identifying structure and function of karst aquifer system using multiple field methods in karst trough valley area south china the xiangxi river basin south china is a steep terrain that hosts an extensive karst aquifer system with rapid subsurface runoff the karst networks are best developed in cambrian carbonates along the nnw and nne directions congruent with the predominant orientations of fissures the permeability tensor surface features and flow channels tracer tests define a fast subsurface flow component with a maximum velocity of 240 1055 m h that discharges to multiple outlets at high water levels and a slow flow component with a velocity of 15 m h at low water levels a theoretical response model defined the response times of four karst springs as being only 5 and 8 h for hydrographs and conductivity curves respectively also a mean recession coefficient of 0 032 1 h for the fast flow component was determined by spring recession analysis a conceptual structural model of the karst aquifer system explains the multiple flow outlets at high groundwater levels and the extensive development of highly connected karst conduits in upper cambrian strata

adjustment of the electromagnetic field distorted by 3 d heterogeneities summary the 3 d adjustment distance of electromagnetic fields distorted by lateral contrasts of conductivity was studied with applications to conductivity anomalies occurring near coasts or islands investigations of the electrical conductivity structure of the mantle depend critically on whether the distortion of the electromagnetic data is caused by local or by remote contrasts of conductivity with the help of simple models it is shown that the actual adjustment distance of the electric field along the off strike direction to the conductivity contrast is a balance between an adjustment distance related to the galvanic coupling of the upper layer to the substratum and a distance describing the horizontal scale of the electric currents deviated by the contrast in conductivity it is shown that this adjustment distance cannot exceed the effective dimension of the conductivity contrast consequently published adjustment distances of several thousand kilometres are unlikely to exist as a result sea floor electromagnetic soundings carried out at large distances from coastlines are useful for probing the local conductivity structure of the oceanic mantle the 2 d interpretation of the electric field in the offshore direction at stations perturbed by the coastal effect has a high probability of bias because the field is affected by the combination of the 2 d galvanic coupling and the effect of the horizontal short cut by the closest conductive channels of the electric current flowing in the ocean

geomagnetic variation anomalies and deflection of telluric currents summary we show that most of the abnormal variations of the transient magnetic field have deflection and canalization of telluric currents as main sources in order to do so we develop a formalism which is valid in a limited frequency range which satisfies the following hypotheses a the thickness of the laterally inhomogeneous upper layer is small with respect to the penetration depth of the transient field b self induction of the heterogeneities of conductivity can be neglected theoretical results and observations performed at mid latitudes are in good agreement the main result we establish is that deviation and canalization of the current responsible for the transient abnormal field do not affect their temporal variations the study of temporal variations of the abnormal field thus provides us with information about the structure of the crust in the region where the deviated and canalized currents are induced

lake bottom magnetotellurics the study of the electrical conductivity structure of the lower crust and the upper mantle and midmantle promises to place important constraints on the thermobaric and compositional state of the earth s interior such work particularly for depths above approximately 400 km is best attempted by magnetotelluric sounding an effort frustrated by the almost complete absence of stable long period electric field measurements in this paper we propose that proven techniques developed for seafloor magnetotellurics be applied also to deep freshwater lakes the establishment of such long period electric and magnetic observatories in the thermally stable low noise lake bottom environment will yield new insights on the deep electrical structure beneath the continents a lake bottom long span electric field array was deployed in a deep freshwater lake adjacent to seattle washington a vector flux gate magnetometer was buried on the shore of the lake and magnetotelluric data of high quality were collected the analysis of the data described in this work clearly demonstrates the feasibility of establishing such lake bottom continental magnetotelluric observatories inversion of the data provides a view of structure beneath the site consistent with regional seismic and tectonic models

conceptual hydrogeological model of flow and transport of dissolved organic carbon in a small jura karst system summary this paper aims at characterizing infiltration and solute transport processes in a karst system during flood events in order to build a conceptual model of hydrogeological functioning the study site is the small karst system of fertans in the french jura soil cover rock matrix and a small spring were monitored to measure hydrological and hydrochemical parameters and particularly a continuous dissolved organic carbon doc signal which is a relevant environmental tracer of fast infiltration we used two combined approaches first from hydrodynamic and hydrochemical data we identified the system structure consistent with a dual porosity scheme and characterized the main processes occurring during flood events second on the basis of this scheme we built a new conceptual hydrogeological model coupled with doc transport to numerically validate the hydrological functioning this modelling approach is based on a rainfall discharge model to simulate spring flow solute transport is modelled using mixing equations including an empirical retardation factor as well as a first order solute decay the model was calibrated and validated on a set of nineteen flood events showing its performances in simulating spring hydrographs and delayed doc signals during flood events with various rainfall intensities we showed that the recharge area of the karst system varied largely with low and high groundwater periods which was attributed to the state of hydraulic connectivity in the unsaturated zone the soil cover appeared to play an important role of mixing and transfer for the recharge water the model simulated the contributions of pre event and event waters during flood events and allowed a better quantification of the available resource it showed in particular that total discharge of some flood events during low water periods is mainly composed of pre event water via piston flow type processes finally this study shows that the mixing model can simulate solute transport correctly taking into account degradation and retardation processes it highlights the need for a quantitative approach on hydrochemical studies of karst systems in order to understand them better

groundwater balance estimation in karst by using a conceptual rainfall runoff model summary a conceptual rainfall runoff model is proposed for the estimation of groundwater balance components including the influences of time variant catchment boundaries and intercatchment groundwater flows karst underground is considered as a lumped system that contains 1 soil cover 2 epikarst zone and 3 vadose and phreatic zones the soil cover receives an average rainfall in catchment as the input into the system the epikarst zone is composed of a production store and a routing store the production store contributes to the loss of water in process of evapotranspiration the routing store contributes to the retention of percolated water and the lateral distribution of groundwater recharge between internal runoff and diffuse infiltration the vadose and phreatic zones accumulate groundwater in fissures fractures and vertical shafts and produce the vadose seepage vadose flow and shaft flow components of the karst spring discharge the parameter estimation and calculation procedure assemble the moisture balance and the groundwater balance approaches the rainfall runoff model is divided in two sub models the sub model based on the moisture balance of soil cover and epikarst production store calculates effective rainfalls the sub model based on the groundwater balance of vadose and phreatic zone calculates groundwater recharges the difference between the effective rainfalls and the groundwater recharges represents the contribution of epikarst zone and non conservative and time variant components to the groundwater balance the proposed methodology is applied to the jadro spring located near the city of split in croatia the calculated groundwater balance shows that the jadro spring aquifer contains a significant storage capacity in the vadose and phreatic zones during the year the aquifer may accumulate up to 140 millions m 3 the variability of calculated catchment area is explained with the time variant catchment boundary dependent on groundwater levels and the intercatchment groundwater flows from neighboring catchments the average catchment area of 396 km 2 is estimated by using the average monthly effective rainfalls and the average monthly groundwater recharges

insights into saline intrusion and freshwater resources in coastal karstic aquifers using a lumped rainfall discharge salinity model the port miou brackish spring se france the aim of this study was to develop a conceptual model of saline intrusion within coastal karst aquifers by analyzing rainfall discharge salinity data and to assess freshwater resources using a lumped modeling approach in a first step we analyzed 4 years of data rainfall discharge and salinity times series of the port miou brackish submarine spring in south france 400 km2 a conceptual model of the aquifer was then designed to differentiate a deep brackish reservoir and a shallower fresh one salinity variations at the spring are assumed to be controlled mainly by dilution originating from the fresh water in the shallower reservoir in a second step a lumped modeling approach was developed based on the conceptual model to simulate discharge as well as salinity over time we proposed a reservoir model to take into account slow and fast components in the shallower part of the aquifer and a saline intrusion in the deeper one this rainfall discharge salinity model was calibrated and validated for two periods of 1 5 years at a daily time step and was also tested to reproduce a multi annual evolution of the available discharge and salinity time series good simulation results were obtained to reproduce water and mass budgets as well as discharge and salinity dynamics during several hydrological cycles the simultaneous modeling of hydrodynamics and quality data showed the robustness of the model in addition to its easy implementation our results led us to propose a new type of seawater mixing mechanism for brackish springs the dilution type in addition to the well known ventury suction and head balance types the application of the lumped model on the port miou brackish spring validated the hydrogeological processes deduced from experimental data given an initial quantification of the freshwater resources available in such complex brackish karstic aquifers

distortion of magnetotelluric sounding curves by three dimensional structures distortions of magnetotelluric fields caused by three dimensional 3 d structures can be severe and are not predictable using one dimensional or two dimensional modeling i used a 3 d modeling algorithm based upon an extension of a generalized thin sheet analysis due to ranganayaki and madden 1980 to examine field distortions in crustal environments three major physical mechanisms cause these distortions these mechanisms are resistive coupling between the electrical mantle and upper crust resistive coupling between conductive features within the upper crust and local induction of current loops within good conductors each mechanism produces different spatial and frequency effects upon the background field so identification of the dominant mechanism can be used as an interpretational aid i finally use this analysis to identify distortion mechanisms seen in magnetotelluric data from beowawe nevada to aid in an interpretation of that area

dissolved organic carbon of infiltration within the autogenic karst hydrosystem this work aims at using the dissolved organic carbon doc as a tracer of infiltration in karstic aquifers with only diffuse recharge regular measurements of doc have been carried out in three karstic systems located in south eastern france during an hydrogeological cycle considering that the doc is mainly located in the soil it might be used as a tracer of the infiltration the behavior of the tracer considerably varies between the high and low flow periods the low concentrations of doc occur when the flow is mainly due to a long residence time of the water in the saturated zone whereas the concentration of doc increases with the contribution of recent waters during the flood period so the doc can be used as a tracer of the infiltration a comparison between the magnesium and the doc allows to demonstrate the ability of using the doc as a tracer of the water residence time

rainfall runoff relations for karstic springs part i convolution and spectral analyses karstic basins contain large reserves of subsurface water in this paper three karstic systems located in the pyrenees mountains ariege france are studied long records of rainfall and discharge rates for these karstic springs are available sampled at different rates daily hourly and half hourly this study aims at illustrating and assessing the capabilities and limitations of linear black box methods for analysing rainfall runoff type relationships and reconstructing runoffs from rainfall rate data using such systems in this study precipitation and discharge rates are considered as two autocorrelated and cross correlated stochastic processes a linear and stationary rainfall runoff model is adopted which is used for identification and simulation purposes different versions are analysed including a model based on a convolution integral between the precipitation rate p and a transfer function h t which can be thought of as the unit impulse response of the system it is shown that this linear stochastic model i e the statistical version although accurate in some respects does not represent the hydraulic behaviour of the system very well during low flow episodes and floods it is also shown that the use of fourier analysis alone does not lead to a satisfactory reconstitution of observed runoff sequences for these reasons the use of non linear random process input output models based on volterra integral series is proposed and discussed

analytical 1d dual porosity equivalent solutions to 3d discrete single continuum models application to karstic spring hydrograph modelling abstract one dimensional analytical porosity weighted solutions of the dual porosity model are derived providing insights on how to relate exchange and storage coefficients to the volumetric density of the high permeability medium it is shown that porosity weighted storage and exchange coefficients are needed when handling highly heterogeneous systems such as karstic aquifers using equivalent dual porosity models the sensitivity of these coefficients is illustrated by means of numerical experiments with theoretical karst systems the presented 1d dual porosity analytical model is used to reproduce the hydraulic responses of reference 3d karst aquifers modelled by a discrete single continuum approach under various stress conditions simulation results show the relations between the dual porosity model coefficients and the structural features of the discrete single continuum model the calibration of the equivalent 1d analytical dual porosity model on reference hydraulic responses confirms the dependence of the exchange coefficient with the karstic network density the use of the analytical model could also point out some fundamental structural properties of the karstic network that rule the shape of the hydraulic responses such as density and connectivity

relative importance of the saturated and the unsaturated zones in the hydrogeological functioning of karst aquifers the case of alta cadena southern spain summary from analysis of the hydrodynamic and hydrochemical responses of karst springs it is possible to know the behaviour of the aquifers they drain this manuscript aims to contribute to the characterization of infiltration process and to determine the relative importance of the saturated zone and of the unsaturated zone in the hydrogeological functioning of carbonate aquifers using natural hydrochemical tracers thus chemical components together with temperature and electrical conductivity both punctual and continuous records have been monitored in three springs which drain alta cadena carbonate aquifer southern spain an evaluation of the percentage of the electrical conductivity frequency peaks determined for each of the three springs is linked to the chemical parameters that comprise the conductivity signal one of these springs responds rapidly to precipitation conduit flow system due to the existence of a high degree of karstification in the unsaturated zone and in the saturated zone both of which play a similar role in the functioning of the spring another spring responds to precipitation with small increases in water flow somewhat lagged because the aquifer has a low degree of karstification even in the unsaturated zone which seems to influence its functioning more strongly than does the saturated zone the third spring drains a sector of the aquifer with a moderately developed degree of karstification one that is intermediate between the other two in which both the unsaturated zone and the saturated zone participate in the functioning of the spring but with the latter zone having a stronger influence these three springs show different hydrogeological functioning although they are in similar geological and climatic contexts which show the heterogeneity of karst media and the importance of an adequate investigation for groundwater management and protection in karst areas

a step wise semi distributed simulation approach to characterize a karst aquifer and to support dam construction in a data scarce environment abstract karst systems provide significant volumes of drinking water for large parts of the world population due to chemical weathering karst systems are characterized by strong heterogeneity resulting in a complex flow and storage behaviour presently available karst modelling strategies account for the karstic heterogeneity but often a lack of data limits their applicability in data scarce regions in this study a step wise simulation approach with a semi distributed karst model is proposed to characterize a karst aquifer at a data scarce region in southwest iran and to evaluate the leakage potential related to a future dam construction project at a river that cuts through the aquifer observed groundwater level time series were applied to calibrate and validate the model in order to avoid over parameterization the karst aquifer was split into three sections down the hydraulic gradient at each section groundwater level observations were used to iteratively calibrate the model from the first to the last section a spatial split sample test and sensitivity analysis served to evaluate the prediction performance and the identifiability of the model parameters finally simple scenarios of the river infiltration into the aquifer were applied to evaluate the leakage potential of the aquifer for future dam constructions the spatial split sample test showed that the semi distributed model provided reliable predictions but prediction performance and parameter identifiability decreased from the first towards the last aquifer section most probably due to increased aquifer complexity and propagation of uncertainty from the up gradient model section using sensitivity analysis we also show that parameter sensitivities increase significantly if parameter estimation was applied simultaneously to all three aquifer subsections using the model to assess the leakage potential indicated that without further technical measures the all river flow would be able infiltrate into the aquifer and the dam would never be filled up completely

hydrochemical dynamics of toc and no3 contents as natural tracers of infiltration in karst aquifers analysis of total organic carbon toc and no3 contents in the water at six springs in the province of malaga southern spain sampled under different hydrologic conditions revealed two different hydrochemical behaviour patterns for these natural tracers of infiltration toc content increased during every recharge period following the rapid arrival of water infiltrating through the soil on the other hand no3 content only rose during the first flood episodes normally in autumn and fell during the winter and spring ones this difference is consequence of the distinctive biogeochemical kinetics of nitrogen with respect to organic carbon both in the soil and within the aquifer unlike the mineralisation undergone by toc from the surface to the spring the no3 ion remains in the aquifer almost unaffected due to the oxidizing conditions prevailing within the karst medium which do not allow its denitrification and favour its preservation within the saturated zone in non polluted aquifers toc and no3 have a common origin in the soil and can be used to determine infiltration processes and the hydrogeological functioning of karst aquifers their different hydrochemical evolution provides information about mineralization and degradation processes of organic matter within karst aquifers which can be used to validate the vulnerability to contamination in this type of medium

conceptualization and classification of groundwater surface water hydrodynamic interactions in karst watersheds case of the karst watershed of the coulazou river southern france summary over the last two decades groundwater systems and surface water bodies are being more and more considered as a same entity which constitutes a single resource within the hydrologic system understanding groundwater surface water gw sw interactions is necessary to effectively manage the water resources concepts methods of analysis and classifications of these hydrodynamic interactions have thus been developed mostly in case of porous aquifer today gw sw interactions are still often poorly understood in many watersheds particularly in the case of complex aquifers like karst aquifers this study focuses on the influence of groundwater on the genesis and propagation of surface floods in the case of a highly karstified watershed gw sw hydrodynamic interactions are analysed i at a local scale focussing on hydrodynamic interactions between the karst aquifer in the vicinity of the river and the river and ii at a larger scale focussing on hydrodynamic interactions between a karst spring and sinkholes in the riverbed hydrodynamic time series are described using the karst watershed of the coulazou river western montpellier france as a case study results are used to adapt gw sw classifications that are usually devoted to porous media in case of the studied karst aquifer it is shown that the initial groundwater level may be used to forecast the type of hydraulic connection between the river and the saturated zone during flood however initial water level in the karst aquifer does not give any information about the flow direction gaining or losing stream during a flood the latter is found to be also controlled by the limited discharge capacity of karst conduits a conceptual model of karst river interactions during flood is given with concepts that are derived from the analysis of the coulazou watershed but that can be easily applied to most of the karst watersheds

the coast effect in terms of deviated electric currents a numerical study abstract a numerical thin sheet model is used to study the coast effect and to determine the magnitude of the near surface part of the anomalous field theoretical induction arrows are computed for australia california japan and the british isles and compared with the observed arrows this comparison shows that the main part of the coast effect and in some cases the whole coast effect is due to the deviation of currents flowing in the ocean by the upper part of the resistive continents it is suggested that the term coast effect should refer to the anomalous field whose source is near surface the coast effect so defined behaves like a regional anomaly superimposed on other anomalous features of the transient geomagnetic field a numerical determination of the geometrical features of the coast effect allows consideration of its elimination this elimination is performed for california and japan a correlation between the resulting residual and heat flow data is apparent in both cases

etude du champ magnetique anormal d origine intralithospherique the separation of the anomalous magnetic field with respect to the depth of lateral contrasts of conductivity is discussed in this paper it is shown that for most geophysical cases this separation is very simply performed for periods greater than 1800 s the anomalous field of an intralithospheric source is the difference between the observed anomalous field and the one related to the lateral contrasts of conductivity in the superficial part of the crust mostly the coast effect electromagnetic data observed in california are analysed using this method an anomalous field of intralithospheric source is shown to exist the study of this field provides us with indications about lateral variations of the physical and chemical conditions in the lithosphere the obtained results are in good agreement with data drawn from other earth sciences finally we show that such results can be obtained in other tectonically active areas japan and peruvian andes

contribution of time tracers mg2 toc δ13ctdic no3 to understand the role of the unsaturated zone a case study karst aquifers in the doubs valley eastern france 1 time tracers no 3 a toc d 13 c tdic mg 2 have been used to define the hydrodynamic behavior of a karst system high values in no 3 a and toc reflect rapid infiltration and consequently a short residence time within the aquifer whereas enriched d 13 c tdic and high mg 2 are expected for old water 9 springs and 5 boreholes have been sampled during three field campaigns in the doubs valley karst aquifer low water flood and recession periods a clear differentiation can be highlighted between boreholes characterized by a long residence time and springs that show a rapid infiltration considering only the springs values it appears that toc and d 13 c tdic contents can easily be correlated to the sampling period we show then the contribution of the unsaturated zone to the discharge during the low water period and the existence of reserves that seem badly connected to the drainage network and that contribute poorly to the minimal flow

modelling precipitation streamflow processes in karst basin the case of the jordan river sources israel summary a system approach daily precipitation streamflow model was developed for both the base and the surface flow components of large scale karst basins long term streamflow data were separated to baseflow and surface flow using the recursive digital filter method which provides time series for model calibration the hydrological model for karst environment hymke includes attributes to large scale preferential flow that recharge the groundwater and solve the problem of uncorrelated baseflow and surface flow in a karst environment hymke was applied simultaneously to the three major tributaries of the upper catchment of the jordan river which originate in the karstic region of the hermon mountain northern israel it was verified by comparing the calculated surface flow and baseflow with the daily time series of the baseflow separation procedure and demonstrated good agreement of both the surface r2 0 6 and baseflow r2 0 77 components of each stream

modelling karst vadose zone hydrology and its relevance for paleoclimate reconstruction abstract understanding past climatic changes allows us to better understand how our planet will evolve in the future one important source of information on paleoclimate is the analysis of speleothems that develop in karst caves and conduits due to the dissolution and precipitation of calcite however there are many uncertainties in paleoclimatic reconstruction with speleothems one of them being hydrological variability up to now only few studies have considered the impact of hydrological variability on speleothem formation and composition this review paper will provide an introduction to hydrological processes that have the potential to affect speleothem composition and the hydrological modelling approaches that are able to account for them it presents the current state of knowledge on paleoclimatic reconstruction using speleothems and shows that many important flow and transport processes have not yet been included in the interpretation of these archives mostly due to a lack of field information to parametrize them possible directions of future research efforts therefore include a better exploration of karst vadose zone processes and new approaches to incorporate this information into simulation models finally we foresee the exciting advances in reconstructing paleohydrology using karst hydrology models combined with speleothem growth rate and geochemical composition to understand how past climate changes affected the hydrological cycle and water availability

gravity field mapping from satellite altimetry sea gravimetry and bathymetry in the eastern mediterranean summary using data from the eastern mediterranean it has been shown how different data types may improve the quality of a gravity field approximation and a detailed geoid has been computed for the area the following data types were available a bias adjusted satellite altimetry b sea gravimetry c bathymetry and heights and d the spherical harmonic coefficient set osu81 complete to degree 180 a comparison of the satellite altimetry with geoid heights computed from the osu81 coefficients with and without the additional use of gravity data revealed substantial errors due to unmodelled orbit tilts a trend analysis of the altimeter data showed a tilt of 0 0026 m km 1 in eastern direction and 0 0067 m km 1 in northern direction the standard deviation s d of observed altimeter values minus osu81 geoid heights decreased from 1 53 m to 1 07 m after a correction for the tilt least squares collocation was then used to predict subsets of the data types a and or b from subsets of the same data types the results given here are in terms of the s d of observed minus computed values using every third value of the corrected altimeter data for gravity prediction a s d of 17 mgal was found when gravity values spaced 10 apart were used to predict 1 gravity values in a grid with the same mesh width shifted 5 and 2 altimeter observations a s d of 10 mgal and 0 42 m respectively were found a combination of gravity and altimeter data made the first s d of 10 mgal decrease to 7 mgal showing the impact of combining the two data types the use of topographic information to smooth the locally strongly varying gravity field gave substantial improvements in the gravity values predicted from either altimeter observations or gravity data error estimates of geoid heights predicted in between the altimeter tracks showed that a 65 per cent improvement had been achieved

contribution of correlation and spectral analyses to the regional study of a large karst aquifer charente france the purpose of the study is to demonstrate that correlation and spectral analyses can contribute to the regional study of a large karst aquifer an example is presented for the la rochefoucauld karst aquifer charente france different types of spatially distributed time series provide valuable spatio temporal information for the karst aquifer the available time series consist of the spring flow rates the flow rates at different locations in sinking streams the piezometric levels the electrical conductivity and temperature of the water the atmospheric pressure and the precipitation the analysis of the flow rates at the springs shows that the aquifer empties very slowly and has a large storage capacity hydrodynamic links were established between three of the four rivers flowing on the aquifer and the springs the results also demonstrate the important spatial heterogeneity of the aquifer and indicate that the most rapid flow occurs in the northern part of the aquifer hourly piezometric and electrical conductivity time series indicate that the transmissivity of the aquifer varies when some conductive channels become desaturated during the low water period the delays between the distributed recharge and the piezometric level between the localized river input and the flow rates at the springs and between the electrical conductivities in rivers and the main spring provide information on the travel times in the aquifer the observation of earth tides and barometric effects indicate that this apparently unconfined aquifer has a confined behaviour

isotope hydrology and geochemical modeling new insights into the recharge processes and water rock interactions of a fissured carbonate aquifer gran sasso central italy the goal of this paper was to characterize the recharge process and water rock interactions in a regional homogeneous fractured carbonate aquifer in the mediterranean environment gran sasso central italy through isotope data 2h 18o and 13c dic collected between 2006 and 2010 samples were collected from the springs of the gran sasso aquifer and from the underground nuclear physics laboratories located within the aquifer additionally the hydrochemical data and the reference hydrogeological frameworks of previous studies have been used as a starting point for the geochemical modeling the gran sasso aquifer which is bounded by terrigenous and clastic units acting as aquitards accommodates a uniquely broad regional groundwater which feeds springs mainly at its border with high steady discharge in total these springs discharge of more than 18 m3 s at a local scale for the aquifer core and at a regional scale for the overall aquifer 2h 18o and 13c dic isotope data the geochemical inverse modeling through phreeqc and the 13c dic fractionation modeling through netpath 2 0 show the following 1 clear processes of evaporation and related isotope enrichment may be ruled out 2 groundwater flow is active and extends to the overall aquifer without clear signs of layering and partitioning 3 groundwater flowpaths radiate from the core toward the periphery 4 in l aquila plain gran sasso groundwater mixes with shallow quaternary water at a ratio of one half 5 the main geochemical processes are the dissolution of calcite and dolomite and in some cases ion exchange occurs mg2 and so42 release ca2 adsorption 6 in the less mineralized recharge groundwater the 13c dic value is influenced by the 13c dic value of rainfall while in more evolved groundwater the final 13c dic value is reached by fractionation during the flowpaths indicating a lengthy interaction with limestone

effects of three dimensional structure on magnetotelluric sounding curves significant errors may result when applying one dimensional 1 d or two dimensional 2 d interpretation methods to magnetotelluric mt data collected in three dimensional 3 d environments both depths and resistivities can be grossly incorrect if 1 d or 2 d methods are applied in a 3 d setting we present examples of mt sounding curves generated using a 3 d modeling program madden and park 1982 and illustrate some interpretation pitfalls if 3 d effects are not considered the 3 d effects discussed herein are attributed to a surface layer heterogeneity and can be readily identified in mt data from a well designed mt survey the mt survey must include stations chosen to yield information about regional structure alternatively carefull examination of a geologic map will help the intepreter estimate the regional effects present in the data

offshore emslab objectives experimental phase and early results abstract a large electromagnetic em experiment dedicated to the exploration of lithosphere and asthenosphere associated with a spreading oceanic plate over its various tectonic regimes from ridge accretion to subduction was carried out during the second half of 1985 over an area extending from the juan de fuca ridge eastward across the coastal zone the cascade area and beyond referred to by the acronym emslab for em sound of lithosphere and asthenosphere beneath the juan de fuca plate the experiment involved two principal arrays one on land the other on the adjacent seafloor we report here on the outcome of the oceanic portion of emslab named offshore emslab for convenience the offshore emslab array of seafloor instrumentation included 40 self contained and free recording units including magnetometers electrometers and other oceanographic devices the latter were intended to provide information on the em fields generated by the interaction of oceanic motions with the main earth s field so as 1 to decontaminate ionospheric signals prior to magnetotelluric interpretation and 2 to illustrate the beneficial contributions that em observations may provide to ocean studies the collected database is described and assessed and an early illustration of its information content is given

2 d or 3 d interpretation of conductivity anomalies example of the rhine graben conductivity anomaly summary evidence of a conductivity anomaly in the rhine graben was first given about 15 years ago and consequently led to the definition of various models of induction in the region for periods ranging from a few minutes to a few hours these models reflect two antagonistic ways of explaining the observed anomalous variations of the magnetic field direct induction in a two dimensional 2 d structure or static distortion of telluric currents by the resistive crystalline vosges france and schwarzwalde germany massifs we discuss the two approaches using a simple formalism in particular we show that the self induction related to the anomalous currents flowing in the rhine graben is negligible for periods larger than 1000 s and that even though the static distortion of telluric currents does account for the observed anomaly 2 d models can explain some of its features we also show how the channelled currents are induced in the large sedimentary basins surrounding the area under study an experimental verification of this result is given

modelling of the functioning of karst aquifers with a reservoir model application to fontaine de vaucluse south of france summary this work deals with a rainfall discharge model applied to a well known karst aquifer a new approach is developed in order to minimize the fitting parameters here some of the model parameters do not result from a simple fitting as it was the case with earlier models i e some of them were assessed from the hydrograph analysis the conceptual model of the functioning is based on a production function based on a simple calculation of effective rainfall and a transfer function consisting of two reservoirs a slow discharge reservoir transfers the low flow and a rapid discharge reservoir feeds the high flow the model has three fitted parameters plus one for its initialisation three parameters are deduced from the hydrograph analysis over the entire time series for example the recession coefficient of the slow discharge reservoir is determined from the hydrodynamic analysis of the recession mangin a 1975 contribution a l etude hydrodynamique des aquiferes karstiques 3eme partie constitution et fonctionnement des aquiferes karstiques annales de speleologie 30 1 210 124 this model was tested over a ten years period on the fontaine de vaucluse french karst system the first hydrological year is used for fitting the model the nine other cycles validate the modelling the good quality of the model is proved by the nash criterion of 92 3 on the validation period moreover the simulation results were validated by a statistical analysis of measured and simulated time series the model successfully simulates both the high and low flow at the same time also it estimates the water volumes available in the different parts of the aquifer and it proposes a management tool capable of predicting the evolution of the discharge in different climate conditions

a conceptual model for groundwater circulation using isotopes and geochemical tracers coupled with hydrodynamics a case study of the lez karst system france abstract geochemical and isotopic tracers 18o 2h 87sr 86sr and 13ctdic were used to constrain origins and chemical evolution of groundwater in a mediterranean karst system the lez spring is the main perennial outlet of this karst system and supplies the metropolitan area of montpellier southern france with drinking water groundwater samples were collected at the lez spring and surrounding springs and wells under different hydrodynamic conditions during two hydrological years from june 2008 until may 2010 the results show that multiple hydrological compartments interact through an important network of fractures and faults they notably reveal connections between the main jurassic limestone aquifer and the overlying cretaceous valanginian compartment and between the surface and deep levels of the karst system isotopic tracers provided information about atmospheric recharge origins lithological signatures and chemical evolution of waters long residence time groundwaters issued from deep layers have a triassic hydrochemical fingerprinting being enriched in 13ctdic and characterized by high concentrations in cl as well as high sr ca mg ca and 87sr 86sr ratios evidences suggest that these waters mix with waters from the lower layers of the main jurassic aquifer constitute an intermediate storage compartment prone to rise through piston flow mechanism a two end member hydrograph separation based on ec tds was used to determine the proportion of the deep compartment s contribution to the lez spring outflow on average over the study period the main aquifer compartment and the deep aquifer compartment are estimated to contribute 92 6 and 7 4 of groundwater flow at the lez spring respectively

simplified physically based models for free surface flow in karst systems abstract most karst aquifers are characterized as a dual flow system comprised of a highly conductive conduit network embedded in a low porosity matrix the conduits are hydraulically connected to the matrix and behave either as a drain or a source depending on the recharge conditions simplified physically based models are herein employed to simulate the spring outflow for such aquifer systems the processes consist of a free surface flow in the conduit that is interacting laterally with a laminar groundwater flow in the surrounding matrix the conduit is subject to a concentrated recharge at its upstream end while the groundwater aquifer is subject to a diffuse recharge over its contributing surface area the flow system is described by a coupled system of partial differential equations the conduit flow is approximated by the kinematic wave equation and the groundwater flow by the linearized boussinesq equation the governing equations are solved using the laplace transform method after an appropriate linearization of the nonlinear coefficient the derived spring discharge models are a function of three dimensionless parameters the time lag parameter the lumped conduit parameter and the aquifer parameter the simulation results highlight the contrast between pressure driven and gravity driven flows and the importance of the conduit matrix interaction on the response of the karst system application of the models on real karst aquifers demonstrates their effectiveness in simulating the observed spring hydrograph using lumped physical parameters of the karst system

a four component mixing model for water in a karst terrain in south central indiana usa using solute concentration and stable isotopes as tracers the study area lies in a highly karstified carbonate terrain in south central indiana sinkholes conduits and caves form large secondary pathways for the subsurface flow as a result the discharge from a main emergence point for the subsurface flow system the orangeville rise quickly responds to the storm events and shows wide variations in flow rate water chemistry and stable isotopic compositions these responses are attributed to the mixing of water in secondary pathways in the study area recharge occurs through the thick mantled karst plain and the sinkhole plains and the role of soil layer and epikarst in the recharge process is of great importance rain dic 2 hco3 mg l 13cdic 7 soil water dic 544 hco3 mg l 13cdic 14 7 epikarstic water dic 224 hco3 mg l 13cdic 13 6 and phreatic diffuse flow water dic 299 hco3 mg l 13cdic 11 8 generally showed unique and constant dissolved inorganic carbon dic and 13cdic values over time using dic and 13cdic as tracers a four component mixing model was established for the karstic flow system by constructing the discharge hydrograph separation curves the mixing ratio of each component rain 10 6 soil 3 1 epikarstic 52 3 and phreatic 34 0 water was determined for the orangeville rise discharge over the testing period of 104 h after the storm event of 10 4 90 vadose water occupied 55 4 of spring discharge and this demonstrates the importance of the unsaturated zone especially the epikarst in the karstic flow systems

gravity empirical covariance values for the continental united states variances and correlation distances have been determined for terrain corrected bouguer anomalies in all 30 30 arc min blocks covering the continental united states also linear trend values were subtracted from the data in order to make the determination independent of the frequently irregular local data distribution gravity values predicted in a regular grid were used the prediction was made using least squares collocation constructing local surfaces representing the gravity anomalies for each 30 30 arc min block for this purpose 544 000 terrain corrected bouguer anomalies were available in the u s national geodetic survey gravity data base therefore in order to limit the computational effort a sequence of surfaces was determined by selecting in each block an increasing number of data points until a limit of the absolute value of the error equal to 4 mgal was reached this procedure reduced the number of gravity observations used per block to a very few in areas of little gravity variation to maximally 188 the correlation distance was found to be smallest in areas of high topography large variances are associated with the midcontinental gravity high and tectonic features on the pacific coast

identification of a karst system s intrinsic hydrodynamic parameters upscaling from single springs to the whole aquifer for water management purposes information about an entire aquifer system is generally more important than information about a specific spring since a karstic aquifer system might drain to several outlets conclusions derived from a single spring can be misleading for characterization and modeling in this study we apply a conceptual model to an alpine dolomite karst system in austria the particular challenge was that several small springs with strongly varying hydrological behavior and diffuse flow into surrounding streams drain this system instead of applying the model to a single spring it was calibrated simultaneously to several observations within the system aiming to identify the karst system s intrinsic hydrodynamic parameters parameter identification is supported by modeling the transport of water isotopes 18o the parameters were transferred to the whole system with a simple upscaling procedure and a sensitivity analysis was performed to unfold influence of isotopic information on parameter sensitivity and simulation uncertainty the results show that it is possible to identify system intrinsic parameters but the sensitivity analysis revealed that some are hardly identifiable only by considering uncertainty reasonable predictions can be provided for the whole system including isotopic information increases the sensitivity of some intrinsic parameters but it goes along with a sensitivity decrease for others however a possible reduction of prediction uncertainty by isotopic information is compensated by deficiencies in the transport modeling routines

quantification of temporal distribution of recharge in karst systems from spring hydrographs the estimation of the temporal distribution of recharge in karst aquifers is a challenge due to large heterogeneities in geometric and hydraulic parameters of the vadose and phreatic zone this article provides a time continuous approach for the estimation of inflow into the conduit system of a karst aquifer which consists of the sum of direct recharge and flow from the fissured matrix blocks into the conduit system the approach employs the first time derivative of the spring hydrograph and the recession coefficient of the conduit system for the determination of this function the first time derivative of the hydrograph describes the rate of change in spring discharge it reflects the ratio of inflow to and outflow from the conduit system the recession coefficient depends on the hydraulic diffusivity which controls the velocity of the signal transmission through the system as shown in parameter studies with a simplified serial two reservoir model direct recharge into the conduit system clearly dominates the early hydrograph response during recharge events even if the fraction of direct recharge represents just a few percent of total recharge this behaviour is caused by a large contrast in recession coefficients between conduit system and fissured matrix blocks the direct recharge component can therefore be separated from the estimated total inflow into the conduit system estimation of inflow into the conduit system of the gallusquelle spring swabian alb germany after a storm event yields similar results as those obtained from parameter studies the separation of the direct recharge component is in agreement with information from an independent isotope study the methodology has been further applied to a recharge event initiated by snowmelt as a result of daily variations of the air temperature a clearly diurnal cycle of inflow into the conduit system is estimated that is not easily recognizable from the spring hydrograph the applicability of the proposed methodology requires knowledge about the magnitude of the recession coefficient of the conduit system the characteristics of the conduit system become also apparent in the rapid transport of tracers the recession coefficient of the conduit system can for example directly be estimated from the reciprocal of the mean tracer travel time however for this type of analysis only tracer experiments covering the extent of the catchment should be taken into account for the gallusquelle catchment the recession coefficient obtained from the tracer experiment corresponds to that obtained from hydrograph recession analysis the estimated inflow into the conduit system and interpretation of temporal distribution of recharge is therefore based on a plausible and physically based parameter