karst water control and management in the hanxing mining area of north china the hanxing mining area of north china includes three coalfields fengfeng handan and xingtai six or seven coal seams can be commercially mined in permo carboniferous strata among which the lower three accounting for 37 of the total reserves are threatened with karst water from the underlain ordovician limestone hundreds of water inrush accidents have occurred and over 30 mines have been flooded resulting in heavy economic losses and casualties in order to avoid water inrushes and keep the mines safely operational dewatering in the karst aquifer was considered an essential measure unfortunately this practice has caused serious environmental problems such as surface subsidence sinkhole dry spring and water supply shortage on the basis of a series of investigations and tests in the last 20 years an alternative method mining with water pressure has been proposed and is the main focus of this paper by using this method the karst water in the limestone can be preserved to some extent and the coals can be mined in a relatively safe way

spatially integrated geodetic glacier mass balance and its uncertainty based on geostatistical analysis application to the western svartisen ice cap norway estimates of glacier mass balance using geodetic methods can differ significantly from estimates using direct glaciological field based measurements to determine if such differences are real or methodological there is a need to improve uncertainty estimates in both methods in this paper we focus on the uncertainty of geodetic methods and describe a geostatistical technique that takes into account the spatial correlation of the elevation differences when calculating spatially averaged elevation changes we apply this method to the western svartisen ice cap norway using elevation differences from the surrounding bedrock derived from stereophotogrammetry we show that the uncertainty is not only dependent on the standard error of the individual elevation differences but is also dependent on the size of the averaging area and the scale of the spatial correlation to assess if the geostatistical analysis made over bedrock is applicable to glacier surfaces we use concurrent photogrammetrical and laser scanning data from bedrock and a range of glacier surfaces to evaluate the dependency of the geostatistical analysis on the surface type the estimated geodetic mass balance and its uncertainty is 2 6 0 9 m w e for the period 1968 85 and 2 0 2 2 m w e for 1985 2002

correlation of porosity and permeability of reservoirs with well oscillations induced by earth tides summary periodic gravity perturbations known as earth tides produce minute expansions and contractions of subsurface geologic formations the motions induce water level oscillations in wells connected to the deep reservoirs and a measurable phase lag occurs between the maximum gravity and the maximum water level the amplitude of the water level oscillations induced by the small harmonic gravity variations of the earth tides and the phase lag relative to the tide are related to the reservoir porosity and permeability the motions of an elastic subsurface reservoir are analysed by considering an axially symmetric system of finite volume which is activated by oscillations of a rigid rock mass overlying the reservoir the geometric parameters involved are the thickness of the reservoir radial extent depth and fluid level in the well the physical parameters for which data are available or satisfactory estimates can be made are the fluid viscosity densities temperature compressibilities and shear modulus these properties refer to in situ conditions at large overburden pressure permeability and porosity at in situ conditions are not directly measurable and methods of indirect estimation are of practical interest this analysis correlates these two parameters with the amplitude and phase lag of the induced well fluid oscillation for the very small strains and fluid volume fraction changes induced by the tides slow flow of a viscous fluid through an isotropic porous matrix is assumed an axially symmetric analysis for a uniform permeable layer perturbed by the oscillations of the rigid overburden rock yields explicit expressions for the oscillation amplitude and phase in the well selected results from numerical solutions having a wide range of realistic parameter values are presented the results clearly show the dependence of amplitude and phase lag on the dimensionless permeability and the near proportionality of the amplitude on the reciprocal of the porosity porosity has no other significant influence finally it is shown how asymptotic approximations of the direct solution allow an inversion which determines the permeability and porosity in terms of the amplitude and phase lag given the other reservoir properties

modeling flow in phreatic and epiphreatic karst conduits in the holloch cave muotatal switzerland the holloch cave is a site where the hydrodynamic behavior of a karst conduit network can be observed with a high degree of precision observed heads discharge rates conduit sizes and conduit lengths have been compiled into a simple hydrodynamic model in order to check their consistency it was possible to calibrate and satisfactorily fit the observed data model results show the following 1 flow models which are able to simulate turbulent flow in variably saturated conduit networks can adequately model conduit flow dominated karst systems 2 karst systems may be strongly nonlinear especially because of the presence of epiphreatic conduits 3 under certain circumstances storage in the epiphreatic conduits and in the fissured limestone matrix can be neglected 4 the typical effective hydraulic conductivity of karst conduits ranges between 1 and 10 m s 1 and the louis formula is adequate to calculate head losses in those conduits 5 indirect measurements of flow velocity using scallop size indicate values of 30 40 of the maximal annual discharge and velocity derived from pebble size indicates values of 150 of the maximal annual discharge

contribution of icelandic ice caps to sea level rise trends and variability since the little ice age 1 in total icelandic ice caps contain 3600 km3 of ice which if melted would raise sea level by 1 cm here we present an overview of mass changes of icelandic ice masses since the end of the 19th century they have both gained and lost mass during this period changes in ice volume have been estimated both through surface mass balance measurements performed annually since 1990 and differencing of digital elevation models derived from various satellite and airborne observations while the glaciers showed little mass loss as the 20th century began losses increased rapidly after 1925 peaked in the 1930s and 1940s and remained significant until the 1960s after being near zero or even positive during the 1980s and early 1990s glacier mass budgets declined considerably and have since the mid 1990s shown an average annual loss of 9 5 1 5 gt a 1 contributing 0 03 mm a 1 to sea level rise since 1995 interannual variability in mass loss is high ranging from 2 7 to 25 3 1 5 gt a 1 corresponding to surface mass balances of 0 2 to 2 2 0 15 m we a 1 this variability is driven by climate fluctuations and also by transient reduction of albedo due to volcanic eruptions

transient hydraulic tomography in a fractured dolostone laboratory rock block experiments 1 the accurate characterization of fractured geologic medium imaging of fracture patterns and their connectivity have been a challenge for decades recently hydraulic tomography has been proposed as a new method for imaging the hydraulic conductivity k and specific storage ss distributions of fractured geologic media while encouraging results have been obtained in the field the method has not been rigorously assessed in a controlled laboratory setting in this study we assess the performance of transient hydraulic tomography tht in a fractured dolomitic rock block the block is characterized through flow through tests and multiple pumping tests the pumping test data were then analyzed with the tht code of zhu and yeh 2005 to image the fracture patterns and their connectivity through the delineation of k and ss distributions or tomograms results show that the tht analysis of pumping tests yields high k and low ss zones that capture the fracture pattern and their connectivity quite well and those patterns become more vivid as additional pumping test data are added to the inverse model the performance of the estimated k and ss tomograms are then assessed by 1 comparing the tomograms obtained from synthetic to real data 2 comparing the tomograms from two different pumping configurations 3 comparing the estimated geometric mean of the hydraulic conductivity kg from the k tomogram to the effective hydraulic conductivity keff estimated from the flow through tests and 4 predicting five independent pumping tests not used in the construction of the k and ss tomograms the performance assessment of the k and ss tomograms reveals that tht is able to image high k and low ss zones that correspond to fracture locations in the fractured rock block and that the tomograms can be used to predict drawdowns from pumping tests not used in the construction of the tomograms with reasonable fidelity

frequency dependence of the groundwater discharge at an artesian well as recognized from tidal fluctuation records groundwater discharge temperature and electrical conductivity of an artesian well were measured at nishiawakura okayama prefecture southwest japan the discharge ranged from 2 10 4 to 5 10 4 m3 s and showed tidal fluctuations of about 5 10 5 m3 s induced by strain although the groundwater temperature reflected the same tidal fluctuations as the discharge the electrical conductivity did not manifest tidal fluctuations the discharge slightly leads the theoretical tidal strain and its response to the strain of the diurnal constituents is different from that of the semidiurnal constituents the discharge fluctuations induced by atmospheric loading also have some frequency dependence these can be explained by the vertical or horizontal groundwater flow leakage from the aquifer which has been used in the explanation of the well water level fluctuations induced by tidal strain and atmospheric loading

river stage tomography a new approach for characterizing groundwater basins received 19 june 2008 revised 16 february 2009 accepted 12 march 2009 published 9 may 2009 1 data from tomographic surveys make an inverse problem better posed in comparison to the data from a single excitation source a tomographic survey provides different coverages and perspectives of subsurface heterogeneity nonfully redundant information of the subsurface fusion of these pieces of information expands and enhances the capability of a conventional survey provides cross validation of inverse solutions and constrains inherently ill posed field scale inverse problems basin scale tomography requires energy sources of great strengths spatially and temporally varying natural stimuli are ideal energy sources for this purpose in this study we explore the possibility of using river stage variations for basin scale subsurface tomographic surveys specifically we use numerical models to simulate groundwater level changes in response to temporal and spatial variations of the river stage in a hypothetical groundwater basin we then exploit the relation between temporal and spatial variations of well hydrographs and river stage to image subsurface heterogeneity of the basin results of the numerical exercises are encouraging and provide insights into the proposed river stage tomography using naturally recurrent stimuli such as river stage variations for characterizing groundwater basins could be the future of geohydrology however it calls for implementation of sensor networks that provide long term and spatially distributed monitoring of excitation as well as response signals on the land surface and in the subsurface

hydraulic tests in highly permeable aquifers 1 a semianalytical solution is presented for a mathematical model describing the flow of groundwater in response to a slug or pumping test in a highly permeable confined aquifer this solution which is appropriate for wells of any degree of penetration and incorporates inertial mechanisms at both the test and observation wells can be used to gain new insights into hydraulic tests in highly permeable settings the oscillatory character of slug and pumping induced responses will vary considerably across a site even in an essentially homogeneous formation when wells of different radii depths and screen lengths are used thus variations in the oscillatory character of responses do not necessarily indicate variations in hydraulic conductivity k existing models for slug tests in partially penetrating wells in high k aquifers neglect the storage properties of the media that assumption however appears reasonable for a wide range of common conditions unlike in less permeable formations drawdown at an observation well in a high k aquifer will be affected by head losses in the pumping well those losses which affect the form of the pumping induced oscillations can be difficult to characterize thus analyses of observation well drawdown should utilize data from the period after the oscillations have dissipated whenever possible although inertial mechanisms can have a large impact on early time drawdown that impact decreases rapidly with duration of pumping and distance to the observation well conventional methods that do not consider inertial mechanisms should therefore be viable options for the analysis of drawdown data at moderate to large times

geometry changes on svalbard glaciers mass balance or dynamic response the geometry of glaciers is affected by both the mass balance and the dynamics we present repeated gps measurements of longitudinal altitude profiles on three glaciers in svalbard and show that surface altitude changes alone cannot be used to assess the mass balance the three measured glaciers are in different dynamic modes and the observed changes in geometry are strongly affected by the dynamics nordenskioldbreen shows no significant change in the geometry indicating that the mass balance is in steady state with the dynamics on amundsenisen the surface has lowered by 1 5 2 0 m a 1 in the lower part of the accumulation area at 520 550 m a s l indicating that the ice flux is higher than the mass balance input probably due to a surge advance of the glacier further downstream affecting the higher part of the drainage area on kongsvegen the opposite situation was found here the geometry of the profile showed a clear build up of 0 5 m a 1 in the accumulation area and a lowering of 1 m a 1 in the lower part of the ablation area the ice velocity is very low giving a negligible vertical velocity component and an ice flux that is far smaller than the mass balance flux indicating that the glacier is building up towards a surge advance our results show that if mapping of height changes is to be used to monitor the response of the glaciers to climate change both surface net mass balance data and dynamic data are needed

influence of aquifer heterogeneity and return flow on pumping test data interpretation abstract analytical solutions of drawdown in unconfined aquifers are widely applied for determining the specific yield s y and the horizontal and the vertical hydraulic conductivity k r and k z respectively in many previous studies estimates of s y and k z were observed to be highly variable and physically unrealistic this has been attributed to the conceptualization of flow above the declining water table and aquifer heterogeneity in the applied models we present the analysis of time drawdown data from a pumping test instrumented with depth differentiated observation piezometers arranged in clusters applying homogeneous anisotropic aquifer models in combination with nonlinear least squares parameter identification techniques the data were analyzed in different groups analysis of data from individual piezometer clusters and simultaneous analysis of the entire data set from all piezometer clusters global analysis from the cluster analyses estimates of s y and k z exhibit large variances and depart from a priori estimates inferred from the hydrostratigraphy parameter estimates from the global analysis do not fall within the parameter bounds minimum and maximum values defined by the cluster analyses while heterogeneity appears to be the important reason for large parameter variances we discuss the influence of rarely considered aquifer return flow on drawdown and the inconsistent results from the cluster and global analyses we corroborate our findings with data on hydraulic gradients slug test data and results from the application of a more realistic numerical flow model

modelling the hydrologic functions of a karst aquifer under active water management the lez spring a rainfall discharge model is applied to an aquifer characterized by active groundwater management the lez karst aquifer in the south of france groundwater is withdrawn by pumping in the main drain 400 m upstream from the main spring and 48 m below the aquifer overflow level a reservoir model was developed to characterize the functioning of this aquifer it is based on a conceptual model of the karst aquifer that takes into account flow through both the saturated zone and the unsaturated infiltration zone both rapid and slow flow in the infiltration zone and flow in the saturated zone are modelled since pumping withdraws groundwater from the main drain of the saturated zone modules characterizing various pumping practices are taken into account in the saturated zone reservoir the model simultaneously simulates spring discharge and water levels in the drain which characterize the saturated zone of the karst the groundwater reserves stored in the saturated zone can then be estimated the model can be used for water management since runoff and overflow from the aquifer feeding the lez river depend on the degree of saturation of the aquifer the model could be used for the flood management

characterization of the hydrogeological experimental site of poitiers france by stochastic well testing analysis summary we assess the applicability and performance of the stochastic well testing methodology of neuman et al neuman s p guadagnini a riva m 2004 type curve estimation of statistical heterogeneity water resources research 40 w04201 doi 10 1029 2003wr002405 neuman s p blattstein a riva m tartakovsky d m guadagnini a ptak t 2007 type curve interpretation of late time pumping test data in randomly heterogeneous aquifers water resources research 43 w10421 doi 10 1029 2007wr005871 to provide a geostatistical characterization of the transmissivity distribution of a heterogeneous aquifer we use cross hole pumping test information also referred to as interference testing collected during two extensive and detailed experimental campaigns performed in 2004 and 2005 in a limestone aquifer constituting the hydrogeological experimental site hes of poitiers france the methodology we use is based on stochastic type curves of mean drawdown and associated variance and is aimed at revisiting the results of routine pumping tests within a stochastic framework it allows estimating the geometric mean integral scale and variance of local log transmissivities on the basis of quasi steady state head data when a randomly heterogeneous confined aquifer is pumped at a constant rate the results are discussed by comparison against a previous deterministic analyses performed at the site using the same dataset and b information obtained by geostatistical analysis of existing geophysical data the estimated values of integral scales and variance of log transmissivity are viewed in light of multiscale theories which conceptualize the heterogeneity of porous and fractured systems as hierarchical random processes distributed across a multiplicity of scales the scale dependence observed for the estimated variogram parameters of log transmissivity at the hes site is consistent with the behavior of published worldwide data

cross borehole slug test analysis in a fractured limestone aquifer summary this work proposes new semi analytical solutions for the interpretation of cross borehole slug tests in fractured media our model is an extension of a previous work by barker barker j a 1988 a generalized radial flow model for hydraulic tests in fractured rock water resources research 24 10 1796 1804 butler jr j j zhan x 2004 hydraulic tests in highly permeable aquifers water resources research 40 w12402 doi 10 1029 2003 wr002998 it includes inertial effects at both test and observation wells and a fractional flow dimension in the aquifer the model has five fitting parameters flow dimension n hydraulic conductivity k specific storage coefficient ss and effective lengths of test well le and of observation well leo the results of a sensitivity analysis show that the most sensitive parameter is the flow dimension n the model sensitivity to other parameters may be ranked as follows k le leo ss the sensitivity to aquifer storage remains one or two orders of magnitude lower than that to other parameters the model has been coupled to an automatic inversion algorithm for facilitating the interpretation of real field data this inversion algorithm is based on a gauss newton optimization procedure conditioned by re scaled sensitivities it has been used to interpret successfully cross borehole slug test data from the hydrogeological experimental site hes of poitiers france consisting of fractured and karstic limestones hes data provide flow dimension values ranging between 1 6 and 2 5 and hydraulic conductivity values ranging between 4 4 10 5 and 7 7 10 4 m s 1 these values are consistent with previous interpretations of single well slug tests the results of the sensitivity analysis are confirmed by calculations of relative errors on parameter estimates which show that accuracy on n and k is below 20 and that on ss is about one order of magnitude the k values interpreted from cross borehole slug tests are one order of magnitude higher than those previously interpreted from interference pumping tests these findings suggest that cross borehole slug tests focus on preferential flowpath networks made by fractures and karstic channels i e the head perturbation induced by a slug test propagates only through those flowpaths with the lowest hydraulic resistance as a result cross borehole slug tests are expected to identify the hydrodynamic properties of karstic channels and fracture flowpaths and may be considered as complementary to pumping tests which more likely provide bulk properties of the whole fracture karstic channel matrix system

a continuum representation of fracture networks part i method and basic test cases abstract a method to represent fracture networks as grid cell conductivities in a continuum model is described and evaluated the method is developed for a sparsely fractured rock with a conductivity field that is dominated by major fractures and fracture zones for such a fracture system it is believed that an accurate description of the correlation and anisotropy structure is essential the proposed method will capture these features of the fracture system the basic approach of the method is to evaluate accurate cell conductivity values for a staggered grid arrangement i e velocities are stored at cell walls and scalars at cell centres the balance of forces i e the darcy law is evaluated for a control volume centred around the point where the velocity component is stored fractures are assumed to have a thickness and conductivity the conductivity of a velocity control volume is calculated from the intersecting volume between the fracture and the velocity control volume intersecting volumes with their respective conductivities are added up to form the control volume conductivity the general conclusion is that the method results in accurate simulations it is expected that the method can be utilised in many practical groundwater simulations this statement is based on the results from three test cases with analytical solution and one test case where results are compared with those from established theories

self consistency of a heterogeneous continuum porous medium representation of a fractured medium a possible approach to representing fractured rocks is to use heterogeneous continuum porous medium cpm models in which each grid block has an effective permeability appropriate to represent the network of fractures within the block it needs to be demonstrated that the approach is self consistent that is the effective permeability on a length scale larger than the grid blocks derived using the heterogeneous cpm model is close to that derived directly from the underlying network model for models based on the borrowdale volcanic group at sellafield in the united kingdom and the granite at aspo in sweden it is shown that the use of heterogeneous cpm models is self consistent both for models using effective permeabilities determined directly from the underlying network of discrete features model and for models based only on the correlation structure of the effective permeability on the length scale of the grid blocks

the relative importance of head flux and prior information in hydraulic tomography analysis using cross correlation analysis we demonstrate that flux measurements at observation locations during hydraulic tomography ht surveys carry nonredundant information about heterogeneity that are complementary to head measurements at the same locations we then hypothesize that a joint interpretation of head and flux data even when the same observation network as head has been used can enhance the resolution of ht estimates subsequently we use numerical experiments to test this hypothesis and investigate the impact of flux conditioning and prior information such as correlation lengths and initial mean models i e uniform mean or distributed means on the ht estimates of a nonstationary layered medium we find that the addition of flux conditioning to ht analysis improves the estimates in all of the prior models tested while prior information on geologic structures could be useful its influence on the estimates reduces as more nonredundant data i e flux are used in the ht analysis lastly recommendations for conducting ht surveys and analysis are presented

aquifer heterogeneity characterization with oscillatory pumping sensitivity analysis and imaging potential 1 periodic pumping tests in which a fluid is extracted during half a period then reinjected have been used historically to estimate effective aquifer properties in this work we suggest a modified approach to periodic pumping test analysis in which one uses several periodic pumping signals of different frequencies as stimulation and responses are analyzed through inverse modeling using a steady periodic model formulation we refer to this strategy as multifrequency oscillatory hydraulic imaging oscillating pumping tests have several advantages that have been noted including no net water extraction during testing and robust signal measurement through signal processing through numerical experiments we demonstrate additional distinct advantages that multifrequency stimulations have including 1 drastically reduced computational cost through use of a steady periodic numerical model and 2 full utilization of the aquifer heterogeneity information provided by responses at different frequencies we first perform fully transient numerical modeling for heterogeneous aquifers and show that equivalent results are obtained using a faster steady periodic heterogeneous numerical model of the wave phasor the sensitivities of observed signal response to aquifer heterogeneities are derived using an adjoint state based approach which shows that different frequency stimulations provide complementary information finally we present an example 2 d application in which sinusoidal signals at multiple frequencies are used as a data source and are inverted to obtain estimates of aquifer heterogeneity these analyses show the different heterogeneity information that can be obtained from different stimulation frequencies and that data from several sinusoidal pumping tests can be rapidly inverted using the steady periodic framework

groundwater flow modeling of two levels perched karstic leaking aquifers as a tool for estimating recharge and hydraulic parameters summary perched springs in nature emerge from aquifers laying on aquitards within the unsaturated zone some of which emerge one above the other a finite element model was introduced using the feflow code for simulating the groundwater flow regime in each of these aquifers for quantifying the fraction of rain that recharges the aquifers and for estimating the hydrogeological parameters of the aquifers and aquitards many of the perched springs in israel are found in the judea group aquifer a stratified carbonate rock unit characterised by a well developed karst system the batir and jamia springs exemplifies such a system where batir is the upper spring discharging at the contact between aminadav and moza formations and jamia is the lower one discharging at the contact between kesalon and sorek formations the 25 year long measured spring s hydrographs were used to calibrate the spring s coefficients the hydraulic conductivities of the different layers the karst features and the yearly amount of rain recharging the spring

improving dual porosity medium approaches to account for karstic flow in a fractured limestone application to the automatic inversion of hydraulic interference tests hydrogeological experimental site hes poitiers france a reassessment improvement of a previous work by the authors is proposed on the inversion of hydraulic interference testing by means of dual porosity medium approaches the tests have been performed over a fractured limestone aquifer poitiers france showing a preferential and rapid flow path along open karstic drains all drawdown curves are merged together both in amplitude and time irrespective of their location relative to the single pumped well and classical dual porosity medium approaches are unable to mimic this behavior a pressure wave propagation by advection is added to the classical diffusion equations of dual porosity medium in order to stress the medium almost evenly whatever the distance from the pumped well the problem is set up to keep the continuous dual porosity medium framework with only two state variables i e the heads in fractures and matrix even though the wave velocity is not well conditioned because the ratio of the volume of drains to the total volume of the medium is unknown automatic inversion remains feasible the dual porosity medium without the drains can be homogeneous or fractal having in the latter case hydraulic parameters ruled by scaling power laws in both cases it is shown that adding an advection term allows to invert accurately all experimental drawdown curves statistical fluctuations of the sought hydraulic parameters are quite small and do not show any trend with respect to the distance thus modifying a dual porosity medium approach by adding an advection term allows for the homogenization of a reservoir that combines the general drainage of a fracture matrix system and a rapid drainage through karstic conduits

periodic pumping tests summary we performed pumping tests with a periodic succession of injection and production intervals in a field of three shallow boreholes penetrating a jointed sandstone formation tests were conducted at periods ranging from 10 to 5400 s and pumping rates between 5 and 20 l min 1 two types of analysis for the periodic pumping tests are presented injectivity analysis rests on the determination of the amplitude ratio and phase shift between the periodic flow rate and pressure records from the pumping well interference analysis is based on an evaluation of attenuation and phase shift between the periodic pressure signals at the pumping and monitoring wells a periodic excitation permits to employ standard signal processing tools such as fast fourier transformation facilitating the evaluation of weak signals the observed amplitude ratio and phase shift values are compared to analytical predictions of 1 d and radial flow models results of interference tests are particularly diagnostic for the applicability of a subsurface model our test results do not fully agree with any of the considered analytical models suggesting a heterogeneous subsurface we suppose that the two analysis methods yield averaged hydraulic properties of different volumes of a heterogeneous subsurface periodic injectivity tests screen the subsurface to increasing penetration depth if pumping period is systematically increased while the subsurface volume between pumping and monitoring well dominates the outcome of an interference test at all periods periodic pumping provides several operational advantages compared to conventional testing such as drawdown pulse or shut in tests periodic testing can be superposed on a long term operation reducing operational conflicts and permitting continuous monitoring of changes in subsurface properties processing of periodic signals provides results even in a field with strong transient changes in fluid pressure related for example to operations in nearby wells periodic pumping can be performed in a closed loop minimizing the total fluid volume involved

validation of hydraulic tomography in an unconfined aquifer a controlled sandbox study in this study we demonstrate the effectiveness of hydraulic tomography ht that considers variably saturated flow processes in mapping the heterogeneity of both the saturated and unsaturated zones in a laboratory unconfined aquifer the successive linear estimator sle developed by mao et al 2013c for interpreting ht in unconfined aquifers is utilized to obtain tomograms of hydraulic conductivity k specific storage ss and the unsaturated zone parameters pore size parameter and saturated water content s for the gardner russo s model the estimated tomograms are first evaluated by visually comparing them with stratigraphy visible in the sandbox results reveal that the ht analysis is able to accurately capture the location and extent of heterogeneity including high and low k layers within the saturated and unsaturated zones as well as reasonable distribution patterns of and s for the gardner russo s model we then validate the estimated tomograms through predictions of drawdown responses of pumping tests not used during the inverse modeling effort the strong agreement between simulated and observed drawdown curves obtained by pressure transducers and tensiometers demonstrates the robust performance of ht that considers variably saturated flow processes in unconfined aquifers and the unsaturated zone above it in addition compared to the case using the homogeneous assumption ht results as expected yield significantly better predictions of drawdowns in both the saturated and unsaturated zones this comparison further substantiates the unbiased and minimal variance of ht analysis with the sle algorithm

identifying fracture zone geometry using simulated annealing and hydraulic connection data a new approach is presented to condition geostatistical simulation of high permeability zones in fractured rock to hydraulic connection data a simulated annealing algorithm generates three dimensional 3 d realizations conditioned to borehole data inferred hydraulic connections between packer isolated borehole intervals and an indicator fracture zone or background k bedrock variogram model of spatial variability we apply the method to data from the u s geological survey mirror lake site in new hampshire where connected high permeability fracture zones exert a strong control on fluid flow at the hundred meter scale single well hydraulic packer tests indicate where permeable fracture zones intersect boreholes and multiple well pumping tests indicate the degree of hydraulic connection between boreholes borehole intervals connected by a fracture zone exhibit similar hydraulic responses whereas intervals not connected by a fracture zone exhibit different responses our approach yields valuable insights into the 3 d geometry of fracture zones at mirror lake statistical analysis of the realizations yields maps of the probabilities of intersecting specific fracture zones with additional wells inverse flow modeling based on the assumption of equivalent porous media is used to estimate hydraulic conductivity and specific storage and to identify those fracture zone geometries that are consistent with hydraulic test data

estimation of flow properties using surface deformation and head data a trajectory based approach 1 a trajectory based algorithm provides an efficient and robust means to infer flow properties from surface deformation and head data the algorithm is based upon the concept of an arrival time of a drawdown front which is defined as the time corresponding to the maximum slope of the drawdown curve the technique involves three steps the inference of head changes as a function of position and time the use of the estimated head changes to define arrival times and the inversion of the arrival times for flow properties trajectories computed from the output of a numerical simulator are used to relate the drawdown arrival times to flow properties the inversion algorithm is iterative requiring one reservoir simulation for each iteration the method is applied to data from a set of 14 tiltmeters located at the raymond quarry field site in california using the technique i am able to image a high conductivity channel which extends to the south of the pumping well the presence of this permeable pathway is supported by an analysis of earlier cross well transient pressure test data

characterizing subsurface hydraulic heterogeneity of alluvial fan using riverstage fluctuations strategic environmental research and development program serdp er 1365 environmental security and technology certification program estcp er201212 nsf ear from the united state 1014594 jilin university from department of education china global expert award through tianjin normal university from the thousand talents plan of tianjin city from china taiwan typhoon and flood research institute national applied research laboratories natural science foundation of china 51409029

a field assessment of high resolution aquifer characterization based on hydraulic travel time and hydraulic attenuation tomography 1 in this study the potential of an inversion approach based on hydraulic travel time and hydraulic attenuation tomography was assessed both hydraulic travel time and hydraulic attenuation tomography are based on the transformation of the transient groundwater flow equation into the eikonal equation using an asymptotic approach the eikonal equation allows the calculation of pressure propagation and attenuation along trajectories which is computationally efficient the attenuation and travel time based inversion approaches are naturally complementary hydraulic travel times are determined by the hydraulic diffusivity a combination of hydraulic conductivity and specific storage whereas the attenuation is determined solely by specific storage the potential of our hydraulic tomographical approach was investigated at a well characterized sand and gravel aquifer located in the leine river valley near gottingen germany the database for the hydraulic inversion consists of 392 cross well slug interference tests performed between five wells in which the positions of the sources injection ports and the receivers observation ports isolated with double packer systems were varied between tests the results have shown that the combination of hydraulic travel time and hydraulic attenuation tomography allows the reconstruction of the diffusivity and storage distribution in two and three dimensions with a resolution and accuracy superior to that possible with type curve analysis

an analysis of earth tide induced groundwater flow in eastern botswana abstract earth tide induced groundwater level fluctuations with a maximum amplitude of 12 cm have been observed in a fractured shale aquifer in eastern botswana comparison of the oscillations with the tidal variations in the gravity field of the earth revealed a remarkable phase advance of the groundwater tides relative to the earth tides the phase shift ranges from 28 1 h for the semi diurnal frequency group to about 47 4 h for the diurnal group of the tidal spectrum a theoretical model is presented that attributes the marked amplitude to a high compressibility of the aquifer and explains the positive phase shift through a periodic groundwater flow between the shale basin and the surrounding aquifers the horizontal hydraulic gradient causing this groundwater movement is assumed to be induced by the tidal strain differentiation between the compressible shale and the more rigid arenitic and dolomitic adjoining rocks the magnitude of the generated groundwater flow is of the order of 14 m 3 h 1 at the outer fringe of the area involved the tidal dilatation in the centre of the shale basin is about 30 times the theoretical value for homogeneous conditions

general solution for tidal behavior in confined and semiconfined aquifers considering skin and wellbore storage effects tidal analysis provides a cost effective way of estimating aquifer properties tidal response models that link aquifer properties with tidal signal characteristics such as phase and amplitude hav

characterization of aquifer heterogeneity using transient hydraulic tomography 1 hydraulic tomography is a cost effective technique for characterizing the heterogeneity of hydraulic parameters in the subsurface during hydraulic tomography surveys a large number of hydraulic heads i e aquifer responses are collected from a series of pumping or injection tests in an aquifer these responses are then used to interpret the spatial distribution of hydraulic parameters of the aquifer using inverse modeling in this study we developed an efficient sequential successive linear estimator ssle for interpreting data from transient hydraulic tomography to estimate three dimensional hydraulic conductivity and specific storage fields of aquifers we first explored this estimator for transient hydraulic tomography in a hypothetical one dimensional aquifer results show that during a pumping test transient heads are highly correlated with specific storage at early time but with hydraulic conductivity at late time therefore reliable estimates of both hydraulic conductivity and specific storage must exploit the head data at both early and late times our study also shows that the transient heads are highly correlated over time implying only infrequent head measurements are needed during the estimation applying this sampling strategy to a well posed problem we show that our ssle can produce accurate estimates of both hydraulic conductivity and specific storage fields the benefit of hydraulic tomography for ill posed problems is then demonstrated finally to affirm the robustness of our ssle approach we apply the ssle approach to a hypothetical three dimensional heterogeneous aquifer

stochastic simulations of steady state unsaturated flow in a three layer heterogeneous dual continuum model of fractured rock abstract unsaturated flow through fractured rocks is a concern in the siting and performance of waste disposal facilities such as the proposed geological repository at yucca mountain nevada we simulated a small two dimensional cross section of welded volcanic tuff representative of yucca mountain stratigraphy using spatially correlated randomly heterogeneous fracture permeability fields and homogeneous matrix permeability continua representing various degrees of welding ten realizations each of fracture permeability fields for four different variances 2 0 5 1 0 1 5 and 2 0 were generated by the direct fourier transform method robin m j l gutjahr a l sudicky e a wilson j l 1993 cross correlated random field generation with the direct fourier transform method water resour res 29 7 2385 2398 independently for the welded tiva canyon tuff tcw the non welded paintbrush tuff ptn and the welded topopah spring tuff tsw the latter being the proposed primary repository horizon numerical simulations were run for steady state flow at three different uniform water flux boundary conditions boundary conditions along the sides were impermeable and the base was open to gas and liquid flow numerical simulations were performed using the dual continuum two phase flow simulator metra which represents matrix and fractures as dual overlapping continua where liquid flux between continua can be restricted by a uniform factor fracture matrix interaction was modeled as being less restricted in the ptn as compared to the tcw tsw heterogeneous fracture permeability fields generated strong preferential flow in the tcw tsw fracture continuum and significant preferential flow in the uniformly permeable ptn matrix continuum flow focusing led to a local increase in saturation which in turn increased relative permeability to water along the preferential pathways causing water to flow faster the development of the preferential pathways reduced the wetted surface area for fracture matrix interaction leaving a large volume of the rock isolated from the preferential flow pathways statistical analysis of water flux values in the three units showed that the magnitude of the ensemble variance indicating preferential flow pathways increased with both the variance of fracture permeability and the water flux boundary condition reaching a plateau in the tcw tsw fracture continuum units after flowing approximately 10 correlation scales of the vertical fracture permeability ensemble covariance of water flux normal to the layering revealed long range correlations in all units which is longer than the correlation length of the fracture permeability fields this suggests that the water flux boundary condition influences preferential flow in unsaturated dual continua media these results suggest that careful analysis of information on fracture permeability variability obtained from pneumatic and hydraulic tests is an important component in understanding deep percolation processes

a salt tracer test monitored with surface ert to detect preferential flow and transport paths in fractured karstified limestones in hard rock aquifers fractured zones constitute adequate drinking water exploitation areas but also potential contamination paths one critical issue in hydrogeological research is to identify characterize and monitor such fractured zones at a representative scale a tracer test monitored with surface electrical resistivity tomography ert could help by delineating such preferential flow paths and estimating dynamic properties of the aquifer however multiple challenges exist including the lower resolution of surface ert compared with crosshole ert the finite time that is needed to complete an entire data acquisition and the strong dilution effects we conducted a natural gradient salt tracer test in fractured limestones to account for the high transport velocity we injected the salt tracer continuously for four hours at a depth of 18 m we monitored its propagation with two parallel ert profiles perpendicular to the groundwater flow direction concerning the data acquisition we always focused

predictive modelling of hydraulic head responses to dipole flow experiments in a fractured karstified limestone aquifer insights from a comparison of five modelling approaches to real field experiments summary five modelling approaches were tested against a well studied limestone aquifer constituting the hydrogeological experimental site hes of poitiers france the modelling exercise consisted of predicting the drawdown responses of a series of observation wells for two dipole pumping injection flow experiments involving two distinct well pairs at the hes the differences between model predictions appear to be mainly related to the hydraulic datasets used for model parameterisation and to a much lesser extent to the conceptual modelling approach equivalent porous medium vs discrete fracture networks the model dimensionality two dimensional vs three dimensional and or the parameterisation approach forward vs inverse despite the abundance and diversity of calibration parameterisation data all of the models failed to predict the drawdowns with a reasonable degree of accuracy only the order of magnitude of the drawdowns was correctly predicted by three of the five models whereas all models failed to predict the drawdown behaviour at both intermediate and late times the primary source of error is attributed to a lack of information in the single well pumping test data which did not capture the multi permeability structure of the aquifer as revealed a posteriori by the responses to dipole flow experiments this highlights the need to develop novel or improved approaches to characterise the hydraulic properties of limestone aquifers

numerical evaluation of volumetric weighted mean transmissivity estimates in laterally heterogeneous aquifers summary most previous investigations to evaluate the effective or average transmissivity in heterogeneous environments have used calculations based on areas to weight the effects of each heterogeneity analysis of spatial volumetric variations within the cone of depression expressed at the potentiometric surface offers a more general solution to evaluate the meaning of transmissivity t and storativity s values derived from aquifer tests in these environments the cooper jr h h jacob c e 1946 a generalized graphical method for evaluating formation constants and summarizing well field history eos trans agu 27 4 526 534 method is used to demonstrate that t variations reflected in slope changes in plots of the pumping well drawdown data correspond to changes in the volumetric weighted mean transmissivity vwmt over time lognormal distributions of transmissivity are represented by block heterogeneities within two simulated aquifers for both spatially random and spatially correlated data sets by analyzing the volumetric evolution of the cone of depression observed in the potentiometric surface the nature of t averaging within the cone of depression as a function of time is illustrated volumetric analysis shows that the average aquifer t varies with time as the cone of depression progressively envelops different heterogeneities the initial trend is controlled primarily by the heterogeneities directly surrounding the pumping center if steady shape conditions are not achieved late time vwmt values do not approach an asymptotic limit

estimating transmissivity from single well pumping tests in heterogeneous aquifers although aquifers are naturally heterogeneous the interpretation of pumping tests is commonly performed under the assumption of aquifer homogeneity this yields interpreted hydraulic parameters averaged over a domain of uncertain extent which disguises their relation to the underlying heterogeneity in this study we numerically investigate the sensitivity of the transient drawdown at the pumping well to nonuniform distributions of transmissivity in confined aquifers frechet kernels and their time derivative are used to estimate two spatially averaged transmissivities denoted the equivalent and interpreted transmissivity teq and tin respectively for the case of single well pumping tests interrelating teq and tin is achieved by modeling tin in terms of a distance dependent radially heterogeneous field in weakly heterogeneous aquifers teq approximates tpw the local transmissivity at the pumped well with increasing degree of heterogeneity teq deviates from tpw as pumping propagates tin starts at tpw approaching the spatial geometric mean of transmissivity during late pumping times limits of the proposed spatial weighting functions are investigated by treating the interpreted storativity sest as an indicator for flow connectivity it is shown numerically that the spatial weights for teq and tin agree well to the underlying heterogeneity if sest 1 finally implications for applying the concepts of teq and tin to heterogeneous domains and for real world applications are discussed it is found that time dependent spatial averages of tin agree well with estimates of the interpreted transmissivity from the continuous derivation method

transient pumping well flow in weakly heterogeneous formations 1 the solution of pumping well flow serves for identifying aquifer s properties most results available in the literature assume homogeneous aquifers or at most stratified structures this study investigates the unsteady well flow in heterogeneous aquifers by modeling the hydraulic conductivity as a three dimensional stationary random function of axisymmetric anisotropy and gaussian correlations the main result of the investigation is the mean drawdown in a transient flow toward a fully penetrating well pumping at a constant rate the solution is obtained in terms of one quadrature over time and is easily calculated closed form approximations of the mean head are developed for moderate and large times the mean drawdowns derived in the study generalize the theis and copper and jacob distributions for aquifers of constant transmissivity it is shown that the transmissivity which is identified by using the cooper and jacob asymptotic is precisely the effective conductivity for uniform horizontal flow khefu this is compared with the finding that the equivalent conductivity for the steady state flow approaches khefu with distance from the well indelman et al 1996

on phase shifts in periodic well fluctuations summary for the case of a well completely penetrating a confined aquifer of infinite extent an analysis is made of the flow processes in the well aquifer system due to periodic pressure variations like earth tides and barometric tides it is shown that the earth tides lead to well fluctuations with a negative phase difference phase lag while the barometric tides cause well fluctuations with a positive phase difference phase advance in both cases the amplitudes and phases of the well fluctuations depend on frequency and are therefore different for the individual components of the tidal spectra these frequency characteristics need to be studied more carefully than is the case now a schematic model of a device is described that could not only be used for this purpose but also for the determination of the specific storage ss and the conductivity k the method would be closely related to the well known slug or bail tests

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

a temporal sampling strategy for hydraulic tomography analysis 1 this paper investigates optimal sampling times of drawdowns for the analysis of hydraulic tomography ht survey the investigation was carried out by analyzing the spatial and temporal evolution of cross correlations between the head responses at an observation well and transmissivity t and storage coefficient s properties during a pumping test in homogeneous and heterogeneous aquifers the analysis shows that the cross correlation between the head and s values is limited to the region between the observation and the pumping well in the aquifers it reaches the highest value near the early time tm and decays to zero afterwards the time tm is approximately equal to the time t0 at which the extrapolated drawdown from the first straight line portion of an observed drawdown log time plot becomes zero at early times the high cross correlation between the head and t is confined to the region between the observation and the pumping well this region then evolves into two humps one on each side of the circular region encompassing the observation well and the pumping well the size of the two humps expands and their values reach the maximum as flow reach steady state as a consequence we hypothesize that pairs of head data at t0 and those at either the steady state or a late time during an ht survey could yield the best estimates of the heterogeneous t and s fields results from numerical experiments have verified this hypothesis and demonstrated that this sampling strategy is generally applicable even when the boundary condition is unknown we therefore recommend in principle that 1 carrying out pumping tests of ht surveys for sufficiently long period of time such that drawdown reaches the entire area of interest and 2 using a constant head or zero drawdown for all boundaries during the inverse modeling analysis

on the importance of geological data for three dimensional steady state hydraulic tomography analysis at a highly heterogeneous aquifer aquitard system abstract hydraulic tomography ht has been shown to map subsurface heterogeneity accurately through the joint interpretation of multiple pumping tests previous research has shown that smooth hydraulic conductivity k estimates are obtained beyond where pumping observation data are available using the geostatistical inversion approach when the inversion begins with a homogeneous k and when data densities are not high however geological data are typically available through outcrops and borehole logs to provide geological variability therefore we investigate the usefulness of geological data for ht analysis at a highly heterogeneous field site by 1 comparing calibrated geological models of two different resolutions to two homogeneous and four highly parameterized geostatistical inverse models in terms of both model calibration and validation performances as well as correspondence of estimated k values with permeameter estimated k profiles along boreholes and 2 using geological models as prior information for the geostatistical inversion approach results reveal that the simultaneous calibration of geological models to seven pumping test data yields k values that correctly reflect the general patterns of vertical distributions of permeameter estimated k we also find that the geostatistical inversion approach using a geological model as prior information performs better for both model calibration and validation than using a homogenous k as a prior and more importantly improves the correspondence of k estimates to permeameter test results along wells as well as in preserving geological features where drawdown measurements are lacking overall our results suggest the joint use of both geological and pumping test data for ht analysis when accurate geological data are available

local surface mass balance reconstruction from a tephra layer a case study on the northern slope of mýrdalsjokull iceland most icelandic glaciers show high accumulation rates during winter and strong surface melting during summer although it is difficult to establish and maintain mass balance programs on these glaciers mass balance series do exist for several of the ice caps bjornsson and others 2013 we make use of the frequent volcanic eruptions in iceland which cause widespread internal tephra layers in the ice caps to reconstruct the surface mass balance smb in the ablation zone this method requires information about surface geometry and ice velocity derived from remote sensing information in addition the emergence angle of the tephra layer needs to be known as a proof of concept we utilize a prominent tephra layer of the m rdalsjokull ice cap to infer local smb estimates in the ablation area back to 1988 using tephra layer outcrop locations across the glacier at different points in time it is possible to determine local mass changes loss and redistribution for a large part of the ablation zone without the use of historic elevation models which often are not available

the use of remote sensing data for mass balance studies at mýrdalsjokull ice cap iceland a series of satellite images of myrdalsjokull iceland was analyzed in view of their value for mass balance investigations a combination of optical satellite images from the aster sensor and synthetic aperture radar data from ers 2 and envisat asar proved very useful the glacier margin of myrdalsjokull was delineated on aster images from summer and winter 2004 with a time series of summer asar images it was possible to monitor the temporal and spatial development of the transient snowline tsl throughout the year 2004 as well as the firn line fl at the end of the balance year an inverse function was applied to visually enhance detail in the radar imagery winter radar images were not useful for mass balance observations because of frequent surface melting which prevented the transparency of the snow cover for c band microwaves interannual mass balance fluctuations were observed by comparing three radar images acquired in late summer 1998 1999 and 2004 respectively these fluctuations follow the same trend as the annual mean air temperature which shows a strong increasing trend between 1999 and 2004 an accumulation area ratio of 0 43 was determined for 2004 indicating clear negative mass balance conditions monitoring the tsl fl with radar summer images for mass balance studies rather than the equilibrium line el is suggested for large ice caps in maritime climates

an application of hydraulic tomography to a deep coal mine combining traditional pumping tests with water inrush incidents abstract water inrush incidents threaten the safety of coal mining understanding of hydrogeologic parameter distributions is critical for preventing water related hazards in coal mines during the deep mining 1000 m under the north china plain water from water bearing strata discharges into coal seams through geologic conduits i e water inrush due to the fractured zone under the floor of working faces in this study a water inrush incident was exploited as an active stimulus a 3d groundwater flow model was built for the eighth member of the middle ordovician system in xingdong coal mine using this model and an inverse approach we first checked if the data from the incident and an independent pumping test carry non redundant information about the heterogeneity of the mine afterward we combined these datasets to conduct a large scale approximately 10 km hydraulic tomography ht analysis the estimated hydraulic conductivity distribution from the ht analysis is found consistent with the distribution of known geologic faults that is a cluster of faults is characterized as a high conductivity zone a high conductivity zone is identified at locations close to the water inrush location which is the high cement consumption zone during the grouting project finally results of this study promote exploiting the water inrush events as a ht survey for mapping geologic structures over a large area

a view toward the future of subsurface characterization cat scanning groundwater basins 1 in this opinion paper we contend that high resolution characterization monitoring and prediction are the key elements to advancing and reducing uncertainty in our understanding and prediction of subsurface processes at basin scales first we advocate that recently developed tomographic surveying is an effective and high resolution approach for characterizing the field scale subsurface fusion of different types of tomographic surveys further enhances the characterization a basin is an appropriate scale for many water resources management purposes we thereby propose the expansion of the tomographic surveying and data fusion concept to basin scale characterization in order to facilitate basin scale tomographic surveys different types of passive basin scale cat scan technologies are suggested that exploit recurrent natural stimuli e g lightning earthquakes storm events barometric variations river stage variations etc as sources of excitations along with implementation of sensor networks that provide long term and spatially distributed monitoring of excitation as well as response signals on the land surface and in the subsurface this vision for basin scale subsurface characterization faces many significant technological challenges and requires interdisciplinary collaborations e g surface and subsurface hydrology geophysics geology geochemistry information and sensor technology applied mathematics atmospheric science etc we nevertheless contend that this should be a future direction for subsurface science research

three dimensional imaging of aquifer and aquitard heterogeneity via transient hydraulic tomography at a highly heterogeneous field site abstract previous studies have shown that geostatistics based transient hydraulic tomography tht is robust for subsurface heterogeneity characterization through the joint inverse modeling of multiple pumping tests however the hydraulic conductivity k and specific storage ss estimates can be smooth or even erroneous for areas where pumping observation densities are low this renders the imaging of interlayer and intralayer heterogeneity of highly contrasting materials including their unit boundaries difficult in this study we further test the performance of tht by utilizing existing and newly collected pumping test data of longer durations that showed drawdown responses in both aquifer and aquitard units at a field site underlain by a highly heterogeneous glaciofluvial deposit the robust performance of the tht is highlighted through the comparison of different degrees of model parameterization including 1 the effective parameter approach 2 the geological zonation approach relying on borehole logs and 3 the geostatistical inversion approach considering different prior information with without geological data results reveal that the simultaneous analysis of eight pumping tests with the geostatistical inverse model yields the best results in terms of model calibration and validation we also find that the joint interpretation of long term drawdown data from aquifer and aquitard units is necessary in mapping their full heterogeneous patterns including intralayer variabilities moreover as geological data are included as prior information in the geostatistics based tht analysis the estimated k values increasingly reflect the vertical distribution patterns of permeameter estimated k in both aquifer and aquitard units finally the comparison of various tht approaches reveals that differences in the estimated k and ss tomograms result in significantly different transient drawdown predictions at observation ports

aquifer parameter estimation using an incremental area method theoretical well functions have been derived over the years to predict ground water level behaviour in aquifer systems under stress owing to groundwater extraction the drawdown data collected during pump tests are typically analysed using graphical curve matching procedures to estimate aquifer parameters based on these well functions difficulty in aquifer characteristic identification and parameter estimation may arise when the field data do not perfectly match the drawdown curves obtained from the well functions the present study provides a new method for the interpretation of aquifer pump tests which supplements the existing curve matching procedures in case ideal conditions do not exist the proposed method provides a greater degree of flexibility in the data analysis for diagnostic tool purposes the method referred to as the incremental area method iam is based on integrating the logarithmic based drawdown curves within a discrete time and matching the results with a corresponding time integral of the theis 1935 well function which governs ideal confined aquifers the application of the proposed method to synthetically generated data and field data showed that iam represents a viable method which yields information on potential non idealness of the aquifer and provides aquifer parameter estimates thus potentially overcoming drawdown data curve matching difficulties copyright 2011 john wiley sons ltd

inferring spatial distribution of the radially integrated transmissivity from pumping tests in heterogeneous confined aquifers 1 hydrologists routinely analyze pumping test data using conventional interpretation methods that are based on the assumption of homogeneity and that consequently yield single estimates of representative flow parameters however natural subsurface formations are intrinsically heterogeneous and hence the flow parameters influencing the drawdown vary as the cone of depression expands in time in this paper a novel procedure for the analysis of pumping tests in heterogeneous confined aquifers is developed we assume that a given heterogeneous aquifer can be represented by a homogeneous system whose flow parameters evolve in time as the pumping test progresses at any point in time the interpreted flow parameters are estimated using the ratio of the drawdown and its derivative observed at that particular time the procedure is repeated for all times yielding time dependent estimates of transmissivity ti t and storativity si t based on the analysis of the sensitivity of drawdown to inhomogeneities in the t field the time dependent interpreted transmissivity values are found to be a good estimate of tg r the geometric mean of the transmissivity values encompassed within a progressively increasing radius r from the well the procedure is illustrated for gaussian heterogeneous fields with ln t variances up to a value of 2 the impact of the separation distance between the pumping well and observation point on data interpretation is discussed the results show that information about the spatial variability of the transmissivity field can be inferred from time drawdown data collected at a single observation point

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

investigations of water inrushes from aquifers under coal seams in many coal mines limestone confined aquifers underlie coal seams during coal extraction from these mines water inrushes occur frequently with disastrous consequences this paper introduces the hydrogeological conditions of the coal mines and the potential water inrush disasters from aquifers under coal seams it then presents the water inrush mechanism the main factors which control water inrushes include strata pressure mining size geologic structures and the water pressure in the underlying aquifer analysis shows that reduction of confinement due to mining is the major cause of the water conducting failure in the floor strata the depth of the failure zone is strongly dependent on the mining width this paper also presents field observation results of the water conducting failure in the floor strata and applies the finite element method coupled with stress dependent permeability to analyze hydraulic conductivity enhancement due to coal extraction finally theoretical and empirical methods to predict water inrushes are given and technical measures for improving mine design and safety for coal extraction over aquifers are presented these measures include fault and fracture grouting and mining method modification such as changing long wall to short wall mining

hydrogeological analysis and salvage of a deep coalmine after a groundwater inrush this paper presents a case history of the permanent salvage of the sanhejian coalmine in china after a sudden groundwater inrush which includes emergency responses hydrogeological analyses and design and performance of bulkheads the inrush accident occurred in october 2002 in the mined out area with a high water pressure of 7 6 mpa and a high water temperature of 51 c the emergency response quickly followed up to provide the time required to perform a detailed hydrogeological analysis to identify the source and pathway of groundwater the sanhejian coalmine is geologically located in the tengxian anticline hydrogeological setting the sunshidian fault the northern boundary of the mine was assumed impermeable in the original hydrogeological report after the accident and hydrogeological analysis this assessment was revised and the fault was considered to be permeable the sunshidian fault connects the strata in the mine and the excellent water productive middle ordovician majiagou formation in the core of the tengxian anticline it was concluded that the water inrush was from the underlying ordovician karst aquifer and the pathway was a hidden tectonic structure in the strata overlying the aquifer this assessment served as the guideline for salvaging the mine in this project after a detailed technical and economic analysis a concrete bulkhead design was selected from several alternatives including dewatering and surface grouting the performance of the bulkheads has been sufficient for the last 6 years since their construction this case history shows that the hydrogeological analysis plays an essential role in successfully salvaging the coalmine from the water inrush by identifying the source and pathway of groundwater

impact of karst water on coal mining in north china coalfields in north china encompass more than ten provinces they contain six to seven coal seams in the permo carboniferous strata the lower three seams account for 37 of the total reserves and are threatened with intrusion of karst water from the underlying ordovician limestone hundreds of water inrush incidences have occurred in which a large amount of water suddenly flows into tunnels or working faces under high potentiometric pressure over 50 mines have been flooded over the last 30 years large scale dewatering or depressurizing of the karst aquifer was considered essential to avoid water inrushes and keep the mines safely operational this practice however has caused sinkholes dry springs water supply shortage and groundwater contamination in the surrounding areas one alternative water control measure is to make full use of the rock layer between the coal seam and the karst aquifer as a protective barrier to prevent or constrain water flow from the underlying aquifer into the mines grouting is effective when the hydrogeological conditions are favorable to this technique proper design of the grouting program and experience of the contractor are also important for a successful application

the identification of fault zones in deep karst aquifer of north china coal mine using parallel directional well logs water inrush from ordovician karst aquifer in north china coal mine has become a key issue on underground coal mining to address this problem it is necessary to identify fault zones because fault zones might connect limestone aquifers and coal seams enabling ordovician karst water to enter the mine in the study area a series of parallel directional holes were drilled along ordovician limestone at depths between 70 and 90 m under ordovician limestone boundary to conveniently detect fault zones and govern mine water disasters a series of natural gamma ray logging while drilling grlwd were undertaken the entire detecting region can be comprehensively covered by several directional borehole groups then fast fourier transform and short time fourier transform approaches were employed on the basis of grlwd data and geological data to extract faults information a segmented identification method for deep fault zones was established in this study this method can be used to markedly improve the identification of fault zones within ordovician limestone or the unitary lithology formation and provide crucial information relevant for deep coal mining safety

an accumulation map for the greenland dry snow facies derived from spaceborne radar 1 an important component of ice sheet mass balance calculations is the snow accumulation rate traditionally determined across the ice sheet from interpolated ice core data we derive an accumulation rate map within the greenland dry snow facies using c band radar backscatter and the mean annual temperature values for the backscatter were obtained from the ers 1 synthetic aperture radar mosaic acquired during september november 1992 an empirical equation based on elevation and latitude is used to determine the mean annual temperature we examine the influence of accumulation rate and mean annual temperature on c band 5 3 ghz radar backscatter using a forward model which incorporates snow metamorphosis and radar backscatter components our model is run over a range of accumulation and temperature conditions consistent with the greenland dry snow facies on the basis of our modeled results a look up table is generated which uniquely maps the measured radar backscatter and mean annual temperature to accumulation rate our results compare favorably 15 4 average difference with 124 in situ accumulation rate measurements falling within our study area we attribute some of the differences to 1 unreliable in situ data points which were based on a single year s accumulation and 2 a systematic underestimate of accumulation rate by our forward model in the low accumulation regions associated with the northern portion of our map with questionable data points and those above 77 n removed the average differences were less than 10 3 as determined from 73 ice cores

cross correlation analysis and information content of observed heads during pumping in unconfined aquifers 1 using a first order cross correlation analysis this paper investigates the relationship between observed heads and hydraulic properties in the saturated and vadose zones at different times and locations of three dimensional unconfined aquifers during pumping tests cross correlation analysis is a weighted sensitivity analysis casted into a stochastic framework it determines the relative impact of each parameter with respect to others in time and space on the observed heads according to uncertainty or spatial variability of each parameter it reveals the information content in measured drawdowns about heterogeneity during a pumping test in an unconfined aquifer which is critical for aquifer parameter estimation based on a synthetic numerical example our cross correlation analysis reveals that heads in the saturated zone at late times carry the greatest nonsymmetrically weighted information content about the hydraulic conductivity ks distribution within the cone of depression on the other hand heads in the saturated zone at early times contain the most information about the specific storage ss heterogeneity in a narrow region between the observation and pumping locations during intermediate and late times heads in the saturated zone largely reflect the effects of saturated water content s and pore size parameter in the thin unsaturated region near the water table above the pumping and observation locations at last heads in the vadose zone at late times carry the greatest information about s and around the observation point

permeability tensor for discontinuous rock masses rock masses which commonly contain a large number of discontinuities are treated as homogeneous anisotropic porous media to formulate the corresponding permeability tensor this has been successfully achieved by introducing a symmetric tensor crack tensor which depends only on the geometry of the related cracks aperture size and orientation the principal directions associated with the symmetric crack tensor are coaxial with those of the permeability tensor the first invariant of the crack tensor is proportional to the mean permeability while the deviatoric part is related to the anisotropic permeability these results are well supported by numerical experiments on the permeability of cracked media by long remer wilson and witherspoon an actual rock mass moderately jointed granite was studied to see whether the crack tensor can be determined in situ stereology based on geometrical statistics provides a sound basis for determining the crack tensor in situ the crack tensor is obtained by

current plate movements across the mid atlantic ridge determined from 5 years of continuous gps measurements in iceland 1 we analyze data spanning up to 5 years from 18 continuous gps stations in iceland computing daily positions of the stations with three different high level geodetic processing software packages we observe large scale crustal deformation due to plate spreading across iceland the observed plate divergence between the north american and the eurasian plates is in general agreement with existing models of plate motion spreading is taken up within a 100 150 km wide plate boundary zone that runs through the island of the two parallel branches of the plate boundary in south iceland the eastern volcanic zone is currently taking up the majority of the spreading and little is left for the western volcanic zone the plate boundary deformation field has been locally and temporarily affected in south iceland by two mw 6 5 earthquakes in june 2000 inflation at katla volcano during 2000 to 2004 and an eruption of hekla volcano in february 2000 all stations with significant vertical velocities are moving up relative to the reference station reyk with the highest velocity exceeding 20 mm yr in the center of the island

a continuum representation of fracture networks part ii application to the aspo hard rock laboratory abstract a method to represent fracture networks in a continuum model is evaluated by an application to the aspo hard rock laboratory hrl the basic approach of the method is to first generate a fracture network based on data from field measurements and then represent the network as grid cell conductivities using a staggered grid arrangement it is argued that the resulting conductivity fields capture the correlation and anisotropy structures as well as the mean conductivity of the rock in a realistic way the main objective is to evaluate if the suggested method can be used in an application to a real site the objective is formulated in three questions can the method utilize available field data can the generated fields be calibrated and conditioned and are realistic distributions of pressure flow and density obtained from the application to the aspo hrl it is concluded that the hydraulic conductivity fields generated by the suggested method can utilize field data and be calibrated it is also demonstrated that realistic distributions of pressure flow and density can be simulated

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

evidence of inception horizons in karst conduit networks this paper outlines the conclusion from an analysis of 18 large cave systems around the world comprising more than 1500 km of conduits the 3d geometry of complex cave systems have been analysed in relation to their geological context as well as their hydrogeological boundary conditions the methodology allowed for the first time statistical evidence of the inception horizon concept thereby it confirms that the development of karst conduits under phreatic conditions is strongly related to a restricted number of so called inception horizons an inception horizon is a part of a rock succession that is particularly susceptible to the development of karst conduits because of physical lithological or chemical deviation from the predominant carbonate facies within the limestone sequence it passively or actively favours the localisation of dissolutional voids

the influence of nonuniform transmissivity and storativity on drawdown although the existence of spatial variability in hydrogeological parameters is widely recognized most analyses of pumping test data are performed under the assumption that the aquifer is adequately characterized by a few parameters for example constant transmissivity constant storativity distance to a barrier and well skin even if the possibility of variability is recognized pumping tests are often thought to investigate the region between a pumping well and an observation well recently however investigations of the sensitivity of pumping test data to radially symmetric nonuniform flow properties have shown that the drawdown at an observation well is insensitive to transmissivity and storativity of the region between the pumping well and the observation well in this paper i use a perturbation approach to derive the frechet derivatives and kernels for the effect of two dimensional areal variations in transmissivity and storativity on drawdown at an observation well frechet derivatives and kernels are related to sensitivity coefficients but their definition is independent of zonation examination of the frechet kernels at large distances from the pumping and observation wells shows that the area of investigation of a pumping test is bounded by an ellipse that encloses both wells this study also shows that observation well drawdown is relatively sensitive to near well transmissivity variation especially if the nonuniformity is not radially symmetric about the well

mass changes of outlet glaciers along the nordensjkold coast northern antarctic peninsula based on tandem x satellite measurements we analyzed volume change and mass balance of outlet glaciers of the northern antarctic peninsula over the period 2011 to 2013 using topographic data of high vertical accuracy and great spatial detail acquired by bistatic radar interferometry of the tandem x terrasar x satellite formation the study area includes glaciers draining into the larsen a larsen inlet and prince gustav channel embayments after collapse of buttressing ice shelves in 1995 the glaciers became tidewater calving glaciers and accelerated resulting in increased ice export downwasting of most glaciers is going on but at reduced rates compared to previous years in accordance with deceleration of ice flow the rate of mass depletion is 4 2 0 4 gt a 1 with the largest contribution by drygalski glacier amounting to 2 2 0 2 gt a 1 on the technological side the investigations demonstrate the capability of satellite borne single pass radar interferometry as a new tool for accurate and detailed monitoring of glacier volume change

time series analyses for karst river interactions assessment case of the coulazou river southern france summary in many karst systems throughout the world numerous karst features facilitate the exchange of water between the surface the vadose zone and the saturated zone of the aquifer these interactions play actually a prominent role in the ground and surface waters circulation this study aims at assessing karst river interactions by the way of flood hydrograph analysis and new tools for time series analysis in this field of research as in many others binary karst system the captured waters of the coulazou river travel through conduits and preferential flow paths in the vadose zone and join the saturated zone of the aquifer this river is an ephemeral river in a mediterranean context where rapid and intense floods occur each year this hydrologic behaviour is appropriate to study the transfer of a flood through a karst area the water level in caves the rainfall all over the karst aquifer catchment area the piezometric level within the karst aquifer and the discharge in the river upstream and downstream of the karst aquifer are measured in order to understand the karst river exchanges during a flood the modification of the surface flows in the river is treated as a linear time invariant system lti system correlation and spectral analyses are used to understand how the lti system dissipates or enhances the flood wave energy for several floods the frequency response function estimations are interpreted in term of flood wave modification through the karst area in this way according to the initial state of the karst river system the autogenic and or allogenic recharge of the aquifer may induce surge flows and a significant karst contribution to surface flows

the effect of inflation on the morphology derived rheological parameters of lava flows and its implications for interpreting remote sensing data a case study on the 2014 2015 eruption at holuhraun iceland abstract morphology derived lava flow rheology is a frequently used tool in volcanology and planetary science to determine rheological parameters and deduce the composition of lavas on terrestrial planets and their moons these calculations are usually based on physical equations incorporating 1 lava flow driving forces gravity slope and flow rate and 2 morphological data such as lava flow geometry flow width height or shape of the flow outline all available methods assume that no geometrical changes occur after emplacement and that the measured flow geometry reflects the lava s apparent viscosity and or yield strength during emplacement it is however well established from terrestrial examples that lava flows may inflate significantly after the cessation of flow advance this inflation affects in turn the width to height ratio upon which the rheological estimates are based and thus must result in uncertainties in the determination of flow rheology as the flow height is one of the key parameters in the morphology based deduction of flow properties previous studies have recognized this issue but to date no assessment of the magnitude of this error has been presented this is likely due to a lack of digital elevation models dems at sufficiently high spatial and temporal resolution the 2014 15 holuhraun eruption in central iceland represents one of the best monitored large volume 1 5 km3 lava flow fields 85 km2 to date an abundance of scientific field and remote sensing data were collected during its emplacement moreover inflation plays a key role in the emplacement dynamics of the late stage of the lava field here we use a time series of high resolution dems acquired by the tandem x satellite mission prior during and after the eruption to evaluate the error associated with the most common methods of deriving lava flow rheology from morphological parameters used in planetary science we can distinguish two dominant processes as sources of error in the determination of lava flow rheology from morphology 1 wholesale inflation of lava channels and 2 post halting inflation of individual lava toes these result in a 2 4 to 17 fold overestimation of apparent viscosity and a 0 7 to 2 4 fold overestimation of yield strength when applied in planetary sciences this overestimation in rheological parameters translates directly to an overestimation of the respective lavas silica content we conclude that although qualitatively informative morphological analysis is insufficient to discern lava rheology and composition instead in situ analysis together with high resolution remote sensing data is needed to properly constrain the compositions involved in planetary volcanism

effects of turbulence on hydraulic heads and parameter sensitivities in preferential groundwater flow layers 1 a conduit flow process cfp for the modular finite difference ground water flow model modflow 2005 has been created by the u s geological survey an application of the cfp on a carbonate aquifer in southern florida is described this application examines 1 the potential for turbulent groundwater flow and 2 the effects of turbulent flow on hydraulic heads and parameter sensitivities turbulent flow components were spatially extensive in preferential groundwater flow layers with horizontal hydraulic conductivities of about 5 000 000 m d 1 mean void diameters equal to about 3 5 cm groundwater temperature equal to about 25 c and critical reynolds numbers less than or equal to 400 turbulence either increased or decreased simulated heads from their laminar elevations specifically head differences from laminar elevations ranged from about 18 to 27 cm and were explained by the magnitude of net flow to the finite difference model cell turbulence also affected the sensitivities of model parameters specifically the composite scaled sensitivities of horizontal hydraulic conductivities decreased by as much as 70 when turbulence was essentially removed these hydraulic head and sensitivity differences due to turbulent groundwater flow highlight potential errors in models based on the equivalent porous media assumption which assumes laminar flow in uniformly distributed void spaces