Conductivity Of Aquifer Research Articles

つくば市周辺地域における三次元水文地質モデルの構築と帯水層の透水性の推定への適用

Three-dimensional earth sciences information is being made available in digital formats because such information is useful and understandable to various users. In this study, we develop a three-dimensional hydrogeological model of Tsukuba City and the surrounding region, and develop a method for estimating the hydraulic conductivity of aquifers in combination with the three-dimensional hydrogeological model and other related hydrogeological information with the primary objective of proposing a method for evaluating groundwater resources. The three-dimensional hydrogeological model was developed using a geological map and drilling data with data interpolated using a geostatistical method. The model developed reproduced the data used well, and it was found to be accurate for practical use. Moreover, this model could be used for various types of visualization, from which information could be extracted and applied immediately to numerical simulations; this provided information that was useful and understandable for evaluating groundwater resources. The proposed method for estimating the hydraulic conductivity of aquifers was developed from hydraulic conductivities obtained from various drilling surveys, which were grouped together taking geology and stratigraphy into consideration based on a three-dimensional hydrogeological model, and using a statistical analysis. This method can be used to rapidly evaluate trends in hydraulic conductivity by integrating data distributed over a broad area. In addition, if a columnar section of an evaluated point is obtained, this method can be used to determine the actual hydraulic conductivity of aquifers. Therefore, these methods were found to be effective for evaluating groundwater resources.

토양.지하수오염원 관리우선순위 개략평가기법 개발

This study developed preliminary assessment methodology for priority listing of soil and groundwater contamination sources, considering source characteristics, local environments and risk receptors. Source characteristics were evaluated by scoring relative risk of contamination sources. Local environments were evaluated by scoring annual rainfall, hydraulic conductivity of aquifer, and annual groundwater use. Risk receptors were evaluated by scoring local population, direct distance to surface water, direct distance to drinking-water wells. Scores of each parameter were allocated by analysing distribution of parameter values obtained from government databases. Distributed scores of source characteristics local environments: risk receptors were 12 : 12 : 12. The preliminary assessment scored 0 to 36 for each soil and groundwater sources. Inventory of soil and groundwater sources consisted of 7 categories. This study applied the preliminary assessment methodology to Manan-Gu, Anyang City, Korea. The number of car repair and washing facility was the largest in the contamination source inventory. Petroleum storage facilities showed the highest assessment score. The preliminary assessment methodology also indicated that Anyang-Dong was the priority section among Anyang-Dong, Suksu-Dong, Bakdal-Dong. This study is the first trial for relative ranking soil and groundwater contamination sources by considering source and local characteristics. Therefore, further researches and revision of the preliminary assessment methodology need to be pursued for various applications.

An Assessment of the Huntley (2000) Baildown Tests Data Analysis Method

Introduction Oil baildown tests are routinely conducted in practice for determining oil conductivity in aquifers. The commonly used approach, in practice, is to adapt the existing slug test data analysis methods even though there are more sophisticated approaches based on numerical models (e.g., Zhu et al. 1993). Unfortunately, there are some controversial issues in applying especially the existing slug test data analysis methods to drawdown data for oils in aquifers and these are the main reasons for this commentary. Over 10 years ago, Huntley (2000) published a method under the title “Analytic Determination of Hydrocarbon Transmissivity from Baildown Tests.” This method is also included in the American Petroleum Institute (API) Interactive Guide (2002, Version 2.0, Release 2.04) based on Beckett and Lyverse (2002). Huntley presents his method mainly by applying the Bouwer and Rice (1976) slug test data analysis method with some modification to oil baildown tests by including a density correction factor. The same API Interactive Guide also includes the Lundy and Zimmerman Method (Lundy 2002), which is also based on the same modification on the Bouwer and Rice (1976) slug test data analysis method (Lundy 2002). Most importantly, the Lundy and Zimmerman method does not use a density correction factor as the case is for the Huntley method. The Bouwer and Rice slug test data analysis method is based on the Thiem equation (Thiem 1906), which predicts the drawdown in a confined aquifer under steady-state conditions. Therefore, the aforementioned modification by Huntley, and Lundy and Zimmerman imply that, in reality, the Thiem equation is modified.

Interpretation of the piezometric fluctuations and precursors associated with the November 29, 2007, magnitude 7.4 earthquake in Martinique (Lesser Antilles)

On November 29, 2007, a 7.4 earthquake occurred near the volcanic island of Martinique (French West Indies). It was widely felt in the Caribbean. Piezometric level changes correlated with the earthquake were recorded by 12 of the 24 piezometers in the groundwater monitoring network. A methodology has been developed for the interpretation of long-duration piezometric anomalies. It enables us to demonstrate that the hydraulic conductivity increased at the scale of the whole aquifer, by an order of magnitude of 5 to 10%, as a consequence of the earthquake. With this methodology, it is possible to compute either the aquifer hydraulic conductivity increase during the earthquake or its hydrodynamic parameters: diffusivity and relative location of the piezometer along a flow line. It shows, for instance, that the amplitude of the piezometric change due to the earthquake is not directly related to its intensity, but rather to the structure and hydrodynamic properties of the aquifer and also to the location of the piezometer. It also proves that a piezometric increase due to an earthquake cannot be straightforwardly related to a decrease in the hydraulic conductivity of the aquifer. Consequently, in such an active geodynamical context, tectonic processes appear to be among the factors responsible of the magnitude of the hydraulic conductivity of shallow aquifers. Piezometric precursors of the earthquake were definitely observed, but the operational use of such signals is, as yet, far from obvious.

Evaluation of hydrogeochemical processes in the Pleistocene aquifers of Middle Ganga Plain, Uttar Pradesh, India

Evaluation of major ion chemistry and solute acquisition process controlling water chemical composition were studied by collecting a total of fifty-one groundwater samples in shallow ( 25 m) in the Varanasi area. Hydrochemical facies, Mg-HCO3 dominated in the largest part of shallow groundwater followed by Na-HCO3 and Ca-HCO3 whereas Ca-HCO3 is dominated in deep groundwater followed by Mg-HCO3 and Na-HCO3. High As concentration (>50 μg/l) is found in some of the villages situated in northeastern parts (i.e. adjacent to the concave part of the meandering Ganga river) of the Varanasi area. Arsenic contamination is confined mostly in tube wells (hand pump) within the Holocene newer alluvium deposits, whereas older alluvial aquifers are having arsenic free groundwater. Geochemical modeling using WATEQ4F enabled prediction of saturation state of minerals and indicated dissolution and precipitation reactions occurring in groundwater. Majority of shallow and deep groundwater samples of the study area are oversaturated with carbonate bearing minerals and under-saturated with respect to sulfur and amorphous silica bearing minerals. Sluggish hydraulic conductivity in shallow aquifer results in higher mineralization of groundwater than in deep aquifer. But the major processes in deep aquifer are leakage of shallow aquifer followed by dominant ion-exchange and weathering of silicate minerals.

Calibration of spatial aquitard distribution using hydraulic head changes and regularisation

Irregularly expressed aquitards have a significant impact on hydraulics and redox conditions. The method expands the scope and applicability of characterising spatial structures close to well fields. The test site is an aquifer system with two aquifers divided by an aquitard (glacial till), located at a well field for drinking water abstraction. During operation, the wells are frequently switched and hydraulic head data are recorded at 10 wells in both aquifers. The data contain information about the impact of each abstraction well on each observation well. We develop an inverse modelling procedure to calibrate spatial aquifer parameters from this data. Instead of heads we calibrate to selected head differences to keep the model concise to short term fluctuations and to reduce data. The calibrated model parameters are storativity of the upper aquifer, hydraulic conductivity of both aquifers and leakage of the aquitard. The calibration is carried out spatially by pilot points with the software PEST using regularisation. Different cross validations show that the leakage can be calibrated in a physically meaningful way, but not the hydraulic conductivities and not the storativity. Geostatistic assumptions are not required. The calibrated spatial aquitard distribution coincides with bore profiles and explains anomalies of redox conditions.

Unconfined Aquifer Permeability near hand-dug Wells in the Coastal and Interior dryland of the Libertador General Bernardo O'Higgins Region, Chile

In the dryland of the Libertador General Bernardo O?Higgins Region in Chile, most farmers rely on wide and shallow hand-dug wells as their primary source of water during the dry summer. Few of these wells have sufficient yield for more than domestic use (human consumption, livestock, and irrigation of a subsistence garden). To more accurately assess available groundwater resources, saturated hydraulic conductivity (K) of aquifers in the eight counties that comprise this region?s dryland was estimated using evacuation and recovery tests in 353 hand-dug wells. K followed a log-normal distribution and ranged over nearly five orders of magnitude. County median K varied by a factor of 5 and a slight increasing K trend in the southward direction. In one northern county, less than 4% of the sites had K > 4 m d-1. In the t two southernmost counties, approximately one-quarter of the K values exceeded 4 m d-1. This is approximately the minimum K required for a typical well (1 m diameter and 3 m depth below the water table) to yield 1 L s-1 of water, which is roughly the yield required to irrigate 1 ha. Aquifers located where parent material was predominantly intrusive granite had slightly higher and statistically significant K than those formed predominantly of metamorphic and sedimentary rock. A semi-variogram of K provided weak evidence of a characteristic length scale of approximately 4 km.

Electrical conductivity as an indicator of iron reduction rates in abiotic and biotic systems

Although changes in bulk electrical conductivity (σb) in aquifers have been attributed to microbial activity, σb has never been used to infer biogeochemical reaction rates quantitatively. To explore the use of electrical conductivity to measure reaction rates, we conducted iron oxide reduction experiments of increasing biological complexity. To quantify reaction rates, we propose composite reactions that incorporate the stoichiometry of five different types of reactions: redox, acid‐base, sorption, dissolution/precipitation, and biosynthesis. In batch experiments and the early stages of a column experiment, such reaction stoichiometries inferred from a few chemical measurements allowed quantification of the Fe oxide reduction rate based on changes in electrical conductivity. The relationship between electrical conductivity and fluid chemistry did not hold during the latter stages of the column experiment when σb increased while fluid chemistry remained constant. Growth of an electrically conductive biofilm could possibly explain this late stage σb increase. The measured σb increase is consistent with a model proposed by analogy from percolation theory that attributes the increased conductivity to growth of biofilms with conductivity of ∼5.5 S m−1 in at least 3% of the column pore space. This work demonstrates that measurements of σb and flow rate, combined with a few direct chemical measurements, can be used to quantify biogeochemical reaction rates in controlled laboratory situations and may be able to detect the presence of biofilms. This approach may help in designing future field experiments to interpret biogeochemical reactivity from conductivity measurements.

Evolution of hydraulic conductivity in the floodplain of a meandering river due to hyporheic transport of fine materials

[1] The hydraulic conductivity of riverbeds and shallow aquifers controls hyporheic flow and surface water-groundwater exchange, which is critical to aquatic systems. We show that the hydraulic conductivity of shallow alluvial aquifers subject to sinuosity-driven hyporheic flow is dynamic because of transport of fine materials. We analyze changes in hydraulic conductivity over one year at a meander-scale experimental river-aquifer system using water table monitoring, repeat in-situ hydraulic tests, grain size analysis, and flow modeling with particle tracking. Areas with relatively high initial hydraulic conductivity became more permeable after one year, while areas with lower initial hydraulic conductivity became less permeable. Particle tracking suggests fine materials were flushed from the more permeable portions of the aquifer and deposited in the less permeable areas down-gradient. Since hydraulic conductivity evolution has feedback on flow, static or synoptic hydraulic conductivity measurements in river-hyporheic-riparian systems may need to be revisited. Temporally changing hydraulic conductivity has the capacity to impact rates of ecological and biogeochemical processes.

A Bayesian approach for inverse modeling, data assimilation, and conditional simulation of spatial random fields

This paper addresses the inverse problem in spatially variable fields such as hydraulic conductivity in groundwater aquifers or rainfall intensity in hydrology. Common to all these problems is the existence of a complex pattern of spatial variability of the target variables and observations, the multiple sources of data available for characterizing the fields, the complex relations between the observed and target variables and the multiple scales and frequencies of the observations. The method of anchored distributions (MAD) that we propose here is a general Bayesian method of inverse modeling of spatial random fields that addresses this complexity. The central elements of MAD are a modular classification of all relevant data and a new concept called “anchors.” Data types are classified by the way they relate to the target variable, as either local or nonlocal and as either direct or indirect. Anchors are devices for localization of data: they are used to convert nonlocal, indirect data into local distributions of the target variables. The target of the inversion is the derivation of the joint distribution of the anchors and structural parameters, conditional to all measurements, regardless of scale or frequency of measurement. The structural parameters describe large‐scale trends of the target variable fields, whereas the anchors capture local inhomogeneities. Following inversion, the joint distribution of anchors and structural parameters is used for generating random fields of the target variable(s) that are conditioned on the nonlocal, indirect data through their anchor representation. We demonstrate MAD through a detailed case study that assimilates point measurements of the conductivity with head measurements from natural gradient flow. The resulting statistical distributions of the parameters are non‐Gaussian. Similarly, the moments of the estimates of the hydraulic head are non‐Gaussian. We provide an extended discussion of MAD vis à vis other inversion methods, including maximum likelihood and maximum a posteriori with an emphasis on the differences between MAD and the pilot points method.

General Steady-State Shape Factor for a Partially Penetrating Well

We present the closed form of a general steady-state shape factor for a partially penetrating well in a uniform anisotropic aquifer. Our simple analytical expression for the shape factor has a uniform representation for full range of parameters and meets or exceeds the accuracy of previous results obtained through semiempirical methods (e.g., Bouwer and Rice [1976] equations). This general shape factor pertains to the flow of fluids (water or air) in subsurface formations when the upper formation boundary has constant potential and the lower boundary is impermeable. The results of our investigation are directly applicable to analyses of (1) slug tests with falling or rising head and (2) injection/extraction tests with constant head, essential techniques for the characterization of hydraulic conductivity of aquifers, streambeds, or lakebeds as well as the design of aquifer and soil remediation systems.

Analytical solutions for the flow fields near funnel‐and‐gate reactive barriers with hydraulic losses

Permeable reactive barriers (PRBs) are a passive in situ technology that is based on the interception and physical, chemical, and/or biological remediation of a contaminant plume through installation of reactive material in an aquifer. The present work is an extension and generalization of a previous paper and derives analytical expressions for flow fields toward PRBs in two dimensions on the basis of the conformal mapping approach. Considered is the classic funnel‐and‐gate configuration with perpendicular funnel arms (PFGs) as well as PRBs with velocity equalization walls. While the aquifer is assumed to be homogeneous in a uniform far field, the hydraulic conductivity of the reactive material is allowed to take arbitrary values above or below the aquifer conductivity. At the up‐ and down‐gradient interfaces between reactor and aquifer, highly permeable gravel packs are assumed to establish constant head conditions. The flow fields are analyzed regarding the widths and shapes of respective capture zones as functions of PRB type and dimensions, reactor hydraulic resistance (including flow divergence and longevity), and ambient groundwater flow direction. Expressions for discharge fields are developed as needed for particle‐tracking algorithms. Charts of relative capture width are given to facilitate PRB design and may be included in more comprehensive PRB design/optimization approaches. An efficient approach is presented to estimate reactor conductivity and capture flow from monitoring the hydraulic loss at the reactor. Inherent assumptions and results are validated against numerical flow field solutions and water level field data for the PFG PRB at the Moffett Federal Airfield, California.

Assessing the accuracy of monitoring wells in tidal wetlands

Groundwater movement in marshes is driven by tidal fluctuations, evapotranspiration, and the infiltration of rainwater. These forcings act on time scales of several hours. Monitoring wells in marshes must, therefore, be able to react rapidly and accurately to changes in these forcings. To assess the response characteristics of a given well design, I define a well's time constant as the square of its radius divided by the product of the aquifer conductivity and the length of its screen. Using numerical simulations, I show that the logarithm of the mean deviation over a tidal cycle between the head in the well and the head in the adjoining undisturbed aquifer is linearly related to the logarithm of the well time constant. Similar logarithmic relationships occur for the maximum deviations on flood and ebb tides and the well time constant. Thus, wells in soils with low hydraulic conductivity must have smaller radii and longer screens than those in more conductive soils in order to have similar accuracy. Alternatively, the time constant can be lowered by incorporating the pressure sensor in a slug that displaces most of the water above the sensor and thereby greatly reduces the volume of water that must move between the well and the aquifer.

Biased Monitoring of Fresh Water‐Salt Water Mixing Zone in Coastal Aquifers

In coastal aquifers, significant vertical hydraulic gradients are formed where fresh water and underlying salt water discharge together upward to the seafloor. Monitoring boreholes may act as "short circuits" along these vertical gradients, connecting between the higher and the lower hydraulic head zones. When a sea tide is introduced, the fluctuations of both the water table and the depth of the mixing zone are also biased due to this effect. This problem is intensified in places of long-screen monitoring boreholes, which are common in many places in the world. For example, all approximately 500 boreholes of the fresh water-salt water mixing zone in the coastal aquifer of Israel are installed with 10 to 50 m long screens. We present field measurements of these fluctuations, along with a three-dimensional numerical model. We find that the in-well fluctuation magnitude of the mixing zone is an order of magnitude larger than that in the porous media of the actual aquifer. The primary parameters that affect the magnitude of this bias are the anisotropy of the aquifer conductivity and the borehole hydraulic parameters. With no sea tide, borehole interference is higher for the anisotropic case because the vertical hydraulic gradients are high. When tides are introduced, the amplitude of the mixing zone fluctuation is higher for the isotropic case because the overall effective hydraulic conductivity is greater than the conductivity in the anisotropic case. In the aquifer, the fresh water-salt water mixing zone fluctuations are dampened, and tens of meters inland from the shoreline, the fluctuations are on the order of few centimeters.

Modelling karst geomorphology on different time scales

The evolution and flow in a karst aquifer is studied with numerical simulations, based on the KARST model ( Karst Aquife R Simulation Tool). The aquifer consists of a three-dimensional interconnected network of conduits representing fractures in the rock, and a porous rock matrix representing the finer fissured system in the rock. Flow through the aquifer can be driven by both diffuse recharge from precipitation and localised sinking streams, and the aquifer drains towards a large karst resurgence representing the base level. Superimposed onto the karst aquifer is a landscape, which can evolve with time by small-scale diffusive processes, large-scale river erosion, and karst denudation. Fractures in the aquifer are enlarged with time by chemical dissolution, enhancing the secondary porosity of the karst aquifer. The enlargement of fractures results in a dramatic increase of the aquifer conductivity over several orders of magnitude, and a change of flow patterns from an initially pore-controlled to a heterogeneous fracture-controlled aquifer. During the evolution, the water table is falling from an initially high position close to the land surface to a lower level coinciding with the actual base level. Two model scenarios are studied to elucidate the karst aquifer evolution in three dimensions. The evolution models are then complemented by event-type spring discharge modelling, which can be used as a predictive tool for karst spring discharge and contaminant transport.

Estimation of hard rock aquifers hydraulic conductivity from geoelectrical measurements: A theoretical development with field application

Summary Based on the analogy between Darcy’s law for groundwater flow and Ohm’s law for electric current flow, a methodology has been developed to estimate the hydraulic conductivity and transmissivity of hard rock granite aquifer from geoelectrical parameters. The common parameter, aquifer thickness (t), has been used to combine the two relations and form an analytical equation. Mathematical relation shows a negative correlation between hydraulic conductivity and aquifer resistivity, and a positive correlation between transmissivity and longitudinal conductance. The methodology has been calibrated and validated in hard rock granite aquifers in India. The good agreement between aquifer hydraulic conductivity (K) and transmissivity (T) obtained from the resistivity sounding parameters and those obtained from pumping test analysis proves the potentiality of the methodology. It has been applied to estimate the K and T from the surface electrical resistivity parameters and results were utilized to prepare the K and T maps of Maheshwaram watershed in hard rock terrain in India.

Semi-analytical solution for flow in a leaky unconfined aquifer toward a partially penetrating pumping well

Summary A semi-analytical solution is presented for the problem of flow in a system consisting of unconfined and confined aquifers, separated by an aquitard. The unconfined aquifer is pumped continuously at a constant rate from a well of infinitesimal radius that partially penetrates its saturated thickness. The solution is termed semi-analytical because the exact solution obtained in double Laplace‐Hankel transform space is inverted numerically. The solution presented here is more general than similar solutions obtained for confined aquifer flow as we do not adopt the assumption of unidirectional flow in the confined aquifer (typically assumed to be horizontal) and the aquitard (typically assumed to be vertical). Model predicted results show significant departure from the solution that does not take into account the effect of leakage even for cases where aquitard hydraulic conductivities are two orders of magnitude smaller than those of the aquifers. The results show low sensitivity to changes in radial hydraulic conductivities for aquitards that are two or more orders of magnitude smaller than those of the aquifers, in conformity to findings of earlier workers that radial flow in aquitards may be neglected under such conditions. Hence, for cases were aquitard hydraulic conductivities are two or more orders of magnitude smaller than aquifer conductivities, the simpler models that restrict flow to the radial direction in aquifers and to the vertical direction in aquitards may be sufficient. However, the model developed here can be used to model flow in aquifer‐aquitard systems where radial flow is significant in aquitards. a 2008 Elsevier B.V. All rights reserved.

Three-dimensional groundwater flow to a shallow pond: An explicit solution

Summary Steady groundwater flow near a shallow disk-shaped pond, the bottom of which is in direct hydraulic contact with a confined homogeneous aquifer, is studied analytically by the Fabrikant method of L-operators. For the case of a unidirectional flow at infinity a rigorous and explicit expression for the hydraulic head and specific discharge components are obtained. Depending on the ambient specific discharge, aquifer conductivity, pond radius, and the pond bottom head three regimes (gaining, losing and flow-through) of pond water–groundwater interaction are explicitly demarcated. The hinge line on the pond bottom for the flow-through regime is shown to be a straight line. The only stagnation point in the gaining regime is found from a simple nonlinear equation. Closed-form expressions for the total pond seepage rate and inflow-, outflow-rates are presented. Streamlines and isochrones of groundwater travel time are found by a particle-tracking method. The capture and release zones of the pond are outlined.

Erratum/

GroundwaterVolume 45, Issue 2 p. 125-125 Free Access Erratum/ This article corrects the following: A Simple Constant-Head Injection Test for Streambed Hydraulic Conductivity Estimation M. Bayani Cardenas, Vitaly A. Zlotnik, Volume 41Issue 6Groundwater pages: 867-871 First Published online: December 13, 2005 First published: 29 January 2007 https://doi.org/10.1111/j.1745-6584.2006.00283.xAboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat In the Technical Note “A simple constant-head injection test for streambed hydraulic conductivity estimation,” M.B. Cardenas and V.A. Zlotnik (2003) presented a constant-head injection test (CHIT) method for mapping hydraulic conductivity of unconsolidated streambed sediments. There is a typographical error (namely, a misplaced parenthesis) in their equation (11) that could lead to erroneous values for the shape factor P . Equation (11) should read: (11) where A and B are coefficients originally defined by Bouwer and Rice (1976), b is the aquifer saturated thickness below the stream, l is the depth to the top of the screen from the stream-aquifer interface, L is the screen length and rw is the piezometer radius. Note that b in the natural logarithm of the second term in the right-hand side of the equation is also divided by rw. Not doing so not only results in incorrect values for P but may also result in negative arguments for the terms in the brackets leading to complex values after taking the natural logarithm. In general, this error does not change conclusions in the original note or the applicability of the CHIT method. We thank Charles F. Pitz of the Washington State Department of Ecology for bringing this error to our attention. References Bouwer, H., and R.C. Rice. 1976. A slug test for determining hydraulic conductivity of unconfined aquifers with completely of partially penetrating wells. Water Resources Research 12, no. 3: 423– 428. Wiley Online LibraryWeb of Science®Google Scholar Cardenas, M.B., and V.A. Zlotnik. 2003. A simple constant-head injection test for streambed hydraulic conductivity estimation. Ground Water 41, no. 6: 867– 871. Wiley Online LibraryCASPubMedWeb of Science®Google Scholar Volume45, Issue2March–April 2007Pages 125-125 ReferencesRelatedInformation

A new model (DRARCH) for assessing groundwater vulnerability to arsenic contamination at basin scale: a case study in Taiyuan basin, northern China

A modified DRASTIC model for groundwater vulnerability assessment (abbreviated as DRARCH model by combining the first letters of its six assessment indices) was proposed. It is essentially the specific application of DRASTIC model rather than a new model. Both natural hydrogeological conditions that prevent groundwater from contamination and important intrinsic hydrogeochemical properties of sediments in vadose zone that are related to the retardation of contaminants were considered as vulnerability indices. The DRARCH model consists of six indices: (1) Depth to the water table, (2) net Recharge, (3) Aquifer thickness, (4) Ratio of cumulative thickness of clay layers to total thickness of vadose zone, (5) Contaminant adsorption coefficient of sediment in vadose zone, and (6) Hydraulic conductivity of aquifer. The rating values and the weights of these vulnerability indices were obtained by contaminant transport simulation and factor analysis method respectively. Furthermore, the DRARCH model was applied to evaluate the groundwater vulnerability to arsenic contamination in Taiyuan basin, northern China, where groundwaters with high arsenic concentration occur in some localities. GIS-based mapping of groundwater vulnerability using this model indicates that the distribution of very high and high-vulnerability areas corresponds well to that of high-arsenic groundwaters. The DRARCH model is therefore reliable and useful for guiding groundwater environment management.