spatio temporal structure of the pentadecadal variability over the north pacific abstract using a multi taper frequency domain singular value decomposition mtm svd a pentadecadal oscillation was detected in the winter spring sea level pressure slp field over the north pacific and surface air temperature in north america which was significant at the 95 confidence level the mtm svd captured the different slp and air temperature distributions between the winter and spring seasons in a consistent manner the pentadecadal slp signature in the spring season is centered nearer the west coast of north america than in the winter season this zonal displacement is consistent with the prominent springtime pentadecadal air temperature variability in mid latitude western north america a wavelet analysis of the pacific decadal oscillation index pdoi showed that the regime shifts in the 1920s 1940s and 1970s involved simultaneous phase reversals of the bidecadal and pentadecadal variations the two interdecadal variations are synchronized with one another such that a half period of the pentadecadal oscillation one epoch of an individual regime corresponds to one and half periods of the bidecadal oscillation these results are consistent with the wavelet analysis of the north pacific index npi similar resonance between the bidecadal and pentadecadal variations is evident in air temperatures over alaska the bidecadal and pentadecadal signals have different seasonality in these time series suggesting that although the two interdecadal variations arise from two different physical mechanisms they interact with each other the most distinct seasonal difference was observed in mid latitude western north america where the bidecadal variation prevails only in the winter season and the pentadecadal variation only in the spring season alaska air temperatures in the winter and winter spring of 1999 were the coldest since 1977 as were springtime air temperatures in mid latitude western north america in contrast to the warm anomalies that prevailed in this region during 1977 98 the npi and pdoi also exhibited an opposite polarity in 1999 to the respective regime mean polarities these anomalous conditions in winter and spring seasons of 1999 may signify a major regime shift in 1998 1999 in order to verify whether or not a regime shift did occur in 1998 1999 a careful examination of additional data in coming ten or so years will be necessary

ground penetrating radar assisted saturation and permeability estimation in bimodal systems near surface investigations often require characterization of vadose zone hydraulic parameters conventional sampling or borehole techniques for estimating these parameters are costly time consuming and invasive all of which limit collection of hydrogeological data at a spacing needed for detailed site characterization incorporation of two or three dimensional densely sampled geophysical data with conventional hydrological data increases the amount of data available for the characterization and thus has the potential to significantly improve the hydraulic parameter estimates over those obtained from borehole data alone the hydraulic estimation procedure can be greatly improved by incorporating dielectric information potentially available from ground penetrating radar gpr a noninvasive high resolution geophysical method the procedures for collecting and processing gpr data in the format needed for the proposed estimation technique are relatively new and still a topic of research our method requires as a starting point the ability to estimate dielectric constants from gpr data numerical experiments were performed to investigate the general utility of the gpr assisted estimation technique under a range of conditions three bimodal systems were investigated each system being composed of a sand facies together with another facies with a larger clay volume fraction each facies was defined using characteristic values of clay content porosity and permeability using dielectric information and petrophysical relations degree of saturation and intrinsic permeability values at each location within the three systems were identified for bimodal systems a dielectric constant measurement corresponds to two possible values of saturation and intrinsic permeability at each location single values of saturation and intrinsic permeability were estimated from these values using the principle of maximum likelihood results from case studies demonstrate that a combination of gpr data with conventional borehole data significantly improves the estimates of saturation and has the potential to improve the estimates of permeability over those obtained from well bore data alone the proposed method should be especially advantageous for vadose zone characterization in areas favorable for gpr data acquisition where detailed hydraulic parameter information is required but the drilling of numerous boreholes is prohibited

pilot scale field validation of the long electrode electrical resistivity tomography method a validation experiment carried out in a scaled field setting was attempted for the long electrode electrical resistivity tomography method in order to demonstrate the performance of the technique in imaging a simple buried target the experiment was an approximately 1 17 scale mock up of a region encompassing a buried nuclear waste tank on the hanford site the target of focus was constructed by manually forming a simulated plume within the vadose zone using a tank waste simulant the long electrode results were compared to results from conventional point electrodes on the surface and buried within the survey domain using a pole pole array both point and long electrode imaging techniques identified the lateral extents of the pre formed plume with reasonable fidelity but the long electrode method was handicapped in reconstructing vertical boundaries the pole dipole and dipole dipole arrays were also tested with the long electrode method and were shown to have the least favourable target properties including the position of the reconstructed plume relativetotheknownplumeandtheintensityoffalsepositivetargets thepoorperformance of the pole dipole and dipole dipole arrays was attributed to an inexhaustive and non optimal coverage of data at key electrodes as well as an increased noise for electrode combinations with high geometric factors however when comparing the model resolution matrix among the different acquisition strategies the pole dipole and dipole dipole arrays using long electrodes were shown to have significantly higher average and maximum values within the matrix than any pole pole array the model resolution describes how well the inversion model resolves the subsurface given the model resolution performance of the pole dipole and dipole dipole arrays it may be worth investing in tools to understand the optimum subset of randomly distributed electrode pairs to produce maximum performance from the inversion model

constraints on hydraulic parameters and implications for groundwater flux across the upland estuary interface abstract analyses of independent laboratory and field scale measurements from two sites on sapelo island georgia reveal heterogeneity in hydraulic parameters across the upland estuary interface regardless of the method used short duration pumping tests amplitude attenuation of tidal pumping data sediment grain size distributions and falling head permeameter tests we obtain hydraulic conductivity of 10 4 m s 1 for the fine grained well sorted clean sands that make up the upland areas proximal to the upland estuary boundary the tidal pumping analyses and permeameter tests suggest that hydraulic conductivities decrease by more than two orders of magnitude a result consistent with the presence of a clogging layer such a clogging layer may arise due to a variety of physical chemical or biological processes the extent and orientation of the layers of reduced hydraulic conductivity near the upland estuary boundary influence the nature of the aquifer s response to tidal forcing where the lower conductivity layer forms a relatively flat creek bank tidal pumping produces a primarily mechanical response in the adjacent aquifer where the creek bank is nearly vertical there is a more direct hydraulic connection between the tidal creek and the adjacent aquifer the clogging layer likely contributes to the development of complicated flow pathways across the upland estuary boundary effective flow paths calculated from tidal pumping data terminate within the marsh beyond the boundary of the upland aquifer suggesting a diffuse regime of groundwater discharge in the marsh we postulate that in many settings submarsh flow may be as important as seepage faces for groundwater discharge into the marsh estuary complex

radiocarbon chronology of the neolithic sites from the boreal zone of european russia and environmental changes based on the last proxy data this article discusses the possible correlation of the neolithisation of western europe with the environmental changes the database of the neolithic sites developed by the radiocarbon laboratory of the institute for history of material culture has been used in the assessment of the frequency of radiocarbon dated sites various isotopic methods have been used for the estimation of holocene environmental changes the comparative analysis reveals the correlation of maxima and minima in the distribution of radiocarbon dated sites with the fluctuations of lake level solar and cosmic ray activities oxygen isotopes and other environmental records

chaotic solute advection by unsteady groundwater flow 1 solute mixing in fluids is enhanced significantly by chaotic advection the phenomenon in which fluid pathlines completely fill the spatial domain explored by a laminar flow steady groundwater flows are in general not well conditioned for this phenomenon because darcy s law confines them spatially to nonintersecting stream surfaces unsteady groundwater flows however may in principle induce chaotic solute advection if their time dependence is periodic and produces frequent reorientation of pathlines an effect connected closely to the development of high solute mixing efficiencies in this paper a simple two dimensional model groundwater system is studied theoretically to evaluate the possibility of inducing chaotic solute advection in the flow field near a recirculation well whose pumping behavior is time periodic in the vernacular of dynamical systems theory the model studied is an example of a hamiltonian system thus allowing a mathematical formulation that facilitates consideration of whether chaotic advection can occur when the model system is driven time periodically by alternate operation of the production and injection components of the recirculation well numerical simulations of the fluid pathlines indicate that regions of chaotic solute advection will indeed develop in the flow field near the well with expected major improvement in plume spreading

tree ring reconstructions of temperature and sea level pressure variability associated with the warm season arctic oscillation since ad 1650 1 arctic oscillation ao changes are inferred from a tree ring reconstruction of a warm season temperature index the reconstruction covers ad 1650 1975 and is based largely on chronologies from circumpolar arctic and circum north atlantic areas it accounts for 48 of the variance in the instrumental ao record from 1900 to 1975 verifies using independent data and exhibits its largest variance at low frequencies positive levels during 20th century periods equal or exceed values back to ad 1650 trends including lower values during little ice age periods resemble those of arctic temperature reconstructions reflecting some data overlap but also the strong link between the ao and northern temperatures a reconstruction of an ao summer sea level pressure index shows similar trends comparison of these reconstructions with proxies of the north atlantic oscillation nao and other indices can help clarify relationships between the ao and nao at least during the boreal warm season

major features and forcing of high latitude northern hemisphere atmospheric circulation using a 110 000 year long glaciochemical series the greenland ice sheet project 2 glaciochemical series sodium potassium ammonium calcium magnesium sulfate nitrate and chloride provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid low latitudes of the northern hemisphere interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants volcanic and biomass burning events storminess over marine surfaces continental aridity and biogenic source strength plus information related to the controls on both high and low frequency climate events of the last 110 000 years climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long term behavior of atmospheric circulation patterns through changes in ice volume sea level events such as the heinrich events massive discharges of icebergs first identified in the marine record that are found to operate on a 6100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics and rapid climate change events massive reorganizations of atmospheric circulation that are demonstrated to operate on 1450 year cycles changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events explanation for the exact timing and global synchroneity of these events is however more complicated preliminary evidence points to possible solar variability climate associations for these events and perhaps others that are embedded in our ice core derived atmospheric circulation records

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

bayesian method for hydrogeological site characterization using borehole and geophysical survey data theory and application to the lawrence livermore national laboratory superfund site a stochastic bayesian approach for combining well logs and geophysical surveys for enhancing subsurface characterization is presented the main challenge we face is in creating the bridge to link between ambiguously related geophysical surveys and well data the second challenge is imposed by the disparity between the scale of the geophysical survey and the scale of the well logs our approach is intended to integrate and transform the well log data to a form where it can be updated by the geophysical survey and this tends to be a convoluted process our approach starts with generating images of the lithology conditional to well logs each lithology image is then used as the basis for generating a series of shaliness images conditional to well log data shaliness images are converted to resistivity images using a site specific petrophysical model relating between shaliness resistivity and lithology to create the necessary interface with the cross well resistivity survey the lithology and resistivity images are then updated using cross well electromagnetic resistivity surveys we explored the limits of the approach through synthetic surveys of different resolutions and error levels employing the relationships between the geophysical and hydrological attributes which are weak nonlinear or both the synthetic surveys closely mimic the conditions at the llnl superfund site we show that the proposed stochastic bayesian approach improves hydrogeological site characterization even when using low resolution resistivity surveys

holocene climate variability as reflected by mid european lake level fluctuations and its probable impact on prehistoric human settlements abstract a data set of 180 radiocarbon tree ring and archaeological dates obtained from sediment sequences of 26 lakes in the jura mountains the northern french pre alps and the swiss plateau was used to construct a holocene mid european lake level record the dates do not indicate a random distribution over the holocene but form clusters suggesting an alternation of lower and higher climatically driven lake level phases they provide evidence of a rather unstable holocene climate punctuated by 15 phases of higher lake level 11 250 11 050 10 300 10 000 9550 9150 8300 8050 7550 7250 6350 5900 5650 5200 4850 4800 4150 3950 3500 3100 2750 2350 1800 1700 1300 1100 750 650 cal bp and after 1394 ad a comparison of this mid european lake level record with the gisp2 polar circulation index pci record the north atlantic ice rafting debris ird events and the 14 c record suggests teleconnections in a complex cryosphere ocean atmosphere system correlations between the gisp2 pci the mid european lake level the north atlantic ird and the residual 14 c records suggest that changes in the solar activity played a major role in holocene climate oscillations over the north atlantic area

tidal dynamics of the water table in beaches tidal motions of the water table height inside a sloping beach are investigated via field measurements and theoretical considerations only the movements forced by the tide are considered so a beach with negligible wave activity was chosen for the field measurements the data show that even in the absence of precipitation the time averaged inland water table stands considerably above the mean sea level also the water table at a fixed point inside the beach is far from sinusoidal even though its variation is forced by an essentially sinusoidal tide this latter effect is due to the boundary condition along the sloping beach face which acts as a highly nonlinear filter the observed behavior of the water table is explained in terms of perturbation extensions to the classical deep aquifer solution one extension deals with the nonlinearity in the interior the other with the boundary condition at the sloping beach face

a two dimensional analytical solution of groundwater response to tidal loading in an estuary a two dimensional transient groundwater flow equation for a confined nonleaky aquifer is solved analytically with an estuary tidal loading boundary condition the amplitude and phase of the tide varies with position and time respectively these variations called the damping coefficient for amplitude and separation constant for phase along the coastline are considered in the analysis the solution presented is more advanced than the traditional one dimensional analytical solution with a one dimensional tidal loading boundary condition the damping coefficient and separation constant in the application study are obtained from the harmonic analysis of the observed tidal level in apalachicola bay florida the analytical solution is compared to a two dimensional finite difference solution a numerical simulation illustrates the response of piezometric head to tidal loading the piezometric head and phase from both solutions match closely the analytical and numerical solutions show that a piezometric head along both sides of the estuary can be predicted given a tidal elevation at the entry of an estuary the fluctuation of piezometric head in response to tidal loading diminishes rapidly inland and diminishes slowly along the coastline of an estuary there are also obvious phase shifts associated with spatial variations as the wave propagates

drought reconstructions for the continental united states abstract the development of a 2 lat 3 long grid of summer drought reconstructions for the continental united states estimated from a dense network of annual tree ring chronologies is described the drought metric used is the palmer drought severity index pdsi the number of grid points is 154 and the reconstructions cover the common period 1700 1978 in producing this grid an automated gridpoint regression method called point by point regression was developed and tested in so doing a near optimal global solution was found for its implementation the reconstructions have been thoroughly tested for validity using pdsi data not used in regression modeling in general most of the gridpoint estimates of drought pass the verification tests used in addition the spatial features of drought in the united states have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design the drought reconstructions show that the 1930s dust bow

recent eurasian river discharge to the arctic ocean in the context of longer term dendrohydrological records 1 mapped correlations between annual discharges ad 1938 1990 of the major eurasian rivers entering the arctic ocean severnaya dvina pechora ob yenisey lena and kolyma demonstrate a positive relationship between discharge and the palmer drought severity index pdsi within the individual basins and more distant areas the relationship between recent discharge and pdsi supports the application of dendrohydrological modeling to produce reconstructions of discharge extending back before the 20th century the dendrohydrologic models explain from 41 yenisey to 55 pechora of the observed variability of flow in the individual basins and 39 of the total combined discharge discharge reconstructions for the period ad 1800 1990 indicate that there is no long term monotonic trend toward higher discharge over the past 200 years reconstructed annual discharge for the individual rivers and the total discharge from all the rivers experienced in the 20th century are within the bounds of natural variability experienced over the past 200 years the s dvina pechora ob and kolyma reconstructions do display significant multidecadal variability in discharge similar to that observed in the north atlantic north pacific and northern hemisphere climatic parameters although the translation of such variability to the river discharges remains uncertain the presence of multidecadal variability makes it more difficult to detect or ascribe annual discharge changes that may be attributable to global warming

role of storm track activity in the interannual seesaw of summer precipitation over northern eurasia 1 oscillation between relatively dry and wet extremes is a noteworthy characteristic of the interannual variability in summer precipitation over siberia recently we identified an out of phase relationship in the temporal signature of basin scale precipitation between eastern and western siberia es and ws this east west seesaw has been especially pronounced during the past 30 years the spatial structure of large scale precipitation and circulation anomalies associated with this east west seesaw is characterized by an east west dipole across northern eurasia we extended our work to investigate the important atmospheric processes involved in the dipole patterns of precipitation and large scale circulation anomalies for the northern summers june august of 1972 2001 in particular this work focuses on the role of storm track activities associated with synoptic scale 10 days eddies in producing the stationary waves that correspond to the precipitation anomaly dipoles linear regression and composite analyses of various eddy statistics are performed for two contrasting extremes in the siberian summer precipitation seesaw these two extreme phases are denoted es wet ws dry and ws wet es dry the summer mean atmospheric anomalies related to the precipitation seesaw show stationary wavetrain patterns in conjunction with the precipitation dipole anomalies the cold trough warm ridge dipole corresponds to the relative wet and dry region analysis of storm track activity reveals similar east west contrasting structures meaning that the displacements associated with the anomalous storm tracks are accompanied by a phase reversal between the two extreme phases an anomalous stationary trough ridge corresponds to the anomalous high low synoptic scale eddy activity region in both es and ws the forcing by synoptic scale eddies is examined to confirm the storm track feedback on the eurasian stationary waves the results show that barotropic feedback induced by synoptic scale eddy vorticity fluxes is in phase with the eurasian wave field cyclonic anticyclonic circulation forcing is collocated with the anomalous stationary trough ridge these spatially coherent relationships suggest that storm track feedback due to eddy vorticity fluxes helps to reinforce and maintain the eurasian wave structure coupled with the precipitation dipole pattern of each phase consequently the interannual variability of the eurasian storm track intensity and location is a crucial factor in forcing the mean precipitation and circulation patterns between the two extreme phases

numerical modeling of subsurface release and fate of benzene and toluene in coastal aquifers subjected to tides abstract a numerical study was undertaken to investigate subsurface release and fate of benzene and toluene in a tidally influenced beach the simulations were conducted by using a numerical model biomarun which coupled a multi monod kinetic model biob to a density dependent variably saturated groundwater flow model marun the fate and transport of the contaminant plume were characterized by computing its centroid trajectory spreading area and percentage of biodegradation in beach saturated and unsaturated zone respectively key factors likely affecting this process were investigated including tide amplitude capillarity and hydraulic conductivity it was found that aerobic biodegradation was the major fate of the contaminant plume in the beach tidal action twisted the centroid of the contaminant plume during its migration in the beach which increased the residence time of the plume in the beach high tidal range significantly altered the spatial distribution of the contaminant biodegradation in the beach in contrast the capillary fringe had impacts on the percentage of benzene biodegraded in the saturated and unsaturated zone of the beach the increase in capillary fringe enhanced the percentage of the contaminant biodegraded in the unsaturated zone up to 40 which is comparable to that in the saturated zone hydraulic conductivity seemed to have large impacts on the biodegradation rate of the contaminant in the beach higher hydraulic conductivity induced faster contaminant biodegradation in the beach

tidal influence on behaviour of a coastal aquifer adjacent to a low relief estuary the tidal influence on groundwater hydrodynamics salt water intrusion and submarine groundwater discharge from coastal estuarine aquifers is poorly quantified for systems with a mildly sloping beach in contrast to the case where a vertical beach face is assumed we investigated the effect of beach slope for a coastal aquifer adjacent to a low relief estuary where industrial waste was emplaced over the aquifer the waste was suspected to discharge leachate towards the estuary field observations at various locations showed that tidally induced groundwater head fluctuations were skewed temporally frequency analysis suggested that the fluctuation amplitudes decreased exponentially and the phase lags increased linearly for the primary tidal signals as they propagated inland salinisation zones were observed in the bottom part of the estuary and near the beach surface flow and transport processes in a cross section perpendicular to the estuary were simulated using seawat 2000 which is capable of depicting density dependent flow and multi species transport the simulations showed that the modelled water table fluctuations were in good agreement with the monitored data further simulations were conducted to gain insight into the effects of beach slope in particular the limiting case of a vertical beach face was considered the simulations showed that density difference and tidal forcing drive a more complex hydrodynamic pattern for the mildly sloping beach than the vertical beach as well as a profound asymmetry in tidally induced water table fluctuations and enhanced salt water intrusion the simulation results also indicated that contaminant transport from the aquifer to the estuary was affected by the tide where for the mildly sloping beach the tide tended to intensify the vertical mass exchange in the vicinity of the shoreline

mapping permeability in heterogeneous aquifers using hydrologic and seismic data a new method is presented for identification of the permeability distribution in near surface aquifers in addition to using the usual sparsely sampled pressure and permeability data the method incorporates densely sampled seismic data as obtained from a reflection or tomography survey along with empirical relationships between seismic and hydraulic properties the procedure is to first estimate by hydrologic inversion a pressure field then the velocity permeability pressure relationship is used to map the inverted pressure and measured seismic data to multivalued estimates of the permeability of those the most probable value based on the hydrologic inversion is selected in synthetic case studies the tremendous increase in coverage offered by the seismic data leads to dramatically better results in terms of both accuracy and resolution an appealing feature is the use of relatively easy to acquire pressure data a second is the incorporation of geophysical data which can sample an entire aquifer remotely without the need for an expensive and invasive drilling program

determination of aquifer transmissivity from earth tide analysis the water level in an open well tapping an artesian aquifer responds to pressure head disturbance caused by earth tide dilatation of the aquifer because a finite amount of time is needed for water to flow into and out of the well there exists a phase shift or time lag between the tidal dilatation of the aquifer and the water level response in the well we derive an analytical solution that expresses the phase shift as a function of the aquifer transmissivity storage coefficient well radius and the period of the harmonic disturbance this solution is rather insensitive to the storage coefficient thus if the phase shift is known for a harmonic disturbance the transmissivity can be calculated given a rough estimate of the storage coefficient theoretical analysis shows that a significant phase shift may be present even if the disturbance is slowly varying as in the case of earth tides this opens the possibility of estimating aquifer transmissivity from water level records that show earth tide fluctuations a case study using data from a site near parkfield california is presented to illustrate application of the theory phase shifts of the o1 25 82 hour period and m2 12 42 hour period tidal constituents are chosen for analysis because they are free of systematic contamination by fluctuations in barometric pressure a brief error analysis suggests that the computed o1 phase shift is subject to large uncertainty while the computed m2 phase shift is substantially more accurate based on an assumed storage coefficient range of 10 4 to 10 6 the estimated transmissivity range is 8 10 6 to 2 10 5 m2 s while hydraulic tests have not been performed to validate these estimates the range is consistent with the transmissivity value determined by other investigators from analysis of the water level response to an earthquake

comment on plume spreading in groundwater by stretching and folding by d c mays and r m neupauer the recent paper of mays and neupauer 2012 presents one such novel methodology for the acceleration of plume spreading with punctuated injection protocols that result in fluid stretching and folding which are the hallmarks of chaotic dynamics in continuous systems this protocol shows excellent promise as a means to accelerate dispersion for groundwater remediation recovery and so on our comment regarding this paper does not directly pertain to this method but rather corrects an erroneous statement that has important implications for a wide class of intervention methods which involve recycled injection whereby extracted fluid is reinjected elsewhere in the subsurface to impart continuous fluid flow and deformation

plume spreading in groundwater by stretching and folding 1 this paper proposes a new approach to the hydraulics of in situ groundwater remediation in situ remediation promotes reactions between an injected treatment solution and the contaminated groundwater but without a hydraulic mechanism to promote spreading the laminar flows characteristic of porous media will keep the two fluids in approximately the same relative configuration as they travel through the aquifer limiting the opportunity for reactions to occur to address this fundamental limitation this paper borrows a key result from the fluid mechanics literature spreading in laminar flows is optimized by chaotic advection previous studies have applied this result to groundwater remediation using the pulsed dipole model but that model depends on reinjection of fluid which presents a number of theoretical and practical limitations accordingly this paper proposes a new conceptual model for plume spreading by chaotic advection using an engineered sequence of extractions and injections of clean water at an array of wells which generates plume spreading by stretching and folding the fluid interface between the injected treatment solution and the contaminated groundwater but does not require reinjection the paper includes an overview of the analytical techniques poincare sections periodic points stable and unstable manifolds heteroclinic points and lyapunov exponents used to demonstrate chaotic advection in the limiting case in which diffusion is negligible numerical simulations show that spreading by stretching and folding is complimentary to spreading resulting from aquifer heterogeneity

a general analytical solution for groundwater fluctuations due to dual tide in long but narrow islands 1 this paper develops a general mathematical model for describing head fluctuations in an aquifer of long but narrow islands subject to a dual tide effect the upper boundary condition of the aquifer is represented by an equation combining the simplified free surface equation with a leakage term such an equation is considered as a general expression representing the upper boundary condition of a confined unconfined or leaky confined aquifer the closed form solution of the model represented by two series terms is developed by the direct fourier method and finite fourier sine transform one of the series can reduce to a closed form expression by means of contour integral and residue theorem if the width of the island is very large this solution gives the predicted head almost the same as that of the solution for an aquifer subject to a single tide effect it is found that the presence of an upper aquitard produces significant vertical flow in the lower leaky confined aquifer even if the aquitard permeability is low neglecting such vertical flow may result in an overestimate of hydraulic head in the leaky confined aquifer the attenuation factor and phase lag predicted from the present solution subject to the dual tide effect agree well with those estimated from 57 day head fluctuation data observed at garden island australia

a 930 year ring width chronology from moisture sensitive white spruce picea glauca moench in northwestern canada a 930 year tree ring chronology was constructed from living and subfossil white spruce picea glauca moench from the campbell dolomite upland northwest territories canada response function analy sis using climate data from nearby inuvik indicates that 69 of the variation in ring widths can be explained by monthly precipitation and temperature ring width is most strongly correlated with high precipitation between february and may there is also a significant negative relationship between ring widths and tempera tures during the previous growing season periods of slow radial growth at ad 1820 1855 1700 1710 1585 1610 1395 1405 1260 1300 and 1125 1170 are assumed to be associated with times of increased moisture stress periods of rapid growth at ad 1925 1940 1770 1780 1725 1740 1510 1560 1215 1260 and 1185 1205 likely reflect higher precipitation and or decreased moisture stress this chronology is the oldest yet published from northwestern canada and the first that provides a dendrohydrolo

tidal influence on self potential measurements long term surface and borehole self potential sp monitoring was conducted in the uk chalk aquifer at two sites the coastal site is c 1 7 km from the coast and the inland site is c 80 km from the coast at both sites power spectral density analysis revealed that sp data contain the main ocean tidal periodic components however the principal lunar component m2 the dominant ocean tidal component was most significant at the coastal site the m2 signal in surface referenced sp data at the inland site was partly due to telluric currents caused by the geomagnetic ocean dynamo earth and or atmospheric tides also contributed as the sp power spectrum was not typical of a telluric electric field the m2 component in borehole referenced data at the inland site was below the significance level of the analysis method and was two orders of magnitude smaller than the m2 signal in borehole referenced sp data at the coastal site the tidal response of the sp data in the coastal borehole is therefore primarily driven by ocean tides these cause changes in fluid pressure and chemical concentration gradients within the coastal aquifer leading to time varying electrokinetic and exclusion diffusion potentials borehole referenced sp measurements could be used to characterize and monitor tidal processes in coastal aquifers such as the intrusion of seawater

structural characterization of an island aquifer via tidal methods 1 a set of water level time series collected along a transect through a sedimentary island aquifer was used to test the utility of various simple models of ocean tidal propagation in bounded one dimensional aquifers fourier spectra were calculated for the ocean tidal modes and compared with spectra measured in wells along the island transect other sources of fluctuation could be neglected an observed spatial bias in the well responses attenuations and lags could not be modeled by a homogeneous aquifer theory a theory involving composite heterogeneity accounted well for the spatial bias yielding estimates of aquifer transmissivities and storage coefficients indicating a fivefold difference in hydraulic diffusivity along the transect a lack of well locations toward one end of the transect reduced the statistical significance of this result with correlations between regression parameters evident at the same time a second bias was seen involving the ratio of signal amplitude and lag with penetration distance into the aquifer as observed in prior tidal studies a brief set of numerical experiments showed that horizontal layering in aquifer properties was the most probable cause of this propagation bias application of these results to the island data set supported a conceptual stratigraphic model of a highly conductive sloping stratum underlying a less conductive superficial sand layer this model is inconsistent with well logs along the island transect but is supported by additional off transect well logs it was concluded that one dimensional tidal propagation models may be useful in inverse characterization of aquifers with macroscale hydrogeological structures and that the analysis of measured propagation bias has the potential to yield extra information on aquifer properties in the vertical direction

improving degradation of emerging organic compounds by applying chaotic advection in managed aquifer recharge in randomly heterogeneous porous media improving degradation rates of emerging organic compounds eocs in groundwater is still a challenge although their degradation is not fully understood it has been observed that some substances are preferably degraded under specific redox conditions the coupling of managed aquifer recharge with soil aquifer remediation treatment by placing a reactive layer containing organic matter at the bottom of the infiltration pond is a promising technology to improve the rate of degradation of eocs its success is based on assuming that recharged water and groundwater get well mixed which is not always true it has been demonstrated that mixing can be enhanced by inducing chaotic advection through extraction injection engineering in this work we analyze how chaotic advection might enhance the spreading of redox conditions with the final aim of improving degradation of a mix of benzotriazoles benzotriazole 5 methyl benzotriazole and 5 chloro benzotriazole the degradation of the first two compounds was fastest under aerobic conditions whereas the third compound was best degraded under denitrification conditions we developed a reactive transport model that describes how a recharged water rich in organic matter mixes with groundwater how this organic matter is oxidized by different electron acceptors and how the benzotriazoles are degraded attending for the redox state the model was tested in different scenarios of recharge both in homogenous and in heterogenous media it was found that chaotic flow increases the spreading of the plume of recharged water consequently different redox conditions coexist at a given time facilitating the degradation of eocs

groundwater flow to a general well configuration in an unconfined aquifer overlying a fractured bedrock abstract unconfined aquifers sometimes overlie fractured bedrocks consisting of unconfined fractured aquifer systems pumping induced hydrodynamics in such aquifer systems has not received much attention as in other types of aquifer systems this paper aims to obtain semi analytical solutions of flow to a general well configuration in such an unconfined fractured two layer aquifer system the examples of general well configuration specifically discussed here include 1 a horizontal well 2 a vertical well 3 a vertical well with one horizontal collector and 4 a vertical well with two horizontal collectors which are perpendicular with each other the methodology is general and can be extended to other types of wells with minor modifications of solutions developed in this study the point sink source solution is first obtained using double infinite fourier and laplace transformations where sink is for pumping and source is for injection the line sink source solution is then obtained via integrating the point sink source along the desired direction and following the principle of superposition the de hoog numerical inverse laplace transform and gaussian quadrature are used to obtain time domain dimensionless drawdown solutions the instantaneous drainage of water table and the inter porosity flow of the underlying fractured aquifer are taken into account the effects of the length of horizontal well on dimensionless drawdown and dimensionless drawdown derivative and scaled sensitivity of the hydraulic parameters of the underlying fractured aquifer are explored the dimensionless drawdowns and drawdown derivatives of a vertical pumping well a vertical well with a single horizontal collector and a vertical well with two perpendicular horizontal collectors are also compared the scaled sensitivity of dimensionless drawdown to the hydraulic parameters of the underlying fractured aquifer of these different pumping well structures is explored the results of this study can be used to evaluate the hydraulic parameters using the drawdown data collected during a pumping test performed in a general well configuration in a unconfined fractured two layer aquifer system furthermore the presented solutions can be utilized to design the pumping well to minimize drawdown in low permeability or thin aquifers by eliminating the inter porosity flow term from the underlying fractured aquifer the solutions are applicable to groundwater flow to a pumping well in leaky aquifers

application of genetic algorithm technique to inverse modeling of tide aquifer interaction modeling of tide aquifer interaction plays a vital role in the management of coastal aquifer systems a novel and robust methodology is presented in this paper for estimating aquifer parameters of coastal aquifers from tide aquifer interaction data using tide aquifer interaction model and genetic algorithm ga two stand alone computer programs were developed to optimize hydraulic diffusivities of unconfined and confined coastal aquifers at multiple sites using ga technique and tide aquifer interaction model and considering two approaches lumped tidal component approach and multi tidal component approach five sets of real world tide aquifer interaction data at two sites of an unconfined aquifer and one set of tide aquifer interaction data at three sites of a confined aquifer were used to demonstrate the efficacy of the methodology the analysis of the ga based inverse modeling results indicated that the multi tidal component approach yields more accurate and reliable hydraulic diffusivities for the unconfined aquifer rmse 0 0129 0 0521 m nse 0 70 0 97 and d1 0 91 0 99 as well as for the confined aquifer rmse 0 0204 0 0545 m nse 0 95 0 97 and d1 0 99 compared with the lumped tidal component approach a comparative evaluation of data size revealed that the short duration datasets of the unconfined aquifer provide more reliable estimate of hydraulic diffusivity than the long duration datasets further it was found that the spring and neap tidal data yield unreasonable values of hydraulic diffusivity with considerably high values of rmse and very low values of r 2 nse and d1 thereby suggesting that spring and neap tidal data are not suitable for aquifer parameter estimation overall it is concluded that the ga based tide aquifer interaction model following multi tidal component approach is the most efficient tool for estimating aquifer parameters of unconfined and confined aquifers from tide aquifer interaction data the developed methodology is also applicable to other coastal basins of the world irrespective of hydrogeological settings

hydrometeorological reconstructions for northeastern mongolia derived from tree rings 1651 1995 reconstructions of annual prior august current july precipitation and streamflow 345 yr in length 1651 1995 are presented for northeastern mongolia based on tree ring width data these precipitation and streamflow reconstructions account for 54 and 48 of the respective variance in instrumental data over the past 50 years variations in instrumental precipitation and streamflow are within the range of those reconstructed over the length of tree ring records however there appear to be more frequent extended wet periods during the twentieth century multitaper spectral analysis revealed statistically significant peaks at 10 8 and 12 8 yr for the precipitation reconstruction and at 12 8 and 20 3 23 8 yr for the streamflow reconstruction similarly singular spectrum analysis identified spectral modes of variation at 12 and 21 yr for both series these spectra resemble those found for tree ring based precipitation reconstructions in central china as well as the western united states and may reflect solar influences on the climate of mongolia

multidecadal variability of north atlantic temperature and salinity during the twentieth century abstract substantial changes occurred in the north atlantic during the twentieth century here the authors demonstrate through the analysis of a vast collection of observational data that multidecadal fluctuations on time scales of 50 80 yr are prevalent in the upper 3000 m of the north atlantic ocean spatially averaged temperature and salinity from the 0 300 and 1000 3000 m layers vary in opposition prolonged periods of cooling and freshening warming and salinification in one layer are generally associated with opposite tendencies in the other layer consistent with the notion of thermohaline overturning circulation in the 1990s widespread cooling and freshening was a dominant feature in the 1000 3000 m layer whereas warming and salinification generally dominated in the upper 300 m except for the subpolar north atlantic where complex exchanges with the arctic ocean occur the single signed basin scale pattern of multidecadal variability is evident from decadal 1000 3000 m temperature and salin

an analytical solution and case study of groundwater head response to dual tide in an island leaky confined aquifer 1 this paper presents an analytical solution of groundwater head response to dual tide fluctuation in the transect of an island leaky aquifer system comprising a confined aquifer and its overlying semipermeable confining layer both layers terminate at the coastlines on two sides of the island solution analysis indicates that the tidal waves from the two sides of the island transect interfere at the middle of the island and the interference decreases to zero as the horizontal length of the aquifer increases to infinity the leakage of the overlying confining layer enhances the landward attenuation of the tidal head fluctuation and shortens the time lag between the head and tide fluctuations the solution agreed well with the observations in eight piezometers in garden island on the continental shelf of western australia reported by trefry and bekele 2004

tide induced groundwater level fluctuation in a u shaped coastal aquifer summary the prediction of groundwater level fluctuation due to tidal waves propagation in coastal aquifers is important for the planning and management of water resources in coastal areas a two dimensional 2 d analytical solution is derived to describe the tidal groundwater fluctuation in an aquifer bounded by three water land boundaries that form a u shaped coastline two opposite sides represent estuary land boundaries on which the amplitude attenuation and phase shift of the tidal movement in the estuary are considered while the third side is an ocean land boundary the effects of wave interaction due to the propagation of oscillating oceanic tides in the cross shore direction inland and the transmission of the two opposite estuarine tides in the along shore direction are investigated three existing head fluctuation solutions can be considered as special cases of the present solution one is for one dimensional flow and the other two are for 2 d flow a transition distance ranging from 10 to 15 times of tidal propagation length along the shoreline can be estimated based on the solution this distance can be used to judge whether the interaction among tides is significant the influences of hydraulic properties on the tidal fluctuations within the aquifer can therefore be assessed quantitatively based on sensitivity analyses one can conclude that the tidal head is most sensitive to the transmissivity and storativity of the aquifer and least to the damping coefficient of tidal amplitude and wave number along the estuary the sensitivities of head fluctuation to the changes of transmissivity and storativity depend on the shoreline length and whether the interaction among waves is significant on the other hand the sensitivities of head fluctuation to the changes of damping coefficient and wave number increase with diagonal distance from the entry of estuary and reach the largest magnitude near the estuary far away seashore

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

dilution of the northern north atlantic ocean in recent decades declining salinities signify that large amounts of fresh water have been added to the northern north atlantic ocean since the mid 1960s we estimate that the nordic seas and subpolar basins were diluted by an extra 19 000 5000 cubic kilometers of freshwater input between 1965 and 1995 fully half of that additional fresh water about 10 000 cubic kilometers infiltrated the system in the late 1960s at an approximate rate of 2000 cubic kilometers per year patterns of freshwater accumulation observed in the nordic seas suggest a century time scale to reach freshening thresholds critical to that portion of the atlantic meridional overturning circulation

saltwater freshwater mixing fluctuation in shallow beach aquifers abstract field measurements and numerical simulations demonstrate the existence of an upper saline plume in tidally dominated beaches the effect of tides on the saltwater freshwater mixing occurring at both the upper saline plume and lower salt wedge is well understood however it is poorly understood whether the tidal driven force acts equally on the mixing behaviours of above two regions and what factors control the mixing fluctuation features in this study variable density saturated unsaturated transient groundwater flow and solute transport numerical models are proposed and performed for saltwater freshwater mixing subject to tidal forcing on a sloping beach a range of tidal amplitude fresh groundwater flux hydraulic conductivity beach slope and dispersivity anisotropy are simulated based on the time sequential salinity data the gross mixing features are quantified by computing the spatial moments in three different aspects namely the centre point length and width and the volume or area in a two dimensional case simulated salinity distribution varies significantly at saltwater freshwater interfaces mixing characteristics of the upper saline plume greatly differ from those in the salt wedge for both the transient and quasi steady state the mixing of the upper saline plume largely inherits the fluctuation characteristics of the sea tide in both the transverse and longitudinal directions when the quasi steady state is reached on the other hand the mixing in the salt wedge is relatively steady and shows little fluctuation the normalized mixing width and length mixing volume and the fluctuation amplitude of the mass centre in the upper saline plume are in general one magnitude order larger than those in the salt wedge region in the longitudinal direction tidal amplitude fresh groundwater flux hydraulic conductivity and beach slope are significant control factors of fluctuation amplitude in the transverse direction tidal amplitude and beach slope are the main control parameters very small dispersivity anisotropy e g l t 5 could greatly suppress mixing fluctuation in the longitudinal direction this work underlines the close connection between the sea tides and the upper saline plume in the aspect of mixing thereby enhancing understanding of the interplay between tidal oscillations and mixing mechanisms in tidally dominated sloping beach systems

groundwater response to tidal fluctuation in a two zone aquifer summary a coastal aquifer may consist of two zones of distinctly different hydraulic properties with the coastal zone of limited width and the inland zone of infinite width the analytical solutions for groundwater level response to tidal fluctuation in such a two zone aquifer are derived and the underlying physical meanings are discussed a dimensionless zone contrast parameter r is introduced which is controlled by ratio between the product of the transmissivity and storativity of the inland zone and that of the coastal zone in the coastal zone the amplitude of groundwater head fluctuation attenuates more quickly when r becomes greater the amplitude declines exponentially with distance from the coastline and the phase lag increases linearly only when r 1 in the inland zone however the head fluctuation always exhibits an exponential attenuation of the amplitude and a linear increase of the phase lag for any value of r thus the diffusivity of the inland zone can be readily assessed with measurements of fluctuation amplitudes or lags as are frequently used when estimating aquifer parameters in homogeneous aquifers compared with jacob 1950 solution for a semi infinite homogeneous aquifer the existence of the coastal zone reduces the amplitude in the inland zone by a spatially constant coefficient and increases the phase lag by a spatially constant shift inverse estimation of aquifer parameters are discussed based on the analytical solutions the analytical solutions are used to estimate the aquifer parameters in a coastal two zone aquifer located in the west part of dongzhai harbor hainan province china

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

a well verified multiproxy reconstruction of the winter north atlantic oscillation index since a d 1400 abstract a new well verified multiproxy reconstruction of the winter north atlantic oscillation nao index is described that can be used to examine the variability of the nao prior to twentieth century greenhouse forcing it covers the period a d 1400 1979 and successfully verifies against independent estimates of the winter nao index from european instrumental and noninstrumental data as far back as 1500 the best validation occurs at interannual timescales and the weakest at multidecadal periods this result is a significant improvement over previous proxy based estimates which often failed to verify prior to 1850 and is related to the use of an extended reconstruction model calibration period that reduced an apparent bias in selected proxies associated with the impact of anomalous twentieth century winter nao variability on climate teleconnections over north atlantic sector land areas although twentieth century nao variability is somewhat unusual comparable periods of persistent positive phase

two dimensional flow response to tidal fluctuation in a heterogeneous aquifer aquitard system in alluvial coastal aquifers finer sediments are preferentially deposited along the downstream direction so the hydraulic conductivity is generally heterogeneous and changes with distance from the coastline to investigate the influence of aquifer heterogeneity on seawater groundwater interaction a new two dimensional model characterising groundwater flow in an aquifer aquitard system was developed assuming that the hydraulic conductivity of the aquifer linearly increases with the distance from the coastline along the inland direction a closed form analytical solution was derived using the separation of variables method comparing the new solution with the numerical solution by comsol multiphysics sweden based on the finite element method one can see that the new solution agreed with the numerical solution very well except at the early time we found that both aquitard leakance and the heterogeneity factor b could result in the propagation bias the propagation bias represents the inconsistency between the theoretical calculation and the observed strong attenuation and small time lag between the head and tide fluctuations the attenuation decreased with perpendicular distance from the coastline x axis whereas the time lag increased with distance along the x axis the relationship between the time lag and the distance along the x axis seemed to be linear when b was 0 001 m 1 whereas it obeyed a power function when b was greater than 0 01 m 1 copyright 2014 john wiley sons ltd

a stochastic approach to the characterization of lithofacies from surface seismic and well data heterogeneity of natural geologic formations strongly influences groundwater flow and contaminant migration this study presents a formal stochastic approach for the integration of surface seismic data and well data into the identification of the spatial arrangement location geometry and interconnectedness of lithofacies and incorporating this information in the estimation of the log permeability probability density function pdf to achieve this goal normal move out nmo corrections are applied to the seismic reflection data to estimate interval seismic velocities calibration curves constructed from the well logs transform these velocity estimates into a lithology indicator prior probability field from the well data and the indicator prior probability field the indicator covariance function and its associated confidence limits are computed neighboring lithology logs and the indicator covariance function are then combined to update the indicator probability field the conditional log permeability pdf is finally computed by weighting the log permeability distribution of each lithology with respect to its indicator probability field the effectiveness of the proposed procedure is shown to depend on the quality of the seismic data and the degree of correlation between seismic and hydrogeologic soil properties a synthetic case study is performed which shows that the surface seismic and well data complement each other with optimal results achieved when both types of data are incorporated into a joint identification procedure

an effective bayesian model for lithofacies estimation using geophysical data 1 a bayesian model coupled with a fuzzy neural network bfnn is developed to enhance the use of geophysical data in lithofacies estimation prior estimates are inferred from borehole lithofacies measurements using indicator kriging and posterior estimates are obtained by updating the prior using geophysical data the novelty of this study lies in the use of the fuzzy neural network for the inference of the likelihood function this allows spatial correlation of lithofacies as well as nonlinear cross correlation between lithofacies and geophysical attributes to be incorporated into lithofacies estimation the effectiveness of bfnn is demonstrated using synthetic data emulating measurements at the lawrence livermore national laboratory llnl site

groundwater dynamics due to general stream fluctuations in an unconfined single or dual porosity aquifer subjected to general areal recharge abstract analytical solutions of groundwater dynamics in an elongated aquifer subjected to general time dependent recharge are presented the lateral boundaries are specified heads with the head variations governed by general time dependent functions general recharge function was not considered in previous works of this kind both single and double porosity aquifers are considered the solution is obtained using fourier sine and laplace transformations followed by an inverse fourier laplace transform involving residue theorem and convolutional integral for the unconfined single porosity aquifer case the exact time domain solution is obtained using the residue theorem for the unconfined double porosity aquifer case the time domain head is calculated using the de hoog inverse laplace algorithm the presented solution can be used to estimate the hydraulic parameters of 1 groundwater head variation of a river basin aquifer subjected to general lateral head variation and recharge 2 groundwater head variation in a double porosity elongated fractured anticline 3 groundwater depletion of an elongated fractured anticline subjected to recharge due to rainfall or snowmelt to its adjacent alluvial aquifer in addition the presented solution can be utilized to optimize the irrigation pattern in a cropland between two trench drains to control the groundwater mound

engineered injection and extraction to enhance reaction for improved in situ remediation 1 during in situ remediation a treatment solution is often injected into a contaminated aquifer to degrade the groundwater contaminant since contaminant degradation reactions occur only at locations where the treatment solution and groundwater contaminant overlap mixing of the treatment solution and the contaminated groundwater is necessary for reaction to occur mixing results from molecular diffusion and pore scale dispersion which operate over small length scales thus mixing during in situ remediation can only occur where the separation distance between the treatment solution and contaminated groundwater is small to promote mixing advection can be used to spread the treatment solution into the contaminated groundwater to increase the extent of the region where the two solutions coexist a certain degree of passive spreading is the natural consequence of aquifer heterogeneity which is manifested as macrodispersion an alternative mechanism is active spreading in which unsteady flows lead to stretching and folding of plumes active spreading can be accomplished by engineered injection and extraction eie in which clean water is injected and extracted at wells surrounding a contaminant plume to create unsteady flow fields that stretch and fold the treatment solution and contaminant plumes for a model system in which nested plumes of two reactants undergo scalar transport and instantaneous reaction the simulation results reported here indicate that eie enhances degradation of groundwater contamination in homogeneous and heterogeneous aquifers compared to baseline models without eie furthermore this study shows that the amount of reaction provided by the spreading due to eie is greater than the amount of reaction due to spreading from heterogeneity alone

the alps with little ice evidence for eight holocene phases of reduced glacier extent in the central swiss alps glacially deformed pieces of wood organic lake sediments and clasts of reworked peat have been collected in front of alpine glaciers since ad 1990 the palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today s shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers glacial transport of the material is indicated by wood anatomy incorporated silt sand and gravel particles missing bark and deformed treerings a total of 65 samples have been radiocarbon dated so far and clusters of dates provide evidence of eight phases of glacier recession 9910 9550 9010 7980 7250 6500 6170 5950 5290 3870 3640 3360 2740 2620 and 1530 1170 calibrated years bp allowing for the timelag between climatic fluctuations glacier response and vegetation colonization these recession phases may lag behind climatic changes by 100 200 years

on the long term context for late twentieth century warming 1 previous tree ring based northern hemisphere temperature reconstructions portray a varying amplitude range between the medieval warm period mwp little ice age lia and present we describe a new reconstruction developed using largely different methodologies and additional new data compared to previous efforts unlike earlier studies we quantify differences between more traditional std and regional curve standardization rcs methodologies concluding that rcs is superior for retention of low frequency trends continental north american versus eurasian rcs series developed prior to merging to the hemispheric scale cohere surprisingly well suggesting common forcing although there are notable deviations e g fifteenth to sixteenth century results indicate clear mwp warm lia cool and recent warm episodes direct interpretation of the rcs reconstruction suggests that mwp temperatures were nearly 0 7c cooler than in the late twentieth century with an amplitude difference of 1 14c from the coldest 1600 1609 to warmest 1937 1946 decades however we advise caution with this analysis although we conclude as found elsewhere that recent warming has been substantial relative to natural fluctuations of the past millennium we also note that owing to the spatially heterogeneous nature of the mwp and its different timing within different regions present palaeoclimatic methodologies will likely flatten out estimates for this period relative to twentieth century warming which expresses a more homogenous global fingerprint therefore we stress that presently available paleoclimatic reconstructions are inadequate for making specific inferences at hemispheric scales about mwp warmth relative to the present anthropogenic period and that such comparisons can only still be made at the local regional scale

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

estimating hydraulic properties of coastal aquifers using wave setup summary wave setup is the elevated mean water table at the coast associated with the momentum transfer of wave breaking which occurs generally over several days groundwater responses to wave setup were observed as far as 5 km inland in central maui hawaii the analysis showed that at times of energetic swell events wave driven water table overheights dominate low frequency groundwater fluctuations associated with barometric pressure effects matching peak frequencies at 1 7 10 6 hz and 3 7 10 6 hz were identified in setup and observed head using spectral decomposition similar to tides the setup propagation through the aquifer shows exponentially decreasing amplitudes and linearly increasing time lags due to the longer periods of setup oscillations the signal propagates deeper into the aquifer 10 km in central maui than diurnal tides 5 km and can therefore provide information on greater length scales hydraulic diffusivity was estimated based on the setup propagation an effective diffusivity of 2 3 107 m2 d is consistent with aquifer parameters based on aquifer tests and tides a one dimensional numerical model supports the results of the analytical solution and strengthens the suitability to estimate hydraulic parameters from setup propagation the methodology is expected to be beneficial to high permeability coastal environments such as on volcanic islands and atolls

chaotic advection and reaction during engineered injection and extraction in heterogeneous porous media during in situ remediation of contaminated groundwater a treatment solution is often injected into the contaminated region to initiate reactions that degrade the contaminant degradation reactions only occur where the treatment solution and the contaminated groundwater are close enough that mixing will bring them together degradation is enhanced when the treatment solution is spread into the contaminated region thereby increasing the spatial extent of mixing and degradation reactions spreading results from local velocity variations that emerge from aquifer heterogeneity and from spatial variations in the external forcings that drive flow certain patterns in external forcings have been shown to create chaotic advection which is known to enhance spreading of solutes in groundwater flow and other laminar flows this work uses numerical simulations of flow and reactive transport to investigate how aquifer heterogeneity changes the qualitative and quantitative aspects of chaotic advection in an aquifer and the extent to which these changes enhance contaminant degradation we generate chaotic advection using engineered injection and extraction eie an approach that uses sequential injection and extraction of water in wells surrounding the contaminated region to create time dependent flow fields that promote plume spreading we demonstrate that as the degree of heterogeneity increases both plume spreading and contaminant degradation increase however the increase in contaminant degradation is small relative to the increase in plume spreading our results show that the combined effects of eie and heterogeneity produce substantially more stretching than either effect separately

the dipole flow test a new single borehole test for aquifer characterization a new single borehole measurement technique for confined aquifers the dipole flow test yields the vertical distributions of the horizontal hydraulic conductivity the vertical hydraulic conductivity and the specific storativity when applied to different borehole intervals the test utilizes straddle packers to isolate two chambers in the borehole pressure transducers to monitor drawdown in them and a small pump to create a dipole flow pattern in the aquifer by pumping water at a constant rate from the aquifer into one chamber transferring it within the well to the next chamber and finally injecting it back to the aquifer a mathematical model describing the drawdown in each chamber is derived for the transient as well as the steady state cases the aquifer parameters may be estimated from data produced by the dipole flow test alone or in conjunction with conventional pumping tests the dipole flow regime reaches a steady state relatively quickly especially in well permeable aquifers a robust computational methodology for estimating the aquifer parameters suitable for automatization is based on the newton raphson algorithm applied to a system of up to three nonlinear equations each describing the well drawdown at a different judiciously chosen time due to the relatively small drawdownmore it invokes the dipole flow test may be applicable to unconfined aquifers as well less

response of the water level in a well to earth tides and atmospheric loading under unconfined conditions the response of the water level in a well to earth tides and atmospheric loading under unconfined conditions can be explained if the water level is controlled by the aquifer response averaged over the saturated depth of the well because vertical averaging tends to diminish the influence of the water table the response is qualitatively similar to the response of a well under partially confined conditions when the influence of well bore storage can be ignored the response to earth tides is strongly governed by a dimensionless aquifer frequency q u the response to atmospheric loading is strongly governed by two dimensionless vertical fluid flow parameters a dimensionless unsaturated zone frequency r and a dimensionless aquifer frequency qu the differences between q u and qu are generally small for aquifers which are highly sensitive to earth tides when q u and qu are large the response of the well to earth tides and atmospheric loading approaches the static response of the aquifer under confined conditions at small values of q u and qu well response to earth tides and atmospheric loading is strongly influenced by water table drainage when r is large relative to qu the response to atmospheric loading is strongly influenced by attenuation and phase shift of the pneumatic pressure signal in the unsaturated zone the presence of partial penetration retards phase advance in well response to earth tides and atmospheric loading when the theoretical response of a phreatic well to earth tides and atmospheric loading is fit to the well response inferred from cross spectral estimation it is possible to obtain estimates of the pneumatic diffusivity of the unsaturated zone and the vertical hydraulic conductivity of the aquifer

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

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

determination of fluid flow properties from the response of water levels in wells to atmospheric loading the water level in a well that taps a partially confined aquifer is often sensitive to atmospheric loading the magnitude and character of this response is partly governed by the well radius the lateral hydraulic diffusivity of the aquifer the thickness and vertical pneumatic diffusivity of the unsaturated zone and the thickness and vertical hydraulic diffusivity of the saturated zone overlying the aquifer these key elements can be combined into five dimensionless parameters that partly govern the phase and attenuation of the response in many cases the response of a well to atmospheric loading can be broken up into a high intermediate and low frequency response the high frequency response is governed largely by the well radius and lateral diffusivity of the aquifer the intermediate frequency response is governed by the loading efficiency of the aquifer the low frequency response is governed by the vertical pneumatic diffusivity and thickness of the unsaturated zone and the vertical hydraulic diffusivity and thickness of the saturated material above the aquifer cross spectral estimation is used to fit the response to atmospheric loading of three water wells to the theoretical curves in order to yield estimates of three of the key dimensionless parameters these estimates then are used to make estimates or place bounds on the vertical pneumatic diffusivity of the unsaturated zone the lateral permeability of the aquifer and the composite vertical hydraulic diffusivity of the overlying saturated materials

theory of dipole flow in uniform anisotropic aquifers a theory of dipole flow is developed to model flow induced by a vertical circulation well consisting of injection and extraction chambers in a single borehole included in the theory are an analytical description of the kinematic flow structure around a vertical circulation well and the drawdown in the well chambers using stokes stream function simple criteria are derived to determine the region of intensive recirculation this region extends from the dipole center approximately five distances between chamber centers in the radial direction and two distances between chamber centers in both vertical directions the vertical scale does not depend on anisotropy of hydraulic conductivity and the radial scale is corrected for anisotropic aquifers based on these estimates criteria are given for the selection of the appropriate aquifer model to employ in five settings including infinite semi infinite confined semi infinite unconfined finite confined and finite unconfined aquifers applications of dipole flow theory are given for analytical estimation of the capture zone for recirculation wells and for simultaneous measurement of horizontal and vertical hydraulic conductivity in uniform anisotropic aquifers using steady state measurements of drawdown in the well chambers

porosity from seismic data a geostatistical approach using a geostatistical technique called cokriging the areal distribution of porosity is estimated first in a numerically simulated reservoir model then in an oil bearing channel sand of alberta canada the cokriging method consistently integrates 3 d reflection seismic data with well measurements of the porosity and provides error qualified linear mean square estimates of this parameter in contrast to traditional seismically assisted porosity mapping techniques that treat the data as spatially independent observations the geostatistical approach uses spatial autocorrelation and crosscorrelation functions to model the lateral variations of the reservoir properties in the simulated model the experimental root mean square porosity error with cokriging is 50 percent smaller than the error in predictions relying on a least squares regression of porosity on seismically derived transit time in the reservoir interval in the alberta reservoir a cross validation study at the wells demonstrates that the co

integrating laboratory creep compaction data with numerical fault models a bayesian framework 1 we developed a robust bayesian inversion scheme to plan and analyze laboratory creep compaction experiments we chose a simple creep law that features the main parameters of interest when trying to identify rate controlling mechanisms from experimental data by integrating the chosen creep law or an approximation thereof one can use all the data either simultaneously or in overlapping subsets thus making more complete use of the experiment data and propagating statistical variations in the data through to the final rate constants despite the nonlinearity of the problem with this technique one can retrieve accurate estimates of both the stress exponent and the activation energy even when the porosity time series data are noisy whereas adding observation points and or experiments reduces the uncertainty on all parameters enlarging the range of temperature or effective stress significantly reduces the covariance between stress exponent and activation energy we apply this methodology to hydrothermal creep compaction data on quartz to obtain a quantitative semiempirical law for fault zone compaction in the interseismic period incorporating this law into a simple direct rupture model we find marginal distributions of the time to failure that are robust with respect to errors in the initial fault zone porosity

millennial scale storminess variability in the northeastern united states during the holocene epoch for the purpose of detecting the effects of human activities on climate change it is important to document natural change in past climate1 in this context it has proved particularly difficult to study the variability in the occurrence of extreme climate events such as storms with exceptional rainfall1 previous investigations have established storm chronologies using sediment cores from single lakes2 3 4 5 6 7 8 but such studies can be susceptible to local environmental bias here we date terrigenous inwash layers in cores from 13 lakes which show that the frequency of storm related floods in the northeastern united states has varied in regular cycles during the past 13 000 years 13 kyr with a characteristic period of about 3 kyr our data show four peaks in storminess during the past 14 kyr approximately 2 6 5 8 9 1 and 11 9 kyr ago this pattern is consistent with long term changes in the average sign of the arctic oscillation9 suggesting that modulation of this dominant atmospheric mode may account for a significant fraction of holocene climate variability in north america and europe

analysis of tide and offshore storm induced water table fluctuations for structural characterization of a coastal island aquifer analysis of water table fluctuations can provide important insight into the hydraulic properties and structure of a coastal aquifer system including the connectivity between the aquifer and ocean this study presents an improved approach for characterizing a permeable heterogeneous coastal aquifer system through analysis of the propagation of the tidal signal as well as offshore storm pulse signals through a coastal aquifer offshore storms produce high wave activity but are not necessarily linked to significant onshore precipitation in this study we focused on offshore storm events during which no onshore precipitation occurred extensive groundwater level data collected on a sand barrier island sable island ns canada show nonuniform discontinuous propagation of the tide and offshore storm pulse signals through the aquifer with isolated inland areas showing enhanced response to both oceanic forcing signals propagation analysis suggests that isolated inland water table fluctuations may be caused by localized leakage from a confined aquifer that is connected to the ocean offshore but within the wave setup zone two dimensional groundwater flow simulations were conducted to test the leaky confined unconfined aquifer conceptualization and to identify the effect of key parameters on tidal signal propagation in leaky confined unconfined coastal aquifers this study illustrates that analysis of offshore storm signal propagation in addition to tidal signal propagation provides a valuable and low resource approach for large scale characterization of permeable heterogeneous coastal aquifers such an approach is needed for the effective management of coastal environments where water resources are threatened by human activities and the changing climate

hypoaigic influences on groundwater flux to a seasonally saline river hypoaigic zones are aquifer volumes close to and beneath the shores of saline surface water bodies and are characterized by the presence of time dependent natural convection and chemical stratification when transient and cyclic processes are involved there is significant potential for complex flow and reaction in the near shore aquifer presenting a unique challenge to pollutant risk assessment methodologies this work considers the nature of some hypoaigic processes generated by the seasonally saline canning river of western australia near a site contaminated by petroleum hydrocarbons a dissolved hydrocarbon plume migrates within the shallow superficial aquifer to the nearby bank of the canning river beneath the river bank a zone of complex fluid mixing is established by seasonal and tidal influences understanding this complexity and the subsequent ramifications for local biogeochemical conditions is critical to inferring the potential for degradation of advecting contaminants a range of modelling approaches throws light on the overall topographic controls of discharge to the river on the saline convection processes operating under the river bank on the potential for fluid mixing and on the various important time scales in the system saline distributions simulated within the aquifer hypoaigic zone are in at least qualitative agreement with previous field measurements at the site and are strongly affected by seasonal influences groundwater seepage velocities at the shoreline are found to be positively correlated with river salinity calculations of fluid age distributions throughout the system show sensitivity to dispersivity values however maximum fluid ages under the river appear to be diffusion limited to a few decades the saline convection cell in the aquifer defines a zone of strong dispersive dilution of aged many decades deep aquifer fluids with relatively young several months riverine fluids seasonal recharge and river salinity cycles induce regular perturbations to the convection cell yielding intra annual variations of 50 in seepage velocity and almost 30 in wedge penetration distance at the plume location

reconstruction of ob river russia discharge from ring widths of floodplain trees crdf global research partnerships program ruc1 7075 ek 12 fscx 15 61824 0 russian foundation for basic research 13 04 01964 05 04 48298 00 05 65041

tidal fluctuations in a leaky confined aquifer localised effects of an overlying phreatic aquifer damping of tidal head fluctuations in a leaky confined coastal aquifer is enhanced by leakage into an overlying phreatic aquifer we show that the phreatic aquifer is however resistant to the leakage flow and in particular a deep phreatic aquifer can reduce the leakage effects significantly an analytical solution based on a vertical flow model for the phreatic aquifer is derived for quantifying the role of this upper free water body in tidal propagation in the lower semi confined aquifer

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

applicability of analytical solutions to tidal propagation in circular islands abstract the propagation of tides into coastal aquifers is an important phenomenon in the migration of coastal contaminants for the representation of shoreline boundary conditions in regional scale groundwater models and for the estimation of aquifer properties based on tidal amplitude attenuation and or phase increase in this study an analytical solution to the propagation of tidal fluctuations in a radial flow field applicable to circular islands is compared to the existing straight coastline ferris solution the analytical solution is compared to numerical simulation using seawat of a simple harmonic ocean tide and its propagation within a circular island this represents the first attempt to combine a previous correction that allows seawat to simulate axisymmetric flow and a modification to seawat to create tidal boundary conditions bench testing the analytical solution against the numerical model confirms the numerical approach the circular island solution is compared to the ferris solution in terms of tidal amplitude decay and phase shift whereas amplitude decay from the ferris solution is valid only for near shore locations within circular islands the ferris solution produces reasonable phase lag estimates for typical aquifer diffusivities and for most locations within circular islands by comparing the ferris and circular island solutions we propose a correction factor to the ferris solution that allows it to be applied in circular boundary settings this extends the application of the widely applied ferris solution to a broader range of situations

tracer advection by steady groundwater flow in a stratified aquifer the perfectly stratified aquifer has often been investigated as a simple tractable model for exploring new theoretical issues in subsurface hydrology adopting this approach we show that steady groundwater flows in the perfectly stratified aquifer are always confined to a set of nonintersecting permanent surfaces on which both streamlines and vorticity lines lie this foliation of the flow domain exists as well for steady groundwater flows in any isotropic spatially heterogeneous aquifer in the present model example it is a direct consequence of the existence of a stream function we then demonstrate that tracer plume advection by steady groundwater flow in a perfectly stratified aquifer is never ergodic regardless of the initial size of the tracer plume this nonergodicity which holds also for tracer advection in any isotropic spatially heterogeneous aquifer implies that stochastic theories of purely advective tracer plume movement err in assuming ergodic behavior to simplify probabilistic calculations of plume spatial concentration moments

the estimation of fluid flow properties from the response of water levels in wells to the combined atmospheric and earth tide forces the water level in an open well tapping a confined formation is influenced by natural forces including the solid earth tide set and atmospheric pressure variation apv the spectral method is used to analytically derive a model for well response to both random and periodic components of the combined set and apv forcings csa an inverse theory and algorithm are developed in order to provide improved results when using the model to estimate the hydraulic parameters associated with a given formation an examination of the response surface of the estimation criterion reveals a uniqueness problem in estimating storativity s since there is little correlation between the transmissivity t and s estimators a good estimate for t is still possible independent of having accurate knowledge of s an estimate of t is possible only if the data contain sufficient information so that the analysis occurs within an identifiability window the csa estimation methodology is compared to individual set and apv schemes the csa scheme gives the greatest probability that sufficient information is contained in a data record so that t is indeed identifiable the results of applications to synthetic data indicate that the csa scheme gives a t estimate with the most precision and also that it requires collecting fewer observations these results are discussed in light of practical considerations when designing data collection procedures

saltwater wedge variation in a non anthropogenic coastal karst aquifer influenced by a strong tidal range burren ireland summary spatial and temporal changes in saltwater wedges in coastal karst aquifers are still poorly understood largely due to complex mixing processes in these heterogeneous environments but also due to anthropogenic forcing such as pumping which commonly affect natural variations in wedges the purpose of this study was first to characterize the hydrodynamic functioning of a karst aquifer in an oceanic temperate climate with little anthropogenic pressure but strongly influenced by a high tidal range and second to evaluate the extent and movements of a saltwater wedge influenced by both the tide and the natural recharge of the aquifer variations in specific conductivity combined with water chemistry results from six boreholes and two lakes located in the bell harbour catchment western ireland enabled us to assess the extent of the intrusion of the saltwater wedge into the aquifer as a function of both karst recharge and tidal movements at high low and neap spring tidal cycles the marked spatial disparity of the saltwater wedge was analysed as a function of both the hydrodynamic and the structural properties of the karst aquifer results showed that the extent of the saltwater wedge depended not only on the intrinsic properties of the aquifer but also on the relative influence of the recharge and the tide on groundwater levels which have opposite effects recharge in the burren area throughout the year is large enough to prevent saltwater intruding more than about one kilometre from the shore a strong tidal amplitude seems to be the motor of sudden saltwater intrusion observed in the aquifer near the shore while the position of the groundwater level seems to influence the intensity of the salinity increase competition between recharge and the tide thus controls the seawater inputs hence explaining temporal and spatial changes in the saltwater wedge in this coastal karst aquifer

obtaining parsimonious hydraulic conductivity fields using head and transport observations a bayesian geostatistical parameter estimation approach 1 flow path delineation is a valuable tool for interpreting the subsurface hydrogeochemical environment different types of data such as groundwater flow and transport inform different aspects of hydrogeologic parameter values hydraulic conductivity in this case which in turn determine flow paths this work combines flow and transport information to estimate a unified set of hydrogeologic parameters using the bayesian geostatistical inverse approach parameter flexibility is allowed by using a highly parameterized approach with the level of complexity informed by the data despite the effort to adhere to the ideal of minimal a priori structure imposed on the problem extreme contrasts in parameters can result in the need to censor correlation across hydrostratigraphic bounding surfaces these partitions segregate parameters into facies associations with an iterative approach in which partitions are based on inspection of initial estimates flow path interpretation is progressively refined through the inclusion of more types of data head observations stable oxygen isotopes 18o 16o ratios and tritium are all used to progressively refine flow path delineation on an isthmus between two lakes in the trout lake watershed northern wisconsin united states despite allowing significant parameter freedom by estimating many distributed parameter values a smooth field is obtained