitable for identifying spatial patterns of hydraulic conductivity by ert monitoring of salt tracer tests within aquifers

the utility of gravity and water level monitoring at alluvial aquifer wells in southern arizona coincident monitoring of gravity and water levels at 39 wells in southern arizona indicate that water level change might not be a reliable indicator of aquifer storage change for alluvial aquifer systems one reason is that water levels in wells that are screened across single or multiple aquifers might not represent the hydraulic head and storage change in a local unconfined aquifer gravity estimates of aquifer storage change can be approximated as a one dimensional feature except near some withdrawal wells and recharge sources the aquifer storage coefficient is estimated by the linear regression slope of storage change estimated using gravity methods and water level change nonaquifer storage change that does not percolate to the aquifer can be significant greater than 3 gal when water is held in the root zone during brief periods following extreme rates of precipitation monitor ing of storage change using gravity methods at wells also can improve understanding of local hydrogeologic conditions

simulated gravitational response to hydraulic testing of unconfined aquifers abstract the gravitational response to hydraulic testing of shallow unconfined aquifers 8 m s 2 at the pumping well the response at the 1 gal level can extend hundreds of meters away from the pumping well at a distance of 1 m survey resolutions between 0 002 to 0 15 and 0 03 to 2 gal are required to delineate incremental drawdown at the 0 02 and 0 3 m levels respectively below the point of measurement

estimation of field scale soil hydraulic and dielectric parameters through joint inversion of gpr and hydrological data 1 a method is described for the joint use of time lapse ground penetrating radar gpr travel times and hydrological data to estimate field scale soil hydraulic parameters we build upon previous work to take advantage of a wide range of cross borehole gpr data acquisition configurations and to accommodate uncertainty in the petrophysical function which relates soil porosity and water saturation to the effective dielectric constant we first test the inversion methodology using synthetic examples of water injection in the vadose zone realistic errors in the petrophysical function result in substantial errors in soil hydraulic parameter estimates but such errors are minimized through simultaneous estimation of petrophysical parameters in some cases the use of a simplified gpr simulator causes systematic errors in calculated travel times simultaneous estimation of a single correction parameter sufficiently reduces the impact of these errors we also apply the method to the u s department of energy doe hanford site in washington where time lapse gpr and neutron probe np data sets were collected during an infiltration experiment we find that inclusion of gpr data in the inversion procedure allows for improved predictions of water content compared to predictions made using np data alone these examples demonstrate that the complimentary information contained in geophysical and hydrological data can be successfully extracted in a joint inversion approach moreover since the generation of tomograms is not required the amount of gpr data required for analyses is relatively low and difficulties inherent to tomography methods are alleviated finally the approach provides a means to capture the properties and system state of heterogeneous soil both of which are crucial for assessing and predicting subsurface flow and contaminant transport

transient flow of water to a well in an unconfined aquifer applicability of some conceptual models currently available methods for interpreting data from unconfined aquifers are based on analytical solutions which restrict attention to flow in the saturated zone and account for drainage of water from the unsaturated zone through a source term the parameter specific yield sy is assumed to dictate the total quantity of water that is derivable through the desaturation process it is commonly assumed that flow in the unsaturated zone has little effect on flow in the saturated zone and therefore that all the drainable water is instantly delivered at the water table as it declines in response to pumping in a model proposed in 1954 boulton empirically assumed that the drainable water associated with sy is released gradually at the water table as an exponential function of time this concept of boulton is similar to the notion of first order kinetics frequently used to handle chemical transformations boulton s model is considered by some to have no physical basis numerical experiments performed on sand columns with reasonable properties suggest that vertical drainage of water at the water table due to a falling water table is a time dependent process which is mathematically more complex than a simple exponential relation although boulton did not provide a rational physical explanation his exponential assumption has some merit in that it implicitly provides for a time dependent drainage process which seems to occur in the unsaturated zone however the simple exponential approximation is not adequate to account for what is seemingly a complex process it appears that a physically comprehensive model of radial flow in an unconfined aquifer will combine time dependent drainage from above the water table with vertical components of flow in the saturated zone an additional assumption frequently made is that the well can be treated as a line source results from numerical experiments suggest that caution is in order before neglecting effects of well bore storage in interpreting data from tests on unconfined aquifers

a geostatistical framework for incorporating seismic tomography auxiliary data into hydraulic conductivity estimation abstract a geostatistical approach is presented for the inclusion of seismic tomography data and sonic log data into the estimation of hydraulic conductivity the procedure accounts for the errors in seismic tomography inversion and for the correlation of such errors the proposed methodology consists of two steps 1 the cross variogram inference is carried out using only the data at the wellbore both hydraulic and seismic 2 a co kriging procedure takes the cross well data into account to interpolate between boreholes no postulated a priori relationship is needed in order to illustrate the methodology a synthetic data set is generated on the basis of evidence from published case studies and simplified physical considerations the numerical experiments show that the choice of the excitation frequency is critical a trade off exists between the need for a high resolution survey asking for higher frequencies and the need for a good correlation between hydraulic conductivity and seismic properties asking for frequencies below the squirt frequency of the medium in the simulation using seismic data with the best excitation frequency 1 khz in this case the mean squared error of the hydraulic conductivity estimate is two thirds lower than using hydraulic data alone it is important to note also that only a part of the interwell region is adequately sampled by the tomographic experiment such a region can be readily identified by calculating the energy of the quasi null space through singular value decomposition of the tomographic matrix in planning this type of experiments it is necessary to carefully verify case by case whether the adopted range of high frequencies does not prevent the seismic energy from propagating effectively from sources to receivers

spatial correlation structure estimation using geophysical and hydrogeological data the large spatial variability of hydraulic properties in natural geologic systems over a wide range of scales and the difficulty of collecting representative and sufficient hydraulic property measurements using conventional sampling techniques render estimation of spatial correlation parameters difficult further compounding the estimation problem is the observation that the integral scale estimate is a function of the measurement support scale to mitigate these problems we investigate the use of tomographic geophysical data in combination with hydrogeological data in the spatial correlation estimation procedure two synthetic case studies were investigated where the scale of the geophysical measurements were varied relative to the scale of the hydrogeological properties the spatial correlation structure parameter estimation procedure was performed in the spectral domain where analysis of data having different support scales and spatial sampling windows was facilitated comparison of the spatial correlation structure parameters estimated from measured data with those of the synthetic aquifers revealed which type of data tomographic hydrogeological or a combination of both was most effective for recovering spatial correlation statistics under different sampling heterogeneity conditions these synthetic case studies suggest that collection of a few tomographic profiles and interpretation of these profiles together with limited well bore data can yield correlation structure information that is otherwise obtainable only from extensive hydrological sampling

ground penetrating radar for environmental applications abstract ground penetrating radar gpr is a near surface geophysical technique that can provide high resolution images of the dielectric properties of the top few tens of meters of the earth in applications in contaminant hydrology radar data can be used to detect the presence of liquid organic contaminants many of which have dielectric properties distinctly different from those of the other solid and fluid components in the subsurface the resolution approximately meter scale of the radar imaging method is such that it can also be used in the development of hydrogeologic models of the subsurface required to predict the fate and transport of contaminants gpr images are interpreted to obtain models of the large scale architecture of the subsurface and to assist in estimating hydrogeologic properties such as water content porosity and permeability its noninvasive capabilities make gpr an attractive alternative to the traditional methods used for subsurface characterization

hydrogeological interpretation and potential of the new magnetic resonance sounding mrs method abstract this study reviews the up to date hydrogeological contribution of the new geophysical magnetic resonance sounding mrs method and presents new interpretation ideas and potential regarding various hydrogeological applications the main advantage of the mrs method as compared to other geophysical methods is in its water selectivity mrs is commercially available but is also the subject of r d to minimize a number of limitations related not only to data acquisition but also to hydrogeological data interpretation the two main mrs output data types are free water content mrs and decay time constant t d relations between mrs and effective porosity specific yield and specific storage are discussed in the framework of an original groundwater storage concept t d is correlated empirically with hydraulic conductivity however such correlation is not yet quantified for various rock types so t d has to be calibrated by borehole data as an improvement of the data interpretation a proposal of a new multi decay approach is presented the advantage of such analysis is that it combines storage and flow property characteristics in assessing water content at various pore size fractions and the disadvantage is that it is applicable only at large signal to noise ratios five case examples are used to show that combined interpretation of mrs and t d can be used to evaluate subsurface hydrostratigraphy although such analysis is vulnerable to equivalence error and its resolution decreases with depth mrs with large volume averaging schema and current limitation to 1d approach is already suitable for groundwater modelling applications and for evaluation of groundwater potential in the mrs measurement scale 100 100 m 2 but is not yet optimized for well siting mrs can detect water in the unsaturated zone which can be potentially used in real time subsurface flux monitoring field experiments indicate that mrs is not appropriate for groundwater salinity detection no field experiments have yet been made to detect hydrogenated compounds like hydrocarbons and tracers in the subsurface