thermal energy storage in a confined aquifer second cycle during the first 6 month injection storage recovery cycle of the auburn university aquifer thermal energy storage project water pumped from an upper supply aquifer was heated to an average temperature of 55oc with an oil fired boiler and then injected into a lower storage aquifer injection and recovery temperatures flow rates and temperatures at six depths in 10 observation wells and hydraulic heads in seven wells were recorded twice daily the second cycle injection which was performed in a manner similar to the first began on september 23 1978 and continued until november 25 1978 when 58 010 m 3 of water had been pumped into the storage aquifer the major problem experienced during the first cycle a clogging injection well was reduced by regular backwashing this was done 8 times during injection and resulted in a 24 average injection rate increase compared to the first cycle a 63 day storage period ended on january 27 1979 and production of hot water began with an initial temperature of 54oc by march 23 this temperature had dropped to 33oc with 66 400 m 3 of water and 76 of the injected thermal energy recovered this compares to 66 recovery during the first cycle over the same drop in production temperature production of hot water continued until april 20 at which time 100 100 m 3 of water and 89 of the injected thermal energy was recovered at a final production temperature of 27 5 o c during the second cycle measurements were made of relative land subsidence and rebound to a precision approaching 0 1 mm the surface elevation near the injection well rose 4 mm during injection fell during storage and fell more rapidly toward its original elevation during production this movement was due to thermal expansion and contraction rather than to effects caused by head changes in the storage aquifer

reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk roberts helen plater a j 2007 reconstruction of holocene foreland progradation using optically stimulated luminescence osl dating an example from dungeness uk the holocene 17 4 pp 495 505 rae2008

a model for a moving interface in a layered coastal aquifer the framework of the present study is the development of a new approach to describe the displacement of fresh water by salt water in a layered coastal aquifer the aquifer is composed of horizontal layers possessing different hydraulic conductivities which are also different in the saltwater and the freshwater zones a one dimensional analysis is performed describing the displacement of the saltwater freshwater interface under the influence of freshwater flow toward the sea several analytical solutions are found revealing the effects of various parameters on the interface displacement process on the basis of these solutions several type curves for different freshwater saltwater hydraulic conductivity are drawn the model is calibrated by matching a type curve with field data taken from an observation well and is further used to predict the evolution of the interface shape and position

evaluation of single well injection withdrawal tests in swedish crystalline rock using the lagrangian travel time approach a series of 10 single well injection withdrawal swiw tests are evaluated with two tracers each uranine and cesium cs an evaluation tool for swiw tests in crystalline rock is presented on the

interpretation of field tracer tests of a single fracture using a transient solute storage model the results and interpretation of five induced gradient tracer tests performed at five different average interborehole fluid velocities in a single fracture in monzonitic gneiss are described the experiments were conducted using radioactive 82br and a fluorescent dye as conservative tracers where the tracers were pulse injected into radial convergent and injection withdrawal flow fields the flow fields were established between straddle packers isolating the fracture in three boreholes over distances of 12 7 29 8 m the tracer breakthrough curves were determined from samples of the withdrawn groundwater and were interpreted using residence time distribution rtd theory and two deterministic simulation models the rtd curves of the tracer experiments were interpreted by fitting to the field data a simple advection dispersion model and an advection dispersion model with transient solute storage in immobile fluid zones both models consider the different flow field geometries associated with injection withdrawal and radial convergent tests comparison of the fits obtained by the simulation models suggest that the initial period of solute transport in single fractures is advection dominated and with increasing tracer residence time or decreasing fluid velocity transport progresses toward more fickian like behavior during the advective dominated period the transient solute storage model is shown to adequately describe the asymmetries and long tails characteristic of the fracture rtds interpretation of the tracer experiments using both simulation models further suggests that induced gradient tracer experiments are likely to underestimate the dispersive characteristics of single fractures under natural flow conditions

an analytical solution for describing the transient temperature distribution in an aquifer thermal energy storage system a mathematical model is developed for predicting the temperature distribution in an aquifer thermal energy storage ates system which consists of a confined aquifer bounded from above and below by the rocks of different geological properties the main transfer processes of heat include the conduction and advection in the aquifer and the conduction in the rocks the semi analytical solution in dimensionless form for the model is developed by laplace transforms and its corresponding time domain solution is evaluated by the modified crump method field geothermal property data are used to simulate the temperature distribution in an ates system the results show that the heat transfer in the aquifer is fast and has a vast effect on the vicinity of the wellbore however the aquifer temperature decreases with increasing radial and vertical distances the temperature in the aquifer may be overestimated when ignoring the effect of thermal conductivity the temperature distribution in an ates system depends on the vertical thermal conduction in the rocks and the horizontal advection and thermal conduction in the aquifer the present solution is useful in designing and simulating the heat injection facility in the ates systems copyright 2010 john wiley sons ltd

borehole dilution tests in the vicinity of an extraction well abstract a mathematical solution is derived for a borehole dilution test conducted in the proximity of an extraction well under conditions where the theis assumptions are applicable the solution is similar to the steady state velocity case except for a factor that accounts for the transient response of the aquifer to pumping curves calculated from the derived solution show a delay in response that increases with the specific storage of the aquifer and with the radius from the extraction well the delay decreases with increasing values of hydraulic conductivity and aquifer thickness deviations of the response curves from the straight line steady state velocity case can be used to calculate the hydraulic diffusivity while the limiting slope at late time can be used to calculate groundwater flux when borehole dilution tests are conducted at several intervals over the thickness of the aquifer under steady state velocity conditions k z can in principle be calculated using several equations depending on the type of information available two existing methods to account for the distortion of the flow lines near the open test interval are related to well construction and development reasonable estimates of borehole factors can only be obtained for minimally developed wells

twin lake tracer tests setting methodology and hydraulic conductivity distribution following evaluation of three potential sites a fluvial sand aquifer with high 0 7 1 6 m d 1 linear average groundwater flow velocities was instrumented with a fully penetrating injection well and 82 monitoring installations over a 40 m flow path length two natural gradient tracer migration experiments have employed pulse injections of a nonreactive radioisotope 131i in a study of hydraulic conductivity structure and dispersive characteristics of the flow system the use of a gamma emitting radionuclide in these experiments allowed measurement of tracer distribution by scanning fully penetrating boreholes with a scintillation detector this technique provided many advantages in data collection over conventional tracers including unprecedented resolution of the vertical distribution of tracer measurements without pumping and the attendant concerns for flow system perturbation and minimal manpower for sample analysis tracer breakthroughs at monitors along the axis of flow revealed the presence of heterogeneities in aquifer hydraulic conductivity at two scales over the 40 m path length six regions with hydraulic conductivities substantially different from adjacent strata were identified thicknesses of these regions varied from 0 2 to more than 3 m their lateral extents in the direction of groundwater flow ranged from 15 m to more than 40 m smaller strata with an average thickness of 0 34 m and lengths of less than 10 m were detected within all six of the hydraulic conductivity regions but there was no evidence of increases in local dispersivity with increased transport distance as a result of these variations the six hydraulic conductivity regions do however have measurable effects on whole aquifer dispersion stratification characteristics of the tested aquifer believed to have been deposited in a sandy braided river are consistent with those observed in similar modern environments estimation of the magnitude and spatial structure of hydraulic conductivity variations in aquifers of concern would be greatly aided by studies of the stratification characteristics in well exposed modern or lithified sedimentary analogues

radiocarbon dated sediment sequences from the belgian coastal plain testing the hypothesis of fluctuating or smooth late holocene relative sea level rise the late holocene deposits of the coastal lowlands bordering the southern north sea were formed by a renewed expansion of the tidal environment replacing freshwater peats the sea level history during the last 2500 years inferred from the post peat deposits containing little to no datable organic material is characterized by two conflicting schools of thought the first one supports a smooth sea level curve the second approach underpins fluctuating sea level changes the fluctuating approach also uses facies variations recorded in the post peat deposits to provide a chronostratigraphical subdivision linked to transgressions and regressions this paper examines the controlling factors responsible for the facies variations in the post peat deposits in order to test the approach of the fluctuating sea level the results of sedimentological investigation coupled with radiocarbon dates of intertidal shells from four shallow outcrops located in nearby sand filled late holocene tidal channels in the belgian

seepage measurements from long lake indiana dunes national lakeshore long lake located near lake michigan within the dune complexes of indiana dunes national lakeshore usa was formed some time during the pleistocene and holocene epochs a surficial aquifer underlies long lake which is either a source or sink for the later the hydrologic processes in the lakeshore and surrounding environs have been significantly altered during the agricultural municipal and industrial development of the region limited data suggest that the organisms of long lake have elevated levels of several contaminants this study attempts to quantify seepage within the lake to assess the potential threat to groundwater quality seepage measurements and minipiezometric tests were used to determine seepage within the lake seepage measurements and minipiezometric tests suggest that water seeps out of long lake thus recharging the groundwater that flows southwest away from the lake there is a great deal of variability in the seepage rate with a mean of 11 5 10 4 11 2 10 4 m d 1 the mean seepage rate of 0 3 m yr 1 for long lake is greater than the 0 2 m yr 1 recharge rate estimated for the drainage basin area the long lake recharge volume of 2 5 105 m3 yr 1 is approximately 22 of the volume of the lake and is significant when compared to the total surface recharge volume of 4 8 105 m3 yr 1 to the upper aquifer of the drainage area there is a potential for contamination of the groundwater system through seepage from the lake from contaminants derived from aerial depositions

analysis and interpretation of single well tracer tests in stratified aquifers this study deals with the definition and measurement of the dispersive properties of a stratified aquifer based on the single well tracer test knowledge of such dispersive properties are of fundamental importance to the evaluation analysis and simulation of contaminant migration in groundwater a subject of great interest in recent years in the single well test tracer is pumped into the formation for a period of time and then pumped out concentration data are obtained from the injection withdrawal well and from one or more sampling observation wells which may be multilevel our analysis of such a test is based on a lagrangian eulerian numerical model which considers the depth dependent advection in the radial direction and local hydrodynamic dispersion in the vertical and radial directions results show that the movement of an injected tracer in a stratified aquifer may be accurately simulated without resorting to the use of a scale dependent full aquifer dispersivity if the flow field is known in sufficient detail when the advection process is simulated accurately the values of local dispersivity will be small constant and on the order of those measured in the field or laboratory at individual levels in the aquifer the full aquifer breakthrough curves measured in observation wells in a single well test in a stratified aquifer are determined by the hydraulic conductivity profile in the region between the injection withdrawal well and the observation well if the travel distance between these wells is typical of most test geometries however the relative concentration versus time data recorded at the injection withdrawal well during the withdrawal phase is primarily a measure of mixing in the aquifer due to local dispersion which has taken place during the experiment the amount of mixing will depend on both the hydraulic conductivity distribution in the aquifer and the size of the experiment as the experiment scale increases the effects of local vertical dispersion will become larger compared to the effects of local radial dispersion local vertical dispersion will cause a solute traveling in a high conductivity layer in an aquifer to migrate into adjacent low conductivity layers where its movement will be relatively slow in comparison in the initial design of a tracer test it is important to have some idea of the type of nonhomogeneity with which one is dealing more information of a broad nature concerning the types or classifications of nonhomogeneities that exist in natural aquifers would be very useful future research in this area is needed

analytical solutions to non fickian subsurface dispersion in uniform groundwater flow abstract analytical solutions are obtained by the fourier transform technique for the one two and three dimensional transport of a conservative solute injected instantaneously in a uniform groundwater flow these solutions account for dispersive non linearity caused by the heterogeneity of the hydraulic properties of aquifer systems and can be used as building blocks to construct solutions by convolution principle of superposition for source conditions other than slug injection the dispersivity is assumed to vary parabolically with time and is thus constant for the entire system at any given time two approaches for estimating time dependent dispersion parameters are developed for two dimensional plumes they both require minimal field tracer test data and therefore represent useful tools for assessing real world aquifer contamination sites the first approach requires mapped plume area measurements at two specific times after the tracer injection the second approach requires concentration versus time data from two sampling wells through which the plume passes detailed examples and comparisons with other procedures show that the methods presented herein are sufficiently accurate and easier to use than other available methods

geological modeling of submeter scale heterogeneity and its influence on tracer transport in a fluvial aquifer 1 we developed a new model of aquifer heterogeneity to analyze data from a single well injection withdrawal tracer test conducted at the macrodispersion experiment made site on the columbus air force base in mississippi usa the physical heterogeneity model is a hybrid that combines 3 d lithofacies to represent submeter scale highly connected channels within a background matrix based on a correlated multivariate gaussian hydraulic conductivity field the modeled aquifer architecture is informed by a variety of field data including geologic core sampling geostatistical properties of this hybrid heterogeneity model are consistent with the statistics of the hydraulic conductivity data set based on extensive borehole flowmeter testing at the made site the representation of detailed small scale geologic heterogeneity allows for explicit simulation of local preferential flow and slow advection processes that explain the complex tracer response from the injection withdrawal test based on the new heterogeneity model advective dispersive transport reproduces key characteristics of the observed tracer recovery curve including a delayed concentration peak and a low concentration tail importantly our results suggest that intrafacies heterogeneity is responsible for local scale mass transfer

an experimental and numerical study of evaporite mineral dissolution and density driven flow in porous media abstract subsurface mineral dissolution problems exhibit complex behaviors which are difficult to model and validate numerically controlled physically validated experimental problems can be used to better understand mineral dissolution and subsequent numerical representation bridging the gap between numerical models and field observations the objective of this work was to collect the first controlled physical measurements in a porous aquifer overlying an evaporite mineral and to create a numerical model of the system the problem studied was modified from the classic hydrocoin level 1 case 5 problem three flow gradients in a porous aquifer were investigated in duplicate in a 2 d box problem the duplicate measurements had high variability shown by numerical modeling to be a result of initial conditions variable flux representing dissolution sharp gradients and variable dispersivity the physical measurements of parameters and fields were important for calibration success the numerical models including sensitivity analyses were capable of simulating flow patterns observed concentrations and peaks resulting from observed initial conditions the numerical models were a key tool in understanding factors influencing the flow and spread of salt within the system the models were limited by the ability to detail physical observations difficult in both the laboratory and for potential field applications the results provided insight in the hydrocoin level 1 case 5 numerical simulations with flow appearing to be swept forward however observed concentrations were lower than commonly modeled

an analysis of dispersion in a stratified aquifer the dispersion of a conservative solute produced as a result of vertical variations of hydraulic conductivity in a horizontal stratified aquifer of finite thickness is analyzed by applying the moment method of aris to solve the governing advection dispersion equation describing mass transport in the analysis it is assumed that the aquifer is of constant thickness and of infinite lateral extent the hydraulic conductivity is a known function of the vertical coordinate only and the flow is unidirectional parallel to the stratification the applicable aris moment equations are developed in a suitable nondimensional form analytical solutions are obtained for the zeroth and first moments and for the time derivative of the second moment of the longitudinal concentration distribution for the case of an instantaneous plane source for several idealized hydraulic conductivity profiles parabolic linear step function and cosine profiles and their even periodic extensions the analysis gives the time dependent variation of the longitudinal macrodispersivity for these idealized cases throughout the transient development of the dispersion process the results of the analysis are applied to a field measured hydraulic conductivity profile and predicted values of the longitudinal macrodispersivity are compared with field results an important conclusion from the analyses is that nonuniformities in the hydraulic conductivity profile which persist over long distances may produce rather large values of longitudinal macrodispersivity which are comparable to those observed in some aquifers and which are much larger than those predicted by some previous stochastic analyses implications of the analytical results for field dispersion problems are discussed

significance and timing of the mid 17th century eruption of long island papua new guinea tibito tephra was first recorded in the central highlands of papua new guinea png in 1971 by the late 1970s the tephra had been mapped across tens of thousands of square kilometres traced to i

a multi level pore water sampler for permeable sediments abstract the construction and operation of a multi level piezometer multisampler designed to collect pore water from permeable sediments up to 230 cm below the sediment water interface is described multisamplers are constructed from 1 inch schedule 80 pvc pipe one quarter inch flexible pvc tubing leads from eight ports at variable depths to a 1 inch tee fitting at the top of the pvc pipe multisamplers are driven into the sediment using standard fence post drivers water is pumped from the pvc tubing with a peristaltic pump field tests in banana river lagoon florida demonstrate the utility of multisamplers these tests include collection of multiple samples from the permeable sediments and reveal mixing between shallow pore water and overlying lagoon water

the palaeoenvironments of kuk swamp from the beginnings of agriculture in the highlands of papua new guinea pollen phytolith and charcoal records from the archaeological wetland site of kuk swamp wahgi valley papua new guinea spanning the period from 20 000 to 270 cal bp are compiled to reconstruct past vegetation and plant exploitation during the earliest to late phases of agricultural development samples collected from exposed stratigraphic sections associated with archaeological excavations enable detailed reconstructions of local vegetation and fire histories that can be directly linked to archaeological evidence for agricultural activity the record of past environmental change is constructed through detailed chronological control and stratigraphic correlation across the swamp revealing evidence of early holocene vegetation disturbance including short term patchy forest loss and burning considered indicative of plant exploitation it is not until the mid holocene after 7000 cal bp that persistent and widespread forest loss occurs with burning and the transplanting of musa banana into an open grassland environment which is contemporary with local archaeological features representing cultivation practices multi proxy palaeoecological evidence at kuk provides a robust vegetation history and land use chronology for the upper wahgi valley for the late pleistocene and holocene including the emergence of an agricultural landscape by 7000 cal bp subsequent agricultural developments in the highlands of new guinea can be seen as a series of continuing indigenous innovations in agricultural technology in the face of increased land degradation climate change and external influences

reply to the comment on shoreface sand supply and mid to late holocene aeolian dune formation on the storm dominated macrotidal coast of the southern north sea by e j anthony m mrani alaoui and a hequette marine geology 276 2010 100 104 abstract baeteman and mauz 2012 raise three main points of disagreement with anthony et al 2010 regarding the probable age and mode of formation of an inland dune on the north sea coastal plain of france 1 the proposed chronology of dune formation 2 the interpretation of the stratigraphic data from the dune and 3 the proposed model of dune formation the chronology proposed as an alternative by baeteman and mauz 2012 is not based on radiometric ages directly derived from this inland dune baeteman and mauz 2012 propose a sea level driven mechanism of coastal evolution that fails to demonstrate how this dune was formed and they do not provide any evidence in support of what they refer to as a surge drift line involved in the formation of this dune nor of the mechanisms of dune formation we highlight numerous flaws in the comments and interpretations of baeteman and mauz 2012 that demonstrate failure to take into account recent findings on the main sediment transport mechanisms and morpho sedimentary outcomes characterising the shallow sediment rich mixed storm and tide dominated macrotidal shoreface of the southern north sea compounded by an inadequate understanding of morphodynamic processes and sediment supply conditions involved in coastal progradation

performance analysis and simulation of a two well tracer test at the mobile site during the late summer of 1984 a two well tracer test was performed which involved travel distances of 38 3 m to 90 m a bromide tracer slug was injected at one well while groundwater was simultaneously pumped from the other well the two well test which required 32 days to complete was then simulated by geotrans inc using a three dimensional advection dispersion model with a longitudinal dispersivity of 0 15 m a transverse dispersivity of 0 05 m and the permeability distribution being measured independently in a single well test single well test results which involved a travel distance of 5 5 m indicated that the hydraulic conductivity varied by about a factor of 4 throughout the aquifer thickness the two well test simulation made without knowledge of the test results and without any calibration was remarkably good local hydrodynamic dispersion was negligible so that the concentration versus time breakthrough at the withdrawal well could be simulated just as well with a quasi three dimensional advection model having zero hydrodynamic dispersion this implies that over the travel distances applicable to the two well test the spreading of the slug in the aquifer depended mainly on macroscopic velocity variations that were quantifiable in terms of the inferred permeability distribution this result which pertains to an aquifer in a fluvial terrace deposit of quaternary age is similar to that observed by pickens and grisak in a sandy glaciofluvial aquifer near the chalk river nuclear laboratories in canada such flow systems can result in fully three dimensional plumes with high concentrations of contaminant moving over large horizontal distances in the higher permeability zones

a late holocene palaeoecological record from ambra crater in the highlands of papua new guinea and implications for agricultural history a series of monoliths collected from ambra crater in the upper wahgi valley papua new guinea have been subject to multiproxy pollen microcharcoal and diatom palaeoecological investigation the palaeoecological record enables a relatively high resolution reconstruction from c 4000 500 cal bp throughout the sequence the valley floor and crater area were continuously deforested and carpeted with a grassland disturbance taxa mosaic vegetation communities in the valley were largely unaffected by successive tephra deposition events although some muted effects occurred tephra deposition did have considerable local effects on soil water conditions and hydrology in the base of the crater the ambra crater record is consistent with longer chronologies from wetlands in the upper wahgi valley which document extensive disturbance to dryland forests and their replacement with grasses and other disturbance taxa from the mid holocene the ambra crater record taken in conjunction with previously published multisite data enables critique and dis crimination of different interpretations of agricultural history in the highlands during the late holocene

temperature distribution around a well during thermal injection and a graphical technique for evaluating aquifer thermal properties analytical solutions of temperature distribution are developed for the problem of thermal injection into a confined aquifer with a caprock of finite thickness heat transfer by horizontal conduction and convection within the aquifer and by vertical conduction in the caprock and bedrock is considered steady state and two asymptotic unsteady state solutions of temperature distribution around a thermal injection well are determined one unsteady state solution is for short time periods and the other is for long time periods the caprock thickness is only important in the long time period solution a graphical technique is presented using hypothetical data for evaluationg four pertinent aquifer thermal properties 1 the horizontal thermal conductivity of the aquifer 2 the thermal capacity of the aquifer 3 the vertical thermal conductivity of the caprock and 4 the thermal capacity of the caprock field measurements of aquifer temperatures near the steady state condition are theoretically needed to utilize the graphical technique in many practical situations a long time period is required to achieve a steady state condition therefore a modified graphical technique employing an unsteady temperature distribution is illustrated and can be used to estimate the horizontal thermal conductivity and aquifer thermal capacity

twin lake tracer tests longitudinal dispersion two natural gradient dispersion tests were conducted at the chalk river nuclear laboratories ontario in 1982 and 1983 in order to quantify field scale dispersion processes over a 20 and 40 m distance of a radiotracer migration the patterns of dispersion that were observed in the field using a dry access tube monitoring technique were compared with patterns predicted by the advection dispersion model with constant parameters analysis of the time concentration profiles of the tracer at observation wells located along the mean direction of the longitudinal spreading showed that the dispersion model adequately describes the dispersion patterns actually observed and averaged over the aquifer depth the values of longitudinal dispersivity determined from continuous time concentration profiles were virtually equal to those obtained from laboratory scale columns the dispersive properties of the aquifer were characterized at the local scale by a constant independent of travel distance dispersivity value of 0 0045 m averaging the test data over the aquifer depth analogous to the information provided by a fully penetrating pumping well yielded a full aquifer dispersivity varying in an irregular fashion from 0 16 to 0 06 m the scale effect observed between local scale and full aquifer dispersivities is the result of inhomogeneity of the aquifer and the concentration averaging produced by the sampling instrumentation the results of two tracer tests also showed that the use of the dry access tube monitoring technique for field experimentation provides detailed representation of spatial and temporal distribution of a radiotracer s activity and consequently provides a practical means to determine the groundwater velocity field and dispersive properties of porous materials

how subsoil morphology and erodibility influence the origin and pattern of late holocene tidal channels case studies from the belgian coastal lowlands abstract this paper aims at a better understanding of the late holocene re entrance of the tidal system in the belgian coastal plain after a 2 3 ka years long period of peat growth the re entrance was associated with the development of deeply incised tidal channels the initial cause of the re entrance still a missing link in the understanding of the late holocene coastal change is investigated by focusing on the specific location of the young tidal channels the research though based in the western belgian coastal plain is relevant to the lowlands of the southern north sea and english channel the investigation combines stratigraphic radiocarbon and sedimentological data together with maps showing the morphology of the pre holocene surface the distribution of the holocene deposits and the erosional surface produced by the late holocene channels it appears that the young channels re occupied the same position as their early and mid holocene predecessors the re entrance of the tidal system began by a removing of the upper part of the older channels which originated from the mainland once the channels were cleaned of sediment tidal waters could re enter and rework the easily erodable sand of the older channels and pleistocene deposits

characterization of hydrogeologic properties for a multi layered alluvial aquifer using hydraulic and tracer tests and electrical resistivity survey a multi layered aquifer typical of riverbank alluvial deposits in korea was studied to determine the hydrologic properties the geologic logging showed that the subsurface of the study site was comprised of four distinctive hydrogeologic units silt sand highly weathered and fresh bedrock layers the electrical resistivity survey supplied information on lateral extension of hydrogeologic strata only partially identified by a limited number of the geologic loggings the laboratory column tracer test for the recovered core of the sand layer resulted in a hydraulic conductivity of 5 00 10 2 cm s the slug tests performed in the weathered rock layer yielded hydraulic conductivities of 4 32 7 72 10 4 cm s hydraulic conductivities for the sand layer calculated from the breakthrough curves of bromide ranged between 2 08 10 3 and 2 44 10 2 cm s with a geometric mean of 6 89 10 3 cm s which is 7 times smaller than that from the laboratory column experiment the trend of increasing hydraulic conductivity with an increase in tracer travel length is likely a result of the increased likelihood of encountering a high conductivity zone as more of the aquifer is tested the combined hydrogeologic site characterization using hydraulic tests tracer tests and column test with geologic loggings and geophysical survey greatly enhanced the understanding of the hydrologic properties of the multi layered alluvial aquifer

study of tracer movement through unsaturated sand abstract a column of 100 cm length and 15 4 cm diameter was filled with sand a solute displacement experiment using tritium as a tracer was conducted under saturated water flow conditions analysis of the observed effluent concentration resulted in an estimated dispersivity of 0 094 cm solute displacement experiments under unsaturated water flow conditions were conducted by leaching the column intermittently on a daily basis with constant amounts of water as soon as the amount drained from the column was equal to the daily input tritium was added to the infiltrating water for some period three such experiments were conducted with different amounts of water infiltrated daily these amounts were small enough for the water flow to remain unsaturated the parameters of the hydrodynamic dispersion equation were fitted to the observed effluent concentrations very large dispersion coefficients were obtained with a dispersivity of about 7 3 cm a possible explanation of this phenomenon is the presence of immobile water pockets during unsaturated flow for all experiments it was found that about 36 of the water in the unsaturated column could be considered as immobile the exchange of solute between the mobile and immobile phases explains very well the large dispersion observed in the experiments conducted under unsaturated conditions

lacustrine responses to tephra deposition examples from mexico one of the major problems with palaeoclimate investigations in volcanic regions is that tephra inputs to lakes can cause changes in proxies analogous to those of climate forcing we review the range of impacts thought to be associated with tephra deposition distinguishing between direct effects on lake ecosystems and indirect changes to catchment nutrient cycles to achieve better understanding of these complex responses we have used high resolution diatom analysis from around 17 tephra layers in three mexican lakes a positive response to the tephra inputs has been identified for over half of these layers the most common response was for diatom concentrations to increase after tephra deposition also in plankton dominated systems fragilaria spp replaced stephanodiscus spp and aulacoseira spp an increase in the supply of silica to the lakes through their catchments is probably the cause of the diatom changes in the lakes studied direct effects of the tephra inputs to these lakes can be excluded as they would not generate changes of sufficient longevity the impact of these tephras which lasted for several decades was insufficient to perturb the underlying long term climate forcing of these lake systems c 2004 elsevier ltd all rights reserved

is unique scaling of aquifer macrodispersivity supported by field data spreading of conservative solutes in groundwater due to aquifer heterogeneity is quantified by the macrodispersivity which was found to be scale dependent it increases with travel distance stabilizing eventually at a constant value however the question of its asymptotic behavior at very large scale is still a matter of debate it was surmised in the literature that macrodispersivity scales up following a unique scaling law attempts to define such a law were made by fitting a regression line in the log log representation of an ensemble of macrodispersivities from multiple experiments the functional relationships differ among the authors based on the choice of data our study revisits the data basis used for inferring unique scaling through a detailed analysis of literature marcodispersivities in addition values were collected from the most recent tracer tests reported in the literature we specified a system of criteria for reliability and reevaluated the reliability of the reported values the final collection of reliable estimates of macrodispersivity does not support a unique scaling law relationship on the contrary our results indicate that the field data can be explained as a collection of macrodispersivities of aquifers with varying degree of heterogeneity where each exhibits its own constant asymptotic value our investigation concludes that transport and particularly the macrodispersivity is formation specific and that modeling of transport cannot be relegated to a unique scaling law instead transport requires characterization of aquifer properties e g spatial distribution of hydraulic conductivity and the use of adequate models

determination of longitudinal dispersivity in an unconfined sandy aquifer study of the mobility of contaminants in an aquifer is an important issue for the proper remediation of contaminated groundwater determination of associated solute transport parameters therefore is essential for investigation of the extent to which groundwater can be contaminated this study aimed at determining solute transport parameters for an unconfined sandy aquifer at a laboratory scale through various tracer tests using a conservative solute as a tracer tracer tests consisted of both well tracer tests single and double wells and an aquifer tracer test using a plume capturing device such as time domain reflectometry tdr the results showed that longitudinal dispersivities estimated from the single and double well tracer tests were 2 2 cm and 13 5 cm for a travel distance of 9 3 cm and 13 5 cm from the injection point respectively these results agreed reasonably well with the results of the aquifer tracer test the solute transport parameters obtained at multiple points in the aquifer through the aquifer tracer test revealed that the dispersivity length was proportional to the travel distance by a factor of 0 3 which was moderately higher than the value of 0 1 given in the literature copyright 2002 john wiley sons ltd

simulating fluoride evolution in groundwater using a reactive multicomponent transient transport model application to a crystalline aquifer of southern india abstract overexploitation of crystalline aquifers in a semi arid climate leads to a degradation of water quality with the main processes responsible for the observed salt loads probably being irrigation return flow irf and a high evaporation rate the present study has focused on modelling the f accumulation caused by irf below rice paddy fields in the small endorheic maheshwaram watershed andhra pradesh southern india the transient simulation was performed with a 1d reactive transport phreeqc column and took into account irf evaporation kinetically controlled mineral dissolution precipitation ion adsorption on fe hydroxides and mixing with fresh groundwater the results revealed the role of cationic exchange capacity cec in ca na exchange and calcite precipitation both favouring a decrease of the ca 2 activity that prevents fluorite precipitation iron hydroxide precipitation offers a not inconsiderable adsorption capacity for f immobilization the principal sources of f are fluorapatite dissolution and to a lesser extent allanite and biotite dissolution anthropogenic sources of f such as fertilizers are probably very limited after simulating an entire dry season irrigation cycle 120 days the results are in good agreement with the observed overall increase of cl in the maheshwaram groundwater the model enables one to decipher the processes responsible for water resource degradation through progressive salinization it shows that f enrichment of the groundwater is likely to continue in the future if groundwater overexploitation is not controlled

the impeller meter for measuring aquifer permeability variations evaluation and comparison with other tests a knowledge of the variation of horizontal hydraulic conductivity with vertical position k z is important in understanding the transport and dispersive properties of aquifers using an impeller meter to measure the discharge distribution in a screened well while pumping at a constant rate is a promising technique for obtaining the k z function such an application is described herein and the resulting k z functions are compared with those obtained previously using tracer tests and multilevel slug tests impeller meter data were the most convenient to obtain and tracer data the most difficult the k z functions obtained by the three methods were not identical but quite similar overall this similarity between both borehole tests and the larger scale tracer test showed that nonstationary hydraulic conductivity trends in a stochastic hydrologic sense exist in the test aquifer the impeller meter method was better able to detect the higher k layers than was the multilevel slug approach overall the results suggest that a practical strategy for fitting impeller meter tracer or multilevel slug test data to a given aquifer is to use the selected testing procedure to obtain a dimensionless distribution and then a standard pumping test to measure combining both types of information enables dimensional values for k z to be calculated in low permeability aquifers or near the bottom of a test well the fluid velocity due to pumping may be below the stall velocity of an impeller thus there is a definite need for the commercial development of more sensitive flow measuring devices such as heat pulse flowmeters hess 1986 which will extend the resolution of this field method

a sensitivity analysis of 2d fed a model for seawater encroachment in leaky coastal aquifers abstract in a previous study a two dimensional finite element model for dispersion 2d fed was developed and verified for some previously published problems the model was applied to predict the shape of equiconcentration and equipotential lines in coastal aquifers in this paper the 2d fed model is used to study the effect of several parameters on the simulated dispersion zone and flow pattern in leaky coastal aquifers the aquifer thickness greatly affects the dispersion zone as well as the equipotential lines except for certain ranges the effects of isotropic and anisotropic permeability coefficients and anisotropic dispersivities are relatively small cyclic flow is found near the shore boundary in many cases selection of a proper mesh size especially near the seaside is found to be very important to avoid instability problems

the impact of aquifer heterogeneity on the performance of aquifer thermal energy storage 1 heterogeneity in hydraulic properties of the subsurface is not accounted for in current design calculations of aquifer thermal energy storage ates however the subsurface is heterogeneous and thus affects the heat distribution around ates wells in this paper the influence of heterogeneity on the performance of a doublet well system is quantified using stochastic heat transport modeling the results show that on average thermal recovery decreases with increasing heterogeneity expressed as the lognormal standard deviation of the hydraulic conductivity field around the doublet furthermore heterogeneity at the scale of a doublet ates system introduces an uncertainty in the amount of expected thermal interference between the warm and cold storage this results in an uncertainty in thermal recovery that also increases with heterogeneity and decreases with increasing distance between ates wells the uncertainty in thermal balance due to heterogeneity can reach values near 50 percent points in case of regional groundwater flow in excess of 200 m yr to account for heterogeneity whilst using homogeneous models an attempt was made to express the effect of heterogeneity by an apparent macrodispersivity as expected apparent macrodispersivity increases with increasing heterogeneity however it also depends on well to well distance and regional groundwater velocity again the uncertainty in thermal recovery is reflected in a range in the apparent macrodispersivity values considering the increasing density of ates systems we conclude that thermal interference limits the number of ates systems that can be implemented in a specific area and the uncertainty in the hydraulic conductivity field related to heterogeneity should be accounted for when optimizing well to well distances

palynomorph evidence for tropical climate stability in the gulf of papua papua new guinea over the latest marine transgression and highstand 14 500 years bp to today abstract three sediment cores mv 41 mv 46 and md 50 from the gulf of papua gop papua new guinea were analyzed to assess changes in climatic oceanographic and sedimentological conditions over the last 14 5 kyr palynomorphs which were isolated from sediment core samples were collected at approximately 0 5 m intervals using a strong acid and oxidant md 50 non oxidant mv 41 mv 46 procedure radiocarbon 14c stable isotope geochronology magnetic susceptibility stable isotope analysis md 50 only oxygen 18 18o and carbon 13 13c and clay mineral maturity analysis were also completed for each core palynological data indicate that climatic conditions at sea level have remained warm wet and stable for the past 14 5 kyr with sea surface temperatures in the gop above 14 c potential decreases in vegetative cover marked the younger dryas interval 12 5 11 5 kyr bp as indicated by reduced pollen and spore recovery the end of the latest marine transgression and the subsequent return to eustatic sea level highstand is clearly delineated by increases in marine palynomorph recovery and decreases in mangrove pollen at approximately 5 kyr bp an increase in seasonality and potential el nino southern oscillation variability is observed in md 50 s oxygen isotope results at 5 kyr bp this is not supported by the palynomorph record likely because of the sampling interval and dilution by tropical pollen flora which indicates stable climatic conditions throughout the last 14 5 kyr sediment transport pathways in the gop remained fairly constant throughout the time interval which is supported by the lack of major changes in palynomorph assemblage composition

modeling of a liquid phase geothermal doublet system at regina saskatchewan canada the paper describes a computer mathematical model used to analyze the nature of the subsurface temperature disturbance that results from extraction of hot liquid from a geothermal production well with concurrent injection of cooled tailings water in a nearby disposal well the model was designed specifically to determine at an early stage of development an appropriate well spacing for the sedimentary basin geothermal project at regina canada assumptions include an infinite horizontal confined aquifer with uniform thickness and a finely dispersed pore system the mathematical model is based on an energy balance equation that combines darcy s law fourier s law and the change in heat content of an element within the active zone of the aquifer the numerical model is developed by means of the integrated finite difference technique short computer run times are achieved through the use of symmetry an expanding grid system and the use of the theis solution investigation of model sensitivity shows the model to be sensitive to such factors as interwell distance pumping rates porosity and aquifer thickness but quite insensitive to hydraulic conductivity and storativity sample results are given for regin aquifers undergoing both continuous and seasonal pumping isotherm maps show that the temperature disturbance evolves with time from a cooled circular area around the injection well to a strongly noncircular pattern with a protrusion of cooled water extending toward the production well the model is used to predict time of thermal breakthrough for regina aquifers using different pumping rates and interwell distances temperature histories for continuous pumping show that after thermal breakthrough the produced water undergoes a slight decline of temperature over a considerable time span for the withdrawal of equal volumes of fluid the temperature disturbance around the disposal well is spread over a slightly larger area for the seasonal pumping case compared to continuous pumping the thermal front is broader for the seasonal case because of the longer period of elapsed time during which thermal conduction occurs for seasonal operations thermal breakthrough will occur after less water has been pumped and there is a more gradual decline in the temperature of the production well after thermal breakthrough

dispersion in unconsolidated aquatic sediments inert tracer breakthrough experiments were used to parameterize hydrodynamic dispersion in undisturbed cores of surface sediment from lacustrine estuarine and marine depositional environments the sediments studied cover wide ranges of composition porosity 46 to 83 mean grain size 10 5to 10 2 cm and sorting 0 48 1 26 as expected hydrodynamic dispersion depends on the average longitudinal fluid flow velocity through the sediment plug at linear flow velocities exceeding 10 4 cm s 1 mechanical dispersion exceeds diffusion in all sediment cores studied compared to the classical studies on dispersion in sand columns however peclet numbers based on particle size measurements do not provide a reliable guide for predicting the transition from molecular diffusion dominated to mechanical dispersion dominated flow regimes in the sediments it is believed that the influence of pore structure on dispersion is much larger than that of particle size and that the characteristic pore lengths in the finest highly porous sediments are orders of magnitude larger than the mean grain size aggregation microlaminations and a heterogeneous pore size distribution may all contribute to non ideal flow conditions in the sediments tailing of the breakthrough curve occurred occasionally in fine grain sediment signifying micro and macro scale dispersion and non ideal flow behavior experiments showing significant non ideal flow through the sediment plug were not used for calculation of hydrodynamic dispersion coefficient

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

shoreface sand supply and mid to late holocene aeolian dune formation on the storm dominated macrotidal coast of the southern north sea abstract although pulses of coastal dune development in the course of the holocene have been attributed to variations in the availability of sand to modulation of sand supply by sea level change and to changes in wind conditions identifying the processes driving such pulses has been rather elusive the shore deposits bordering the tide and storm wave dominated southern north sea evince complex mid to late holocene stratigraphy and sediment heterogeneity these deposits include a unique 7 km long 0 3 0 6 km wide and up to 7 m high aeolian sand unit the ghyvelde dune occurring astride the french belgian border in an apparently anomalous inland location the dune overlies and is surrounded by tidal sandy and muddy deposits incorporating freshwater peat data from four mechanical cores and eight auger holes and three radiocarbon ages and one osl age suggest that this inland dune was part of an ancestral north sea sand flat and mudflat environment confronting the dune stratigraphy with the prevailing tide and storm controlled dynamics of shoreline progradation in this area indicates that dune formation occurred under a pulse of abundant sand supply resulting from the attachment to a mid holocene north sea tidal flat shore of a shoreface tidal bank under repeated storms this mode of onshore sand supply generates extremely rapid progradation up to 1 km over a century of the sand flat shore the surface of which serves as a large aeolian fetch zone for active backshore dune accumulation while parts of this surface trap locally significant amounts of mud that are subsequently fossilised by aeolian sand the potential influence of sea level and storminess in modulating the timing of shoreface sand supply and late holocene coastal dune development in the southern north sea reported in studies from other areas remains to be established

fate of silicate minerals in a peat bog an investigation of silicate weathering in a minnesota mire indicates that quartz and aluminosilicates rapidly dissolve in anoxic organic rich neutral ph environments vertical profiles of ph dissolved silicon and major cations were obtained at a raised bog and a spring fen and compared profiles of readily extractable silicon diatom abundance ash mineralogy and silicate surface texture were determined from peat cores collected at each site in the bog normally a recharge mound dissolved silicon increases with depth as ph increases exceeding the background silicon concentration by a factor of two silicate grain surfaces including quartz are chemically etched at this location despite being in contact with pore water at neutral ph with dissolved silicon well above the equilibrium solubility of quartz the increasing silica concentrations at circum neutral ph are consistent with a system where silicate solubility is influenced by silica organic acid complexes silica organic acid complexes therefore may be the cause of the almost complete absence of diatoms in decomposed peat and contribute to the formation of silica depleted underclays commonly found beneath coal

a dimensionless parameter approach to the thermal behavior of an aquifer thermal energy storage system to predict the performance of an aquifer thermal energy storage system an understanding of the system s hydrothermal behavior is needed one possibility is to run a detailed numerical simulation of the system however for a single well system in which fluid flow is limited to steady radial flow a characterization scheme based on a set of four dimensionless parameter groups allows production temperatures and energy recovery factors to be read from graphs the assumption of radial fluid flow is valid when buoyancy flow can be neglected and a well is fully screened in a horizontal aquifer which is confined above and below by impermeable layers criteria for little buoyancy flow include a low permeability or vertically stratified aquifer a small temperature difference between injected and ambient water and short cycle length the basic energy transport equations for the aquifer confining layer system with steady radial fluid flow in the aquifer are nondimensionalized to derive the key parameter groups next a numerical model which calculates the heat transfer in the aquifer and confining layers for an injection storage production cycle is run for a range of values of these groups the calculated production temperatures and energy recovery factors are then presented graphically as a function of the parameter groups comparisons between results of field experiments and recovery factors read from the graphs show good agreement

holocene evolution of relative sea level and local mean high water spring tides in belgium a first assessment abstract holocene age depth data from the belgian coastal plain basal peat data particularly are assessed in terms of local water and tide levels basal peat formation was generally induced by sea level rise effects of local seepage were limited and significant river gradient effects were absent no relation was found between the timing of basal peat inception and substrate permeability in general edaphic moisture conditions were unfavourable for organic accumulation prior to sea level related rise of the groundwater table error envelopes for the minimum level of local mean high water spring tides and for upper and extreme lower relative mean sea level limits during the last 9400 solar years 8400 yrs b p are presented these indicate that the rate of relative sea level rise showed marked retardations at ca 7500 7000 yrs cal b p 6650 6100 yrs b p and ca 5500 5000 yrs cal b p 4400 yrs b p a eustatic explanation appears to be plausible particularly for the former prior to ca 4000 yrs cal b p ca 3600 yrs b p the relative sea level rise in belgium differs noticeably from that established for the western netherlands with both diverging progressively back in time this implies that considerable differential crustal movement occurred between the two areas in the early holocene

sr isotopic ratios trace mixing and dispersion in co2 push pull injection experiments at the co2crc otway research facility australia abstract analysis of 87sr 86sr ratios and modelling of formation water injection water and produced water compositions from the co2crc otway research facility in victoria australia are used to test tracer behaviour and response in push pull experiments such experiments are an essential pre requisite to understanding the controls imposed by reservoir heterogeneities on co2 dissolution rates which may be an important stabilising mechanism for geological carbon storage the experiments otway stage 2b extension in 2014 comprised two sequential tests in which 100 t of co2 saturated water was injected with combinations of sr and br or li and fluorescein tracers each injection being followed by two staged extractions of 10 t and a final extraction of 50 t all spaced at 10 day intervals analysis of the 87sr 86sr ratios of the produced fluids from the first injection spiked with srcl2 and nabr is consistent with sr behaving conservatively this contrasts with previous interpretations in which br was argued to have behaved conservatively while sr which dilutes three times as fast as br was thought to be lost to a mineral phase such sr loss cannot explain the evolution of 87sr 86sr ratios the analysis of 87sr 86sr ratios in the waters produced after the second injection episode spiked with licl and fluorescein tracers allows calculation of the fractions of the formation waters and the injection waters from both tests 1 and 2 the sr li and so4 tracers the later formed by oxidation of formation sulphide all indicate similar rates of dilution that is consistent with conservative behaviour the results of the two injection episodes with spaced extractions are compared with two subsequent push pull injections in which the produced waters spiked with methanol were extracted continuously these continuous extraction experiments exhibited significantly less dilution over the same range of produced to injected water volumes up to only 0 6 than the earlier experiments with spaced extractions this implies that some process related to the pauses in extraction enhances mixing of injected and formation waters achieving the objective of using push pull experiments to assess reservoir heterogeneities and co2 dissolution rates will require better assessment of the various tracers to establish which behave conservatively followed a proper understanding of the causes of the variations in mixing as fluids are extracted from the formations

analysis of solute transport in a divergent flow tracer test with scale dependent dispersion it has been known for many years that dispersivities increase with solute displacement distance in a subsurface the increase of dispersivities with solute travel distance results from significant variation in hydraulic properties of porous media and was identified in the literature as scale dependent dispersion in this study laplace transformed analytical solutions to advection dispersion equations in cylindrical coordinates are derived for interpreting a divergent flow tracer test with a constant dispersivity and with a linear scale dependent dispersivity breakthrough curves obtained using the scale dependent dispersivity model are compared to breakthrough curves obtained from the constant dispersivity model to illustrate the salient features of scale dependent dispersion in a divergent flow tracer test the analytical results reveal that the breakthrough curves at the specific location for the constant dispersivity model can produce the same shape as those from the scale dependent dispersivity model this correspondence in curve shape between these two models occurs when the local dispersivity at an observation well in the scale dependent dispersivity model is 1 3 times greater than the constant dispersivity in the constant dispersivity model to confirm this finding a set of previously reported data is interpreted using both the scale dependent dispersivity model and the constant dispersivity model to distinguish the differences in scale dependence of estimated dispersivity from these two models the analytical result reveals that previously reported dispersivity distance ratios from the constant dispersivity model should be revised by multiplying these values by a factor of 1 3 for the scale dependent dispersion model if the dispersion process is more accurately characterized by scale dependent dispersion copyright 2007 john wiley sons ltd

comments on shoreface sand supply and mid to late holocene aeolian dune formation on the storm dominated macrotidal coast of the southern north sea by e j anthony m mrani alaoui and a hequette marine geology 276 2010 100 104 abstract anthony et al 2010 published a recent paper in marine geology on the origin and chronology of an inland dune for which they presented an explanation for the regional pattern of mid to late holocene coastal development this explanation contradicts other data collected from this coastal area it is moreover in contrast to our current understanding of holocene coastal evolution of the southern north sea the data used by anthony et al 2010 includes a number of inconsistencies that led the authors to incorrect conclusions this discussion reports on our critical evaluation of data and reasoning in antony et al 2010 we propose an alternative model of coastal evolution which is in line with the current knowledge about mid to late holocene coastal evolution

holocene evolution of the coast of holland abstract the holocene evolution of the coast of holland was controlled by the complex interaction of such diverse parameters as wave and tidal climate the rate of sea level rise and the morphology of the pre transgressional surface the latter in combination with the rate of sea level rise mainly determines the location of sediments sources and sinks while the hydrodynamic parameters mainly determine the rate and direction of sediment transport in the early holocene the low sea level in the shallow southern north sea strongly affected wave climate and tidal regime however the barrier and back barrier sedimentary record since 5000 14c yrs b p gives us no reason to assume major changes in these parameters since then so we conclude that breaks in barrier development are due to variations in rate of sea level rise inl combination with the morphology of the pre transgressional surface the transformation from an open tide dominated to a closed wave dominated coast which occurred in the subboreal period and the concomitant change in barrier movement from transgressive to regressive around 5000 yrs b p are the main events in the development of the coast of holland up to the middle ages the morphology of the pre transgressional surface gives a shoreline in the late atlantic which consists of two protruding headlands separated by a large tidal basin the southern headland is the alluvial plain of the rhine and the meuse the northern headland constitutes the moraines of the texel high the tidal basin in between is connected to the north sea by a large number of inlets the rate of sea level rise at that time 1 m century outran the supply of sediment to the tidal basin after 6000 yrs b p the rate of sea level rise decreased gradually whereas the rate of sediment supply remained constant this led to a gradual decrease in the tidal prisms of the inlets as the tidal basin was filled in with sediment shortly before 5000 yrs b p the first channels silted up and closed the last tidal channel disappeared around 3300 yrs b p leaving two inlets along the coast which were both connected to the river rhine the closure of the first inlets occurred at the same time as the barrier began prograding because 1 the rate of sea level rise diminished considerably 2 not all the sand supplied by longshore and cross shore transport disappeared into the tidal basin but instead could be used for barrier progradation and 3 ebb tidal deltas of the closed inlets provided major sand sources the prograding barrier sequence enclosed between the two headlands roughly forms a closed system using the relationships between tidal prism cross sectional area of inlets and volume of the ebb tidal delta and the results of modelling of longshore transport along the subboreal coast under present day wave conditions a simple sand budget for the coast of holland is given which shows that a large part of the sand now stored in the barrier sequence was obtained by cross shore transport from the north sea

radiocarbon dating of pollen by accelerator mass spectrometry radiocarbon dating of bulk sediments has been the standard method for establishing chronologies in the studies of lake sediment cores which have contributed significantly to our knowledge of late quaternary paleo environments these bulk sediment dates are presumed to be direct ageindicators for the speciments e g pollen or macrofossils which are actually being studied however several recent studies have reinforced long standing apprehensions concerning this presumption in this study we demonstrate for the first time the radiocarbon dating of pollen concentrate samples by accelerator mass spectrometry the dates obtained by this method should provide more reliable radiocarbon chronologies for paleo environmental studies than have been obtainable by bulk sediment dating

sensible energy storage in aquifers 2 field experiments and comparison with theoretical results ten successive in situ experimental investigations of hot water storage by a single well and a pair of wells doublet were conducted in 1976 1977 at bonnaud jura in a confined aquifer 2 5 m thick the injected volumes ranged from 500 1700 m3 temperature profiles were measured daily in 12 boreholes distributed along two perpendicular axes within 13 m of the injection well individual temperatures were measured by ten thermistors placed in the caprock the results are discussed and used to calibrate two mathematical models an axisymmetric model allows the calibration of average values of the parameters while a three dimensional model is used to determine their spatial variation in the horizontal plane the latter model leads to the identification of a nonhomogeneous transmissibility field which fully accounts for both hydraulic and thermal contour curves the models which were matched against particular experiments proved accurate when simulating other periods evidence is given of the importance to the recovery ratio of thermal dispersion in the aquifer and of the water content of the caprock in a final section experimental results of single well storage at bonnaud campuget and auburn are compared with general type curves derived in the companion paper they prove to yield adequate predictions of water temperature during the production phases