the impact of rapid coastline changes and sea level rise on the tides in the bohai sea china 1 the tidal regime in the bohai sea china is investigated using observations and an established numerical tidal model the area has recently experienced rapid coastline changes due to natural developments of the yellow river delta and large scale anthropogenic land reclamation these morphological changes are not reflected in most global bathymetric databases and are thus rarely incorporated into investigations of the bohai sea it is shown that there have indeed been significant changes in the tidal regime in the bohai sea over the last 35 years with m2 amplitudes changing up to 20 cm in some parts the model captures some of these changes when the appropriate bathymetries are used furthermore the simulations show that the tides in the bohai sea have become more sensitive to future sea level rise and the way in which it is implemented in the model i e whether or not flood defenses are included these sensitivity changes are due to the recent coastal developments

joint two dimensional dc resistivity and seismic travel time inversion with cross gradients constraints it is now common practice to perform collocated dc resistivity and seismic refraction surveys that complement each other in the search for more accurate characterization of the subsurface although conventional separate dc resistivity and seismic models can be diagnostic we posit that better results can be derived from jointly estimated models we make the assumption that both methods must be sensing the same underlying geology and have developed an innovative resistivity velocity cross gradients relationship to evaluate the structural features common to both methods the cross gradients function is incorporated as a constraint in a nonlinear least squares problem formulation which is solved using the lagrange multiplier method the resultant iterative two dimensional 2 d joint inversion scheme is successfully applied to synthetic data serving as validation tests here and to field data from collocated dc resistivity and seismic refraction profiling experiments and also compared to conventional separate inversion results the joint inversion results are shown to be superior to those from separate 2 d inversions of the respective data sets since our algorithm leads to resistivity and velocity models with remarkable structural agreement

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

joint two dimensional cross gradient imaging of magnetotelluric and seismic traveltime data for structural and lithological classification summary collocated magnetotelluric mt and seismic profiling is emerging as a necessary combined approach for deep and near surface imaging but the resulting experimental data are typically interpreted separately since no production programs exist for multidimensional joint inversion of mt and seismic data we present a joint 2 d inversion approach for imaging collocated mt and seismic refraction data with cross gradient structural constraints we describe the main features of the algorithm and first apply it to synthetic data generated for a hypothetical complex geological model for the synthetic data we find that the scheme leads to models with remarkable structural resemblance and improved estimates of electrical resistivity and seismic velocity we apply the scheme to near surface field data to test the consistency of a previously suggested resistivity velocity interrelationship and its potential use for subsurface lithofacies discrimination or structural classification the mt seismic relationship is found to be in excellent accord with that derived previously for dc resistivity and seismic data set at the test site our results suggest that joint mt seismic cross gradient imaging leads to improved characterization of heterogeneous geological targets at near surface to mantle depths

two dimensional joint inversion of radiomagnetotelluric and direct current resistivity data an algorithm for the two dimensional 2d joint inversion of radiomagnetotelluric and direct current resistivity data was developed this algorithm can be used for the 2d inversion of apparent resistivity data sets collected by multi electrode direct current resistivity systems for various classical electrode arrays wenner schlumberger dipole diplole pole dipole and radiomagnetotelluric measurements jointly we use a finite difference technique to solve the helmoltz and poisson equations for radiomagnetotelluric and direct current resistivity methods respectively a regularized inversion with a smoothness constrained stabilizer was employed to invert both data sets the radiomagnetotelluric method is not particularly sensitive when attempting to resolve near surface resistivity blocks because it uses a limited range of frequencies on the other hand the direct current resistivity method can resolve these near surface blocks with relatively greater accuracy initially individual and joint inversions of synthetic radiomagnetotelluric and direct current resistivity data were compared and we demonstrated that the joint inversion result based on this synthetic data simulates the real model more accurately than the inversion results of each individual method the developed 2d joint inversion algorithm was also applied on a field data set observed across an active fault located close to the city of kerpen in germany the location and depth of this fault were successfully determined by the 2d joint inversion of the radiomagnetotelluric and direct current resistivity data this inversion result from the field data further validated the synthetic data inversion results

joint inversion of tem and distorted mt soundings some effective practical considerations accurate layered earth interpretation of magnetotelluric mt apparent resistivity sounding curves distorted by the presence of near surface 3 d bodies in an otherwise horizontally stratified ground requires that the curves be shifted to the level they would have assumed in the absence of these anomalous small size bodies the most popular preinterpretation processing involves shifting the biased mt apparent resistivity curves to the levels determined by some additional data this paper examines the nature of tem field data their relationship with mt data and their usefulness in constraining the interpretation of mt data at locations affected by near surface 3 d effects the mt apparent resistivity curves are neglected in a joint inversion scheme involving the undistorted equivalent phase information and tem data thus eliminating the need for preinterpretation data processing or correction of statically shifted curves this approach is efficient and effective and since an overlapping tem observatio

breakthrough curve moments scaling in hyporheic exchange the interaction between stream flow and bed forms creates an uneven distribution of near bed energy heads which is the driving force of hyporheic exchange owing to the large disparity of advection characteristic times in the stream and within the hyporheic zone solute mass exchange is often modeled by considering the latter as an immobile region in a recent contribution gonzalez pinzon et al 2013 showed that existing models employing this hypothesis are structurally inconsistent with the scaling revealed by the analysis of 384 breakthrough curves collected in 44 streams across five continents motivated by this result we analyze the scaling characteristics of a model that we recently developed by combining the analytical solution of the advective flow within the hyporheic zone with a lagrangian solute transport model results show that similarly to the experimental data our model predicts breakthrough curves with a constant skewness irrespective of the stream size and that the scaling of the first three moments observed by gonzalez pinzon et al 2013 is also respected moreover we propose regression curves that relate the first three moments of the residence time distribution with the alternate bar dimensionless depth ybm a quantity that is easily measurable in the field the connection between btc moments and ybm opens new possibilities for modeling transport processes at the catchment scale

cooperative inversion of geophysical data geophysical inversion by iterative modeling involves fitting observations by adjusting model parameters both seismic and potential field model responses can be influenced by the adjustment of the parameters of the rock properties the objective of this cooperative in version is to obtain a model which is consistent with all available surface and borehole geophysical data al though inversion of geophysical data is generally non unique and ambiguous we can lessen the ambiguities by inverting all available surface and borehole data this paper illustrates this concept with a case history in which surface seismic data sonic logs surface gravity data and borehole gravity meter bhgm data are ad equately modeled by using least squares inversion and a series offorward modeling steps the traditional analysis of various geophysical data sets has been termed integrated interpretation such analysis has traditionally involved much processing modeling and subjec tive interpretation in order to develop a geologic model which is consistent with various surface and borehole geophysical data a method which automates some of the above pro cedures is least squares inversion this procedure perturbs an initial set of model parameters in order to fit the observed data least squares inversion is described in many papers in cluding those of jackson 1972 wiggins 1972 jupp and vozoff 1975 and lines and treitel 1984 this inversion technique could also be termed automated iterative mod eling in terms of modeling different geophysical data sets there are many possible approaches which allow inversion of a given data set and it is doubtful whether one single recipe will prove suitable for all problems nevertheless by jointly invert ing various types of geophysical observations we may lessen the extent of some of the ambiguities inherent in individual data sets lafehr 1984 gives a germane discussion of several reasons for this type of coordinated geophysical effort in the present study we define cooperative inversion as the esti mation of a subsurface model which is consistent with various independent geophysical data sets in the case discussed in this paper these data sets include surface and borehole observa tions of the seismic and gravity responses in our definition cooperative inversion may include either joint inversion or sequential inversion

boat towed radio magnetotelluric and controlled source audio magnetotelluric study to resolve fracture zones at aspo hard rock laboratory site sweden boat towed radio magnetotelluric rmt measurements using signals between 14 and 250 khz have attracted increasing attention in the near surface applications for shallow water and archipelago areas

delineating fracture zones using surface tunnel surface seismic data p s and s p mode conversions a surface tunnel surface seismic experiment was conducted at the aspo hard rock laboratoryto study the seismic response of major fracture systems intersecting the tunnel a newly developedthree com

planning of urban underground infrastructure using a broadband seismic landstreamer tomography results and uncertainty quantifications from a case study in southwestern sweden abstractwe have developed a multicomponent broadband seismic landstreamer system based on digital sensors and particularly suitable for noisy environments and areas in which high resolution images of the subsurface are desired we have evaluated results interpretations and approaches using the streamer in the planning of an approximately 3 km long underground tunnel in the city of varberg in the southwestern sweden prospective targets were imaging of the shallow 20 m bedrock surface and weak zones such as fracture and shear zones over the course of three weeks 25 profiles were acquired with a total length of approximately 7 5 km using a source and receiver spacing of 2 4 m a novel approach of the data acquisition was to integrate the landstreamer with wireless sensors in areas in which the accessibility was restricted by roads and also to increase the source receiver distances offsets although the area was highly noisy the seismic data in conjunction with available boreholes successfully l

2d joint inversion of rmt and ert data versus individual 3d inversion of full tensor rmt data an example from trecate site in italy tensor radiomagnetotelluric rmt and electrical resistivity tomography ert data were acquired along 10 parallel lines to image electrical resistivity of the vadose and the saturated zone in an a

semianalytical analysis of hyporheic flow induced by alternate bars 1 we investigate the effects of alternate bar morphology on the hyporheic flow in gravel bed rivers our goal is to investigate the relations between residence time distribution of a conservative tracer and the parameters controlling bed form morphology we assume homogeneous isotropic or anisotropic hydraulic properties of the streambed sediment and constant flow regime in equilibrium with the bed form which is considered fixed because its formation timescale is much longer than that of the subsurface flow under these assumptions we solve the in stream and hyporheic flow fields analytically in a three dimensional domain we approximate the former with the shallow water equations and model the latter as a darcian flow the two systems are linked through the hydraulic head distribution which is predicted at the streambed by the surface model and applied as a boundary condition to the hyporheic flow model we solve the solute transport equation in the hyporheic zone for a conservative tracer by means of particle tracking our model predicts that the mean value and variance of the hyporheic residence time depend on the alternate bar amplitude at equilibrium this result is found to be applicable also to discharges that are lower 70 in our simulations than the formative and submerge the bars entirely moreover our analysis shows that 95 of the hyporheic flow is confined in a near bed layer whose depth is about the width of the channel and shallows from low to steep gradient streams this causes the hyporheic mean residence time to reach a threshold when the alluvial depth is deeper than the channel width our results also show that as the stream slope increases the streamlines compact near to the streambed thereby reducing the mean residence time and its variance finally we observe that the hyporheic residence time of pulse injections of passive solutes is lognormally distributed with the mean value depending in a simple manner on the amplitude of the alternate bars

depth of investigation in electromagnetic sounding methods the time or frequency at which the electromagnetic em response of a buried inhomogeneity can first be measured is determined by its depth of burial and the average conductivity of the overlying section it is relatively independent of the type of source or receiver and their separation the ability to make measurements at this time or frequency however depends on the sensitivity and accuracy of the instrumentation the signal strength and the ambient noise level these factors affect different em sounding systems in surprisingly different ways for the magnetotelluric mt method it is possible to detect a buried half space under about 1 5 skin depths of overburden the maximum depth of investigation is virtually unbounded because of high signal strengths at low frequencies transient electromagnetic tem soundings on the other hand have a limited depth of penetration but are less affected by static shift errors for tem a buried inhomogeneity can be detected under about one diffusion depth of overburden for conventional near zone sounding in which induced voltage is measured impulse response the depth of investigation is proportional to the 1 5 power of the source moment and ground resistivity by contrast if the receiver is a magnetometer step response system the depth of investigation is proportional to the 1 3 power of source moment and is no longer a function of resistivity magnetic field measurements may therefore be superior for exploration in conductive areas such as sedimentary basins far zone or long offset tem soundings are traditionally used for deep exploration the depth of investigation for a voltage receiver is proportional to the 1 4 power of source moment and resistivity and is inversely proportional to the source receiver separation magnetic field measurements are difficult to make at long offsets because instrumental accuracy limits the measurement of the very slow decay of the magnetic field frequency domain controlled source systems are ideally suited for sounding at the very shallow depths needed for engineering archaeological and groundwater applications because of the relative ease of extending the measurements to arbitrarily high frequencies and also because geometric soundings can be made at low induction numbers

joint electromagnetic and seismic inversion using structural constraints we have developed a frequency domain joint electromagnetic em and seismic inversion algorithm for reservoir evaluation and exploration applications em and seismic data are jointly inverted using a cross gradient constraint that enforces structural similarity between the conductivity image and the compressional wave p wave velocity image the inversion algorithm is based on a gauss newton optimization approach because of the ill posed nature of the inverse problem regularization is used to constrain the solution the multiplicative regularization technique selects the regularization parameters automatically improving the robustness of the algorithm a multifrequency data weighting scheme prevents the high frequency data from dominating the inversion process when the joint inversion algorithm is applied in integrating marine controlled source electromagnetic data with surface seismic data for subsea reservoir exploration applications and in integrating crosswell em and sonic data for reservoir monitoring and evaluation applications results improve significantly over those obtained from separate em or seismic inversions

the effects of discharge and slope on hyporheic flow in step pool morphologies this paper focuses on surface subsurface water exchange in a steep coarse bedded stream with a step pool morphology we use both flume experiments and numerical modelling to investigate the influence of stream discharge channel slope and sediment hydraulic conductivity on hyporheic exchange the model step pool reach whose topography is scaled from a natural river consists of three step pool units with 0 1 m step heights discharges ranging between base and over bankfull flows scaled values of 0 3 4 5 l s and slopes of 4 and 8 results indicate that the deepest hyporheic flow occurs with the steeper slope and at moderate discharges and that downwelling fluxes at the base of steps are highest at the largest stream discharges in contrast to findings in a pool riffle morphology those in this study show that steep slopes cause deeper surface subsurface exchanges than gentle slopes numerical simulation results show that the portion of the hyporheic zone influenced by surface water temperature increases with sediment hydraulic conductivity these experiments and numerical simulations emphasize the importance of topography sediment permeability and roughness elements along the channel surface in governing the locations and magnitude of downwelling fluxes and hyporheic exchange our results show that hyporheic zones in these steep streams are thicker than previously expected by extending the results from streams with pool riffle bed forms copyright 2014 john wiley sons ltd

spatiotemporal variability of hyporheic exchange through a pool riffle pool sequence 1 stream water enters and exits the streambed sediment due to hyporheic fluxes which stem primarily from the interaction between surface water hydraulics and streambed morphology these fluxes sustain a rich ecotone whose habitat quality depends on their direction and magnitude the spatiotemporal variability of hyporheic fluxes is not well understood over several temporal scales and consequently we studied their spatial and temporal variation over a pool riffle pool sequence at multiple locations from winter to summer we instrumented a pool riffle pool sequence of bear valley creek an important salmonid spawning gravel bed stream in central idaho with temperature monitoring probes recording at high temporal resolution 12 minute intervals using the thermal time series weekly winter season seepage fluxes were calculated with a steady state analytical solution and spring summer fluxes with a new analytical solution that can also quantify the streambed thermal properties longitudinal pool riffle pool conceptualizations of downwelling and upwelling behavior were generally observed except during the winter season when seepage fluxes tended toward downwelling conditions seepage fluxes near the edges of the channel were typically greater than fluxes near the center of the channel and demonstrated greater seasonal variability results show that the interaction between streamflow and streambed topography has a primary control near the center of the channel whereas the interaction between stream water and groundwater table has a primary control on seepage fluxes near the banks of the stream

joint inversion of lake floor electrical resistivity tomography and boat towed radio magnetotelluric data illustrated on synthetic data and an application from the aspo hard rock laboratory site sweden joint inversion of lake floor electrical resistivity tomography and boat towed radio magnetotelluric data illustrated on synthetic data and an application from the aspo hard rock laboratory site sweden

joint inversions of three types of electromagnetic data explicitly constrained by seismic observations results from the central okavango delta botswana the okavango delta of northern botswana is one of the world s largest inland deltas or megafans to obtain information on the character of sediments and basement depths audio magnetotelluric amt

hyporheic exchange in gravel bed rivers with pool riffle morphology laboratory experiments and three dimensional modeling received 7 june 2005 revised 30 june 2006 accepted 25 august 2006 published 31 january 2007 1 we report the first laboratory simulations of hyporheic exchange in gravel pool riffle channels which are characterized by coarse sediment steep slopes and three dimensional bed forms that strongly influence surface flow these channels are particularly important habitat for salmonids many of which are currently at risk worldwide and which incubate their offspring within the hyporheic zone here we perform a set of laboratory experiments examining the effects of discharge and bed form amplitude on hyporheic exchange with surface subsurface mixing measured directly from the concentration decay of a conservative tracer fluorescein injected into the surface flow near bed pressure measurements were also used to predict hyporheic exchange from a three dimensional pumping transport model comparison of the predicted and observed hyporheic exchange shows good agreement indicating that the major mechanism for exchange is bed form induced advection however the effect of bed forms is modulated by discharge and the degree of topographic submergence we also tested the performance of the hydrostatic pressure as a proxy for the observed near bed pressure in driving hyporheic exchange which would facilitate field measurement and analysis of hyporheic flow in natural rivers we found agreement with measured hyporheic exchange only for low bed form amplitudes and high flows

joint inversion of p wave velocity and density application to la soufriere of guadeloupe hydrothermal system we present the result of a 3 d gravity and p wave traveltime joint inversion applied to the hydrothermal system of la soufri ere of guadeloupe the joint inversion process is used here to overcome the different resolution limitations attached to the two data sets p wave traveltimes were obtained from three active seismic surveys that were conducted from 2001 to 2007 gravity data collected during a microgravity campaign is described in a companion paper we use a joint inversion process based on a bayesian formulation and a deterministic iterative approach the coupling between slowness and density is introduced through a supplementary constraint in the misfit function that tries to minimize the distance between parameter values and a theoretical relationship this relationship is derived from measurements on samples representative of mt pel ee of martinique and la soufri ere volcanoes we chose a grid discretization that leads to an under determined problem that we regularize using spatial exponential covariance between the nodes parameters our results are compared to geophysical electromagnetic results obtained using resistivity and vlf surveys they confirm the presence of highly contrasted dense fast and light slow zones in la soufri ere dome and crater basement our images suggest however that some non conductive zones may be massive andesite bodies rather than argilized zones and that these bodies may have deeper roots than hypothesized

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

retracted and replaced a modelling study of hyporheic exchange pattern and the sequence size and spacing of stream bedforms in mountain stream networks oregon usa this article has been retracted and replaced see retraction and replacement notice doi 10 1002 hyp 6350 studies of hyporheic exchange flows have identified physical features of channels that control exchange flow at the channel unit scale namely slope breaks in the longitudinal profile of streams that generate subsurface head distributions we recently completed a field study that suggested channel unit spacing in stream longitudinal profiles can be used to predict the spacing between zones of upwelling flux of hyporheic water into the stream and downwelling flux of stream water into the hyporheic zone in the beds of mountain streams here we use two dimensional groundwater flow and particle tracking models to simulate vertical and longitudinal hyporheic exchange along the longitudinal axis of stream flow in second third and fourth order mountain stream reaches modelling allowed us to 1 represent visually the effect that the shape of the longitudinal profile has on the flow net beneath streambeds 2 isolate channel unit sequence and spacing as individual factors controlling the depth that stream water penetrates the hyporheic zone and the length of upwelling and downwelling zones 3 evaluate the degree to which the effects of regular patterns in bedform size and sequence are masked by irregularities in real streams we simulated hyporheic exchange in two sets of idealized stream reaches and one set of observed stream reaches idealized profiles were constructed using regression equations relating channel form to basin area the size and length of channel units step size pool length etc increased with increasing stream order simulations of hyporheic exchange flows in these reaches suggested that upwelling lengths increased from 2 7 m to 7 6 m and downwelling lengths increased from 2 9 m to 6 0 m with increase in stream order from second to fourth order step spacing in the idealized reaches increased from 5 3 m to 13 7 m as stream size increased from second to fourth order simulated upwelling lengths increased from 4 3 m in second order streams to 9 7 m in fourth order streams with a pool riffle step channel unit sequence and increased from 2 5 m to 6 1 m from second to fourth order streams with a pool step riffle channel unit sequence downwelling lengths also increased with stream order in these idealized channels our results suggest that channel unit spacing size and sequence are all important in determining hyporheic exchange patterns of upwelling and downwelling though irregularities in the size and spacing of bedforms caused flow nets to be much more complex in surveyed stream reaches than in idealized stream reaches similar trends emerged relating the average geomorphic wavelength to the average hyporheic wavelength in both surveyed and idealized reaches copyright 2005 john wiley sons ltd

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

float transient electromagnetic method in loop transient electromagnetic measurements on lake holzmaar germany lake sediments may serve as archives on paleoclimatic fluctuations geomagnetic field variations and volcanic activities lake holzmaar in eifel germany is a maar lake and its lacustrine sediments provide paleoclimatic proxy data therefore knowledge about the geometry and especially about the thickness of the sediments is very important for determining an optimum drilling location for paleoclimatic studies we have developed a floating in loop transient electromagnetic method field set up float transient electromagnetic method with a transmitter and receiver size of 18 18 m2 and 6 6 m2 respectively this special set up enables in loop transient electromagnetic method measurements on the surface of freshwater lakes that define the geometry and the thickness of sediments beneath such lakes thus helping to determine optimum drilling locations due to the modular design of the new float transient electromagnetic method field set up this system can be handled by two operators and can easily be transported sixteen in loop soundings were carried out on the surface of lake holzmaar the transient electromagnetic method data could not be interpreted by conventional 1d inversions because of the 3d distribution of subsurface conductivity caused by the lake s geometry three dimensional finite element modelling was applied to explain the observed transients and the 3d conductivity distribution beneath the lake was recovered by taking its geometry into account the 3d interpretation revealed approximately 55 m thick sediments beneath 20 m deep water in the central part of the lake

transfer of nonsorbing solutes to a streambed with bed forms theory a theoretical analysis of the exchange of nonsorbing solutes between a permeable streambed and the overlying water of a stream or river is presented in this paper in a companion paper elliott and brooks this issue the results of experimental studies of such exchange are presented the analysis focuses on water movements into within and out of the bed which result from the presence of bed forms ripples and dunes and highlights the mechanisms of pumping and turnover pumping is the movement of fluid through the bed induced by steady dynamic pressure variations over bed forms turnover occurs as moving bed forms trap and release interstitial fluid the detailed analysis was used to generate the distribution of the residence time of solute within the bed which can be used to calculate the net mass exchange due to pumping and turnover

convective transport within stable river sediments local pressure variations of the order of 100 1000 n m2 can be observed between the upstream and downstream faces of the typically triangular shaped dunelike sediment structures that form at the sediment water interface of rivers laboratory experiments were conducted examining the influence of this localized pressure variation on contaminant transport processes within the sediment numerical modeling of the in bed flow via boundary element methods was also undertaken in order to predict convective transport under typical field conditions the laboratory experiments and numerical simulation of the in bed flow in several rivers verified that the pressure distribution observed on the sediment surface and the resulting interstitial fluid convection can control transport of chemically inert nonsorbed contaminants in stable sediments in bed peclet numbers were of the order of 100 1000 indicating the negligible influence of diffusion under the conditions examined

effects of stream discharge alluvial depth and bar amplitude on hyporheic flow in pool riffle channels 1 hyporheic flow results from the interaction between streamflow and channel morphology and is an important component of stream ecosystems because it enhances water and solute exchange between the river and its bed hyporheic flow in pool riffle channels is particularly complex because of three dimensional topography that spans a range of partially to fully submerged conditions inducing both static and dynamic head variations hence these channels exhibit transitional conditions of streambed pressure and hyporheic flow compared to previous studies of fully submerged two dimensional bed forms here we conduct a series of three dimensional simulations to investigate the effects of bed topography depth of alluvium and stream discharge on hyporheic flow in pool riffle reaches with variable bed form submergence and we propose three empirical formulae to predict the mean depth of hyporheic exchange and characteristic values of the residence time distribution mean and standard deviation hyporheic exchange is predicted with a three dimensional pumping model and hyporheic flow is modeled as a darcy flow we find that the hyporheic residence time is well approximated by a lognormal distribution for both partially and entirely submerged pool riffle topography with the parameters of the distribution defined by the mean and variance of the log transformed residence time depth of alluvium has a substantial effect on hyporheic flow when alluvial depth is less than a third of the bed form wavelength for the conditions examined

joint inversion of geophysical data summary by jointly inverting several different kinds of geophysical measurements at a site we avoid some of the ambiguity inherent in the individual methods we show how this can be done for the combination of dc resistivity and magnetotelluric measurements on a layered medium by considering a simple 3 layer model the combination resolves the resistivity of the thin resistive second layer even though neither of the two methods can do so alone the method is then applied to field data from a shallow sedimentary basin a blind zone occurs beneath a thick near surface conductive shale by a study of the eigenvalue structure of the model it can be seen that resolution in this zone would be slightly enhanced by higher frequency magnetotelluric data but additional dc data at larger spacing would yield no improvement

a field test of tubino s 1991 model of alternate bar formation this study investigates the fluvial dynamics of straight natural stream channels in particular this experimental field study quantitatively assesses a physically based non linear mathematical theory of alternate bar formation under unsteady natural flow conditions within a straight alluvial stream the study site is an artificially straightened section of the embarras river located approximately 16 km south of champaign illinois data were collected on channel form gradient alternate bar dimensions bed sediment size and flow stage over a 2 year study period both linear and non linear steady flow hydrodynamic theories suggest that alternate bars are critical to the process of meander development but these theories do not predict bar development for unsteady flow conditions which typically occur in natural alluvial channels tubino 1991 suggests that bar evolution for a flood hydrograph can be divided into three parts 1 a period of limited bar growth during the rising stage of the flood 2 a stage of modest bar decay near the peak of the flood and 3 a stage of non linear bar growth during the prolonged falling stage of the flood bars developed during the falling limb of a hydrograph and exhibited sequential development rather than the uniform growth along the reach predicted by tubino s model as flow stage decreased short low fine grained bars were superimposed on long high and coarser grained bars that developed under preceding high flow stages these results suggest that the process of bar formation in artificially straightened natural streams with heterogeneous bed material may occur under different flow conditions and in a different manner than predicted by theoretical models further work should focus on attempting to isolate the physical mechanisms responsible for alternate bar formation in straight natural streams with heterogeneous bed material and flashy hydrologic flow regimes

effects of stream morphodynamics on hyporheic zone thermal regime 1 we develop a heat transport model to study the impact of streambed morphology on temperature distribution within the hyporheic zone of gravel bed rivers the heat transport model which includes conduction diffusion and advection is solved by a lagrangian approach neglecting transverse dispersion and considering stream water temperature as boundary condition at the streambed first we show that the model accurately reproduces the temperature distribution measured within the hyporheic zone of a reach of the bear valley creek idaho usa our model reveals spatially complex patterns of hyporheic water temperatures that vary with time within the hyporheic zone and at the streambed surface the analysis shows that temperature distributions are primarily related to the hyporheic residence time and consequently to the bed morphology and in stream flow discharge results show that the hyporheic temperature amplitudes are smaller than the surface water temperature and they decrease with stream size leading hyporheic zones of large streams to be independent from in stream daily temperature fluctuations

boat towed radio magnetotellurics a new technique and case study from the city of stockholm we have developed a new data acquisition system and technique to measure the radio magnetotelluric rmt signals from distant radio transmitters with the objective of mapping and modeling electric

using gpr data as constraints in rmt data inversion for water content estimation a case study in heby sweden this study uses ground penetrating radar gpr data as constraints in the inversion of radio magnetotelluric rmt data to provide an improved model at shallow depth we show that modification of the model regularization matrix using all gpr common offset co reflections can mislead the constrained inversion of rmt data to avoid such problems common mid point cmp gpr data are translated to a resistivity model by introducing a new petrophysical relationship based on a combination of topp s and archie s equations this model is updated through a semi iterative method and is employed as an initial and prior model in the subsequent inversion of rmt data finally a water content model that fits the gpr cmp and rmt data is derived from the resistivity model computed by the constrained inversion of rmt data to assess the proposed scheme it is applied to a synthetic data set then real rmt data collected along an 870 m long profile across a known aquifer situated in the north of heby central sweden are inverted by removing the smoothness constraints across gpr co interfaces or using cmp based inversion thick 10 m vadose and saturated zones are resolved and shown to correlate with logs from nearby boreholes nevertheless the application of our cmp based inversion was the only efficient scheme to retrieve thin 3 m saturated zones and the water table at a depth of 7 15 m in the rmt models the estimated models of water content are in good agreement with the available hydrogeological information in the study area

a modelling study of hyporheic exchange pattern and the sequence size and spacing of stream bedforms in mountain stream networks oregon usa studies of hyporheic exchange flows have identified physical features of channels that control exchange flow at the channel unit scale namely slope breaks in the longitudinal profile of streams that generate subsurface head distributions we recently completed a field study that suggested channel unit spacing in stream longitudinal profiles can be used to predict the spacing between zones of upwelling flux of hyporheic water into the stream and downwelling flux of stream water into the hyporheic zone in the beds of mountain streams here we use two dimensional groundwater flow and particle tracking models to simulate vertical and longitudinal hyporheic exchange along the longitudinal axis of stream flow in second third and fourth order mountain stream reaches modelling allowed us to 1 represent visually the effect that the shape of the longitudinal profile has on the flow net beneath streambeds 2 isolate channel unit sequence and spacing as individual factors controlling the depth that stream water penetrates the hyporheic zone and the length of upwelling and downwelling zones 3 evaluate the degree to which the effects of regular patterns in bedform size and sequence are masked by irregularities in real streams we simulated hyporheic exchange in two sets of idealized stream reaches and one set of observed stream reaches idealized profiles were constructed using regression equations relating channel form to basin area the size and length of channel units step size pool length etc increased with increasing stream order simulations of hyporheic exchange flows in these reaches suggested that upwelling lengths increased from 2 7mt o 7 6 m and downwelling lengths increased from 2 9mt o 6 0 m with increase in stream order from second to fourth order step spacing in the idealized reaches increased from 5 3mt o 13 7 m as stream size increased from second to fourth order simulated downwelling lengths increased from 4 3m in second order streams to 9 7 m in fourth order streams with a pool riffle step channel unit sequence and increased from 2 5m to 6 1 m from second to fourth order streams with a pool step riffle channel unit sequence upwelling lengths also increased with stream order in these idealized channels our results suggest that channel unit spacing size and sequence are all important in determining hyporheic exchange patterns of upwelling and downwelling though irregularities in the size and spacing of bedforms caused flow nets to be much more complex in surveyed stream reaches than in idealized stream reaches similar trends emerged relating the average geomorphic wavelength to the average hyporheic wavelength in both surveyed and idealized reaches this article replaces a previously published version hydrological processes 19 17 2915 2929 2005 doi 10 1002 hyp 5790 copyright 2006 john wiley sons ltd

local earthquake le tomography with joint inversion for p and s wave velocities using structural constraints local earthquake le tomography with joint inversion for p and s wave velocities using structural constraints

characterization of heterogeneous near surface materials by joint 2d inversion of dc resistivity and seismic data 1 we have developed a robust 2d joint inversion scheme incorporating the new concept of cross gradients of electrical resistivity and seismic velocity as constraints so as to investigate more precisely the resistivity velocity relationships in complex near surface environments the results of joint inversion of dc resistivity and seismic traveltime data from collocated experiments suggest that one can distinguish between different types or facies of unconsolidated and consolidated materials refining a previously proposed resistivity velocity interrelationship derived from separate inversions of the respective data sets a consistent interpretive structural model can be obtained from the joint inversion models

hyporheic exchange with heterogeneous streambeds laboratory experiments and modeling 1 hyporheic exchange is generally analyzed with the assumption of a homogeneous hyporheic zone in reality streambed sediments have a heterogeneous structure and this natural heterogeneity produces spatially variable interfacial fluxes and complex hyporheic exchange patterns to assess the basic effects of sediment structure on hyporheic exchange we performed salt and dye injection experiments in a recirculating laboratory flume with two heterogeneous sediment beds characterized by negative exponential correlated random hydraulic conductivity fields dye injections showed that the hyporheic flow structure was controlled by the spatial relationship of bed forms to high and low permeability regions of the streambed as no existing model could represent these effects we developed a new finite element model to calculate the pore water flow field resulting from the interaction of the bed form induced boundary head distribution and the heterogeneous sediment structure a numerical particle tracking approach was then used to assess the resulting hyporheic exchange the combined flow transport model did an excellent job of predicting the complex hyporheic flow pathways in the heterogeneous bed and the net hyporheic exchange up to t 30 hours the heterogeneous hydraulic conductivity field caused both greater spatial variability in the water flux through the bed surface and a greater average interfacial flux than would have occurred with a homogeneous bed the layered correlation structure of the streambed produced an effective anisotropy that favored longitudinal pore water flow and caused a relatively rapid decrease of the mean pore water velocity with depth as a result solute penetration into the bed was confined to a more shallow region than would have occurred with a homogeneous bed the combination of faster near surface transport and shallower solute penetration produced a shorter mean hyporheic residence time on the basis of the combination of experimental results and model simulations we conclude that the structural heterogeneity of streambed sediments produces more spatially limited hyporheic exchange that occurs with greater spatial variability and at a higher overall rate

hyporheic zone hydrologic science a historical account of its emergence and a prospectus the hyporheic zone defined by shallow subsurface pathways through river beds and banks beginning and ending at the river is an integral and unique component of fluvial systems it hosts myriad hydrologically controlled processes that are potentially coupled in complex ways understanding these processes and the connections between them is critical since these processes are not only important locally but integrate to impact increasingly larger scale biogeochemical functioning of the river corridor up to the river network scale thus the hyporheic zone continues to be a growing research focus for many hydrologists for more than half the history of water resources research this manuscript partly summarizes the historical development of hyporheic zone hydrologic science as gleaned from papers published in water resources research from the birth of the concept of the hyporheic zone as a hydrologic black box sometimes referred to as transient storage zone to its adolescent years of being torn between occasionally competing research perspectives of interrogating the hyporheic zone from a surface or subsurface view to its mature emergence as an interdisciplinary research field that employs the wide array of state of the art tools available to the modern hydrologist the field is vibrant and moving in the right direction of addressing critical fundamental and applied questions with no clear end in sight in its growth there are exciting opportunities for scientists that are able to tightly link the allied fields of geology geomorphology hydrology geochemistry and ecology to tackle the many open problems in hyporheic zone science

subsurface flow in lowland river gravel bars geomorphic and hydraulic processes which form gravel bars in large lowland rivers have distinctive characteristics that control the magnitude and spatial patterns of infiltration and exfiltration between rivers and their immediate subsurface environments we present a bedform infiltration relation together with a set of field measurements along two reaches of the san joaquin river ca to illustrate the conditions required for infiltration and exfiltration of flow between a stream and its undulating bed and a numerical model to investigate the factors that affect paths and residence times of flow through barforms at different discharges it is shown that asymmetry of bar morphology is a first order control on the extent and location of infiltration which would otherwise produce equal areas of infiltration and exfiltration under the assumption of sinusoidal bedforms hydraulic conductivity varies by orders of magnitude due to fine sediment accumulation and downstream coarsening related to the process of bar evolution this systematic variability not only controls the magnitude of infiltration but also the residence time of flow through the bed the lowest hydraulic conductivity along the reach occurred where the difference between the topographic gradient and the water surface gradient is at a maximum and thus where infiltration would be greatest into a homogeneous bar indicating the importance of managing sand supply to maintain the ventilation and flow through salmon spawning riffles numerical simulations corroborate our interpretation that infiltration patterns and rates are controlled by distinctive features of bar morphology

seismic characterization of fracturing at the aspo hard rock laboratory sweden from the kilometer scale to the meter scale abstract in 1986 the swedish nuclear fuel and waste management co skb decided to build an underground research laboratory the aspo hard rock laboratory hrl the aspo hrl offers the possibility to test and demonstrate a full site investigation sequence as part of this work various seismic techniques were tested and demonstrated from the kilometer to the meter scale the preliminary investigation stage comprised surface reflection profiling and vsp the vsp measurements though limited to one borehole played an important role in defining the site model shallow reflection surveys in crystalline rock have been judged as basically feasible but further development is required to reduce costs during the construction of the laboratory the objective of the seismic investigations was to check and refine the site model within the zone of excavation disturbance experiment project seismic tomographic analyses were made for p and s wave velocity and attenuation at 5 15 m scale crosshole reflection imaging was also performed the tracer retention understanding experiments project also included transmission and reflection tomography but on a 100 300 m scale for the experiments where both transmission and reflection measurements were processed the seismic surveys also produced information regarding the intrinsic mechanical properties of the rock besides inferring a geometrical model of the rock structures

overview of geological and hydrogeological conditions of the aspo hard rock laboratory site abstract the site of the underground facility the aspo hard rock laboratory was excavated at a depth of 450 m below the island of aspo and has been extensively investigated by geological hydrogeological and hydrochemical methods as part of the geoscientific research for disposal of nuclear waste in sweden the geological history of the area dates back to 1 85 ga and is dominated by granitoids belonging to the trans scandinavian igneous belt but also includes basic sheets and xenoliths and dikes of fine grained granite seven tectonic episodes giving rise to fracture mineralization are recognised the major discontinuities and fracture zones were characterised from surface investigations before the tunnel construction work started these structural features were also identified in the tunnel and are as predicted the major water conducting features sets of open fractures in the nnw nw and n s directions and the brittle fine grained granite are other important water conductors groundwater flow modelling shows that the location of aspo island has a major impact on the current distribution of groundwater salinity due to varying hydraulic boundary conditions in the late and post glacial period

coupled 3 d stream flow and hyporheic flow model under varying stream and ambient groundwater flow conditions in a pool riffle system 1 exchange of water and solutes across the stream sediment interface is an important control for biogeochemical transformations in the hyporheic zone hz in this paper we investigate the interplay between turbulent stream flow and hz flow in pool riffle streams under various ambient groundwater flow conditions streambed pressures derived from a computational fluid dynamics cfd model are assigned at the top of the groundwater model and fluxes at the bottom of the groundwater model domain represent losing and gaining conditions simulations for different reynolds numbers re and pool riffle morphologies are performed results show increasing hyporheic exchange flows m3 d for larger re and a concurrent decrease in residence time rt losing and gaining conditions were found to significantly affect the hyporheic flow field and diminish its spatial extent as well as rates of hyporheic exchange flow the fraction of stream water circulating through the hyporheic zone is in the range of 1 10 5 to 1 10 6 per meter stream length decreasing with increasing discharge complex distributions of pressure across the streambed cause significant lateral hyporheic flow components with a mean lateral travel distance of 20 of the longitudinal flow paths length we found that the relationship between pool riffle height and hyporheic exchange flow is characterized by a threshold in pool riffle amplitude beyond which hyporheic exchange flow becomes independent of riffle height hyporheic residence time distributions rtd are log normally distributed with medians ranging between 0 7 and 19 h

macropores as preferential flow paths in meander bends macropores are subsurface connected void spaces caused by processes such as fracture of soils micro erosion and fauna burrows they are common near streams e g hyporheic and riparian zones and may act as preferential flow paths between surface and groundwaters affecting hydrologic and biogeochemical processes we tested the hydrologic function of macropores by constructing an artificial macropore within the saturated zone of a meander bend open macropore om and later filling its upstream end partially filled macropore pfm for each treatment we injected saline tracer at an upgradient monitoring well within the meander and monitored downgradient hydraulics and tracer transport pressure transducers in monitoring wells indicated hydraulic gradients within the meander were 32 higher perpendicular to and 6 higher parallel to the macropore for the om than for the pfm additionally hydraulic conductivities measured via falling head tests were 29 to 550 times higher along the macropore than in nearby sediment we used electrical conductivity probes in wells and electrical resistivity imaging to track solute transport transport velocities through the meander were on average 9 and 21 higher per temporal moment analysis and observed tracer peak respectively for the om than for the pfm furthermore temporal moments of tracer breakthrough analysis indicated downgradient longitudinal dispersion and breakthrough tracer curve tailing were on average 234 and 182 higher for the om respectively this suggests the om enabled solute transport at overall shorter timescales than the matrix but also increased tailing our results demonstrate the importance of macropores to meander bend hydrology and solute transport copyright 2012 john wiley sons ltd