Estimation Of Hydraulic Parameters Research Articles

Field and Laboratory Hydraulic Characterization of Landslide‐Prone Soils in the Oregon Coast Range and Implications for Hydrologic Simulation

Core Ideas Laboratory hydraulic parameters differ substantially from values estimated from field data. Hydraulic parameters determined in the laboratory overestimate hysteresis magnitude. Field data‐based model parameterizations may simulate landslide initiation more accurately.Unsaturated zone flow processes are an important focus of landslide hazard estimation. Differences in soil hydraulic behavior between wetting and drying conditions (i.e., hydraulic hysteresis) may be important in landslide triggering. Hydraulic hysteresis can complicate soil hydraulic parameter estimates and impact prediction capability. This investigation focused on hydraulic property estimation for soil in a landslide‐prone area where the relative importance of hysteresis is unclear. Laboratory measurements of soil‐water retention from field soils in the Oregon Coast Range during wetting and drying show that pronounced hydraulic hysteresis is present. In contrast, a 4‐yr field data record of pore‐water pressure and soil‐water content from multiple soil pits at the same landslide‐prone area shows relatively minor hydraulic hysteresis compared with the laboratory estimates. Simulated subsurface hydrologic response parameterized using estimates from field data more closely matched hydrologic observations relative to model parameterization based on laboratory analysis of repacked soil samples. Our results suggest that (i) unsaturated hydraulic parameter estimates based on in situ field data, as opposed to laboratory measurements alone, may lead to more accurate simulation of the hydrologic response to rainfall, (ii) in situ data of soil‐water retention may need to include values at both high suctions and near saturation to improve estimates of soil hydraulic parameters for slope failure applications, and (iii) laboratory measurements of soil‐water retention made under dynamic conditions may overestimate hydraulic hysteresis.

Inverse Estimation of Soil Hydraulic and Transport Parameters of Layered Soils from Water Stable Isotope and Lysimeter Data

Core Ideas To determine the water retention curve from inverse modeling, θ and ψ need to be monitored. δ18O ratios contained information to inversely estimate soil hydraulic parameters. Different observation types should be combined in a single OF to estimate parameters. Averages of local measurement could be described using effective parameters. Accurate measurement of fluxes at lysimeter boundaries improved model parameterization. Accurate estimates of soil hydraulic parameters and dispersivities are crucial to simulate water flow and solute transport in terrestrial systems, particularly in the vadose zone. However, parameters obtained from inverse modeling can be ambiguous when identifying multiple parameters simultaneously and when boundary conditions are not well known. Here, we performed an inverse modeling study in which we estimated soil hydraulic parameters and dispersivities of layered soils from soil water content, matric potential, and stable water isotope (δ18O) measurements in weighable lysimeter systems. We used different optimization strategies to investigate which observation types are necessary for simultaneously estimating soil hydraulic and solute transport parameters. Combining water content, matric potential, and tracer (e.g., δ18O) data in one objective function (OF) was found to be the best strategy for estimating parameters that can simulate all observed water flow and solute transport variables. A sequential optimization, in which first an OF with only water flow variables and subsequently an OF with transport variables was optimized, performed slightly worse indicating that transport variables contained additional information for estimating soil hydraulic parameters. Hydraulic parameters that were obtained from optimizing OFs that used either water contents or matric potential could not predict non‐measured water flow variables. When a bromide (Br−) tracer experiment was simulated using the optimized parameters, the arrival time of the bromide pulse was underestimated. This suggested that Br− sorbed onto clay minerals and amorphous oxides under the prevailing geochemical conditions with low pH values. When accounting for anion adsorption in the simulation, Br− concentrations were well predicted, which validated the dispersivity parameterization.

Hydrogeological and Hydrochemical Assessment of Basin Granitoids in Assin and Breman Districts of Ghana

Hydrogeological and hydrochemical assessments were carried out in Assin and Breman districts of Ghana. A multi-criteria approach was used in the assessment of the basin granitoids including; electrical resistivity survey, pumping test and water quality analysis. A total of twenty-five (25) representative boreholes were drilled, developed and pumped; obtaining data for aquifer hydraulic parameters estimation. Correlation analysis was used to determine relationships that exist between aquifer hydraulic parameters. Schoeller, Piper, Stiff plot and Gibbs diagrams were used to determine the hydrogeochemical facies, water types and the mechanism that control groundwater quality. The statistical analysis determined that aquifer hydraulic parameters discharge rate (Q), hydraulic conductivity (K) and Transmissivity (T) showed a strong positive correlation with specific capacity (Q/Sw) with R value 0.8462, 0.8738 and 0.8332 respectively. The K and T were respectively between 0.02 - 0.90 m/day and 0.36 - 13.47 m2/day with mean of 0.24 m/day and 3.03 m2/day respectively. The K values indicate a hydrogeological condition of aquiclude with relatively low permeability and medium water bearing capacity. The aquifer T magnitude is very low to low, groundwater potential is adequate for local water supply with limited and private consumption. All physicochemical parameters were within the permissible limits of Ghana Standards Authority (GSA) and World Health Organisation (WHO) except for apparent colour, pH, Fe and Mn. Distribution of major ions in groundwater samples was calculated and the general trend among cations and anions was found to be Ca2+ > Na+ > Mg2+ and Cl− > HCO3− > SO42− respectively. The study area shows five main water types namely; Ca-HCO3, Na-Mg-HCO3-SO4, Ca-SO4, Na-Cl and Mg-Na-Cl. Weathering of rock-forming minerals as the mechanism controlling the groundwater chemistry. Microbiological parameters were above the permissible limits. Groundwater is suitable for drinking after treatment with chlorination, aeration and slow sand filtration methods.

Sequential reduction of slope stability uncertainty based on temporal hydraulic measurements via the ensemble Kalman filter

A data assimilation framework, utilising measurements of pore water pressure to sequentially improve the estimation of soil hydraulic parameters and, in turn, the prediction of slope stability, is proposed. Its effectiveness is demonstrated for an idealised numerical example involving the spatial variability of saturated hydraulic conductivity, ksat. It is shown that the estimation of ksat generally improves with more measurement points. The degree of spatial correlation of ksat influences the improvement in the predicted performance, as does the selection of initial input statistics. However, the results are robust with respect to moderate uncertainty in the spatial and point statistics.

Evaluation of a cosmic-ray neutron sensor network for improved land surface model prediction

Abstract. In situ soil moisture sensors provide highly accurate but very local soil moisture measurements, while remotely sensed soil moisture is strongly affected by vegetation and surface roughness. In contrast, cosmic-ray neutron sensors (CRNSs) allow highly accurate soil moisture estimation on the field scale which could be valuable to improve land surface model predictions. In this study, the potential of a network of CRNSs installed in the 2354 km2 Rur catchment (Germany) for estimating soil hydraulic parameters and improving soil moisture states was tested. Data measured by the CRNSs were assimilated with the local ensemble transform Kalman filter in the Community Land Model version 4.5. Data of four, eight and nine CRNSs were assimilated for the years 2011 and 2012 (with and without soil hydraulic parameter estimation), followed by a verification year 2013 without data assimilation. This was done using (i) a regional high-resolution soil map, (ii) the FAO soil map and (iii) an erroneous, biased soil map as input information for the simulations. For the regional soil map, soil moisture characterization was only improved in the assimilation period but not in the verification period. For the FAO soil map and the biased soil map, soil moisture predictions improved strongly to a root mean square error of 0.03 cm3 cm−3 for the assimilation period and 0.05 cm3 cm−3 for the evaluation period. Improvements were limited by the measurement error of CRNSs (0.03 cm3 cm−3). The positive results obtained with data assimilation of nine CRNSs were confirmed by the jackknife experiments with four and eight CRNSs used for assimilation. The results demonstrate that assimilated data of a CRNS network can improve the characterization of soil moisture content on the catchment scale by updating spatially distributed soil hydraulic parameters of a land surface model.

A Flexible System for Estimation of Infiltration and Hydraulic Resistance Parameters in Surface Irrigation

Abstract. Characterizing the infiltration and hydraulic resistance process is critical to the use of modeling tools for the hydraulic analysis of surface irrigation systems. Because those processes are still not well understood, various formulations are currently used to represent them. A software component has been developed for estimation of the parameters of infiltration and hydraulic resistance models. Infiltration computations rely on volume balance analysis. The software provides flexibility for defining the estimation problem with various data configurations. The procedure works with various infiltration and resistance formulations. Given the inherent inaccuracies of volume balance analysis, the software provides tools for identifying and correcting some of those inaccuracies. Computational tests are provided to illustrate the capabilities and limitations of the proposed procedures. Keywords: Basin irrigation, Border irrigation, Computer model, Computer software, Furrow irrigation, Model calibration, Surface irrigation, Water management, WinSRFR.

Estimation of Infiltration and Hydraulic Resistance in Furrow Irrigation, with Infiltration Dependent on Flow Depth

Abstract. Estimation of infiltration and hydraulic resistance model parameters from furrow irrigation evaluation data was investigated. A semi-physical, flow-depth dependent furrow infiltration model was used for the analysis. Macropore infiltration was modeled empirically as a constant volume of water per unit area that is absorbed instantaneously. The estimated infiltration parameters were the saturated hydraulic conductivity and the macropore constant. Hydraulic resistance was modeled with the Manning equation; thus, the estimated resistance parameter was the Manning coefficient. The estimation procedure uses volume balance calculations and unsteady flow simulation. Estimation of the flow-depth dependent infiltration parameters requires first the estimation of an empirical infiltration function, via volume balance, and of the resistance parameter, via unsteady flow simulation. Simulated flow depth hydrographs as a function of distance are then used as inputs for a second set of volume balance calculations with the semi-physical infiltration model. This procedure takes advantage of the fact that similar surface flow conditions (advance and recession times, flow depths, and runoff rate) can be predicted with different infiltration functions. The procedure was tested with two irrigation data sets, each consisting of three furrows. With both data sets, the semi-physical infiltration model fitted the measured volume balance data as well as empirical infiltration models. For each group of furrows, estimates of the hydraulic conductivity were of comparable magnitude and were consistent with published values for the particular soil texture. Likewise, estimates of the macroporosity parameter were consistent for each group of furrows. Estimates of the Manning coefficient suggest very uniform hydraulic resistance. Finally, results show that the effect of flow-depth dependent infiltration on irrigation distribution uniformity depends on soil and hydraulic conditions. For one of the data sets, distribution uniformity computed with the proposed infiltration model was only slightly different from the uniformity computed assuming that infiltration depends only on opportunity time, because of the large macropore flow contribution and the shallow flow conditions. Keywords: Distribution uniformity, Furrows, Green-Ampt, Hydraulic conductivity, Hydraulic modeling, Hydraulic resistance, Infiltration, Inverse modeling, Irrigation, Parameter estimation.

Estimating hydraulic parameters for the complex hydrodynamic models

Hydrodynamic models have usually been calibrated manually, by trial-and-error, with different values of hydraulic parameters and hydraulic characteristics of boundary conditions. This method of calibration and estimation of hydraulic parameters requires an extensive knowledge and experience of experts, but whether the resulting solution includes an optimal set of parameters still remains an open question. An optimization method founded upon the Gauss-Marquardt-Levenberg algorithm, along with PEST software based on that algorithm, introduces automation of model calibration with regularization, which substantially reduces the effect of expert judgment on the result. The method also introduces the so-called 'pilot points', which transcend the concept of homogeneous zones with the values of hydraulic parameters of a hydrogeological system or zones with the specified boundary conditions. Mineral ore deposits are the most complex in geological and hydrogeological terms, so the lignite coal mine 'Tamnava - West Field' was selected as a good area to test the approach. Applying the proposed method, the spatial distributions of the horizontal (Kx=Ky) and vertical (Kz) components of hydraulic conductivity are determined in the study area.

The limiting factor relationship between geoelectric and hydraulic parameters – a case study

The limiting factor relationship between geoelectric and hydraulic parameters of parts of the West Chad Basin, northeastern Nigeria was appraised in this present study. The objectives of study included the estimation of the aquifer hydraulic parameters of the Pleistocene aged alluvium Formation from both the geoelectric and pumping test datasets with a view to determining empirical and limiting factor relationships and groundwater conditions. 106 geoelectric sounding and seventeen pumping test datasets were analyzed with RESIST Software and time – drawdown plots respectively. The concept of Dar-Zarrouk parameters was used to determine aquifer hydraulic parameters. The range of values from results included the following; derived transmissivity Tc (188.9-2789.8 m2/day) with Tc mean of 1540.84 m2/day; and field pumping transmissivity T (113.2 - 1436.6 m2/day with Tmean of 634.96 m2/day and derived hydraulic conductivity Kc values of 11.12-189.73 m/day, field pumping hydraulic conductivity K of 6.67- 101.31 m/day with the Kc mean of 115.34 m/day; Kmean of 36.22 m/day respectively. A linear fit relationship between the two datasets showed a correlation coefficient of 0.52861, standard deviation of 310.81. Higher values obtained from the geoelectric derived hydraulic parameters in few borehole sites in multiple of two or three suggested a limiting factor of the method. It may, therefore, be concluded that the limiting factor may have arisen from overestimation of the aquifer thickness occasioned by the degree of saturation and/or sand to clay ratio to which geoelectrical resistivity method might have responded. Hence, the method remained a tool on the choice of prospective high yielding borehole site selection from the consideration of the findings.Keywords: Aquifer, hydraulic, geoelectric, pumping, transmissivity, saturation

Optimization of a New Inverse Method for Estimation of Individual Soil Hydraulic Parameters under Field Conditions

In this research, the EISHP (Estimation of Individual Soil Hydraulic Parameters) model was developed for estimation of the individual soil hydraulic parameters of van Genuchten‘s equation (α, n, Ks, θs, and θr). This model was used to predict soil water content and pressure head at different soil depths by implicitly solving the Richards equation, applying the finite difference method. In this model, the objective function (OF) was computed by summation of squared differences between measured and estimated soil water content and pressure head up to ten days after wetting of soil columns. In the EISHP model, each parameter was optimized separately by achieving the minimum value of OF using the Newton-Raphson method and keeping the remaining parameters constant. The optimized parameter value was then used in optimizing the other parameters. Iteration was continued until the difference between the two computational steps of OF was negligibly small and a unique value had been estimated for each parameter. The main contribution of this research is presentation of a methodology for the optimization of individual parameters, which guarantees the uniqueness of parameter values. In contrast, simultaneous optimization of the entire parameter set would not necessarily lead to unique values.

A comprehensive numerical analysis of the hydraulic behavior of a permeable pavement

The increasing frequency of flooding events in urban catchments related to an increase in impervious surfaces highlights the inadequacy of traditional urban drainage systems. Low Impact Development (LID) techniques have proven to be a viable and effective alternative by reducing stormwater runoff and increasing the infiltration and evapotranspiration capacity of urban areas. However, the lack of adequate modeling tools represents a barrier in designing and constructing such systems. This paper investigates the suitability of a mechanistic model, HYDRUS-1D, to correctly describe the hydraulic behavior of permeable pavement installed at the University of Calabria. Two different scenarios of describing the hydraulic behavior of the permeable pavement system were analyzed: the first one uses a single-porosity model for all layers of the permeable pavement; the second one uses a dual-porosity model for the base and sub-base layers. Measured and modeled month-long hydrographs were compared using the Nash-Sutcliffe efficiency (NSE) index. A Global Sensitivity Analysis (GSA) followed by a Monte Carlo filtering highlighted the influence of the wear layer on the hydraulic behavior of the pavement and identified the ranges of parameters generating behavioral solutions. Reduced ranges were then used in the calibration procedure conducted with the metaheuristic Particle swarm optimization (PSO) algorithm for the estimation of hydraulic parameters. The best fit value for the first scenario was NSE=0.43; for the second scenario, it was NSE=0.81, indicating that the dual-porosity approach is more appropriate for describing the variably-saturated flow in the base and sub-base layers. Estimated parameters were validated using an independent, month-long set of measurements, resulting in NSE values of 0.43 and 0.86 for the first and second scenarios, respectively. The improvement in correspondence between measured and modeled hydrographs confirmed the reliability of the combination of GSA and PSO in dealing with highly dimensional optimization problems. Obtained results have demonstrated that PSO, due to its easiness of implementation and effectiveness, can represent a new and viable alternative to traditional optimization algorithms for the inverse estimation of unsaturated hydraulic properties. Finally, the results confirmed the suitability and the accuracy of HYDRUS-1D in correctly describing the hydraulic behavior of permeable pavements.

Investigation of hydraulic parameters of a weathered mylonite fault from field pumping tests: A case study

This paper presents a case history where the hydraulic parameters of a weathered mylonite fault located in the way of shield tunneling for the Xie-Zhong section on Metro Line No. 7 in Guangzhou City were determined using a series of field pumping tests. The weathered mylonite fault contains fissure groundwater, which would result in a high potential of water ingress during shield tunneling within the weathered mylonite strata. Therefore, the first stage of pumping tests involving five pumping wells was initially carried out. To verify the validity of the hydraulic parameters derived, the second stage of pumping tests involving four pumping wells was carried out. In addition, both an analytical method that involves a well-flow calculation for a fissure-confined aquifer for non-orthogonal anisotropic rock mass and a numerical simulation based on the theory of the equivalent continuum porous media were used to derive the hydraulic parameters based on the field pumping test data. The analytical method can provide the values of hydraulic conductivity only in the horizontal plane and is not able to capture the hydraulic characteristics of standalone stratum of the multi-aquifer system. In the numerical model, the weathered mylonite fault due to the nature of non-uniform mylonite strata distribution is further divided into four sub-regions with different hydraulic conductivities, according to the calculated influence radius of groundwater drawdown or geological formation. This leads to estimates of hydraulic parameters that are closer to real values, and enhances our understanding of non-uniform fissure development.

Modeling cross-hole slug tests in an unconfined aquifer

A modified version of a published slug test model for unconfined aquifers is applied to cross-hole slug test data collected in field tests conducted at the Widen site in Switzerland. The model accounts for water-table effects using the linearized kinematic condition. The model also accounts for inertial effects in source and observation wells. The primary objective of this work is to demonstrate applicability of this semi-analytical model to multi-well and multi-level pneumatic slug tests. The pneumatic perturbation was applied at discrete intervals in a source well and monitored at discrete vertical intervals in observation wells. The source and observation well pairs were separated by distances of up to 4m. The analysis yielded vertical profiles of hydraulic conductivity, specific storage, and specific yield at observation well locations. The hydraulic parameter estimates are compared to results from prior pumping and single-well slug tests conducted at the site, as well as to estimates from particle size analyses of sediment collected from boreholes during well installation. The results are in general agreement with results from prior tests and are indicative of a sand and gravel aquifer. Sensitivity analysis show that model identification of specific yield is strongest at late-time. However, the usefulness of late-time data is limited due to the low signal-to-noise ratios.

Simple methods for quick determination of aquifer parameters using slug tests

The slug test is still one of the simplest and cost-effective methods to interpret the hydraulic parameters for aquifer analysis. This study introduces two new estimation approaches for the slug test, the time shift method (TSM) and arc-length matching method (AMM), to identify aquifer parameters in a reliable and accurate manner, which was established on the idea that any change in the normalized drawdown or arc-length measurements of the data curve at the predefined drawdown levels is linked with the variation of storativity. These approaches remove the need for superimposition of the type curves and the field data. The proposed methods are straightforward to apply and automatize the parameter estimation process. TSM and AMM were tested with a number of numerical experiments including synthetically generated data augmented with random noise, hypothetical slug tests conducted in a heterogeneous rock-fracture system, and well-known real field data. The skin effect was also implemented to evaluate its impact on the estimation performance of the suggested approaches. The results verified that both proposed methods are able to produce estimates of hydraulic parameters more accurately than existing methods. The proposed methods could serve as a viable supplementary interpretation tool for slug test analysis.

Different scenarios for inverse estimation of soil hydraulic parameters from double-ring infiltrometer data using HYDRUS-2D/3D

AbstractIn this study, HYDRUS-2D/3D was used to simulate ponded infiltration through double-ring infiltrometers into a hypothetical loamy soil profile. Twelve scenarios of inverse modelling (divided into three groups) were considered for estimation of Mualem-van Genuchten hydraulic parameters. In the first group, simulation was carried out solely using cumulative infiltration data. In the second group, cumulative infiltration data plus water content ath= −330 cm (field capacity) were used as inputs. In the third group, cumulative infiltration data plus water contents ath= −330 cm (field capacity) andh= −15 000 cm (permanent wilting point) were used simultaneously as predictors. The results showed that numerical inverse modelling of the double-ring infiltrometer data provided a reliable alternative method for determining soil hydraulic parameters. The results also indicated that by reducing the number of hydraulic parameters involved in the optimization process, the simulation error is reduced. The best one in infiltration simulation which parametersα,n, andKswere optimized using the infiltration data and field capacity as inputs. Including field capacity as additional data was important for better optimization/definition of soil hydraulic functions, but using field capacity and permanent wilting point simultaneously as additional data increased the simulation error.

Forward Coupled Modeling and Assessment of Gravity Anomalies Caused by Pumping Tests in Unconfined Aquifers Under Unsteady-State Conditions

Analysis of drawdown data from pumping tests is the most common method for identification of aquifer properties and estimation of hydraulic parameters in hydrogeology. Limited hard hydraulic data from wells, expensive and intrusive, can be supplemented with geophysical spatially distributed information. Gravity, sensible to mass variations, can provide information about hydraulic parameters and storage coefficients of aquifers. A satisfactory use of gravity requires the computation of temporal evolution of gravity anomalies related with the dynamic hydraulic process. For simplified and ideal problems, the calculation can be accomplished with analytical solutions. However, the limitations of analytical solutions in capturing some relevant characteristics, like heterogeneities, that require the use of numerical models, are well known. This article shows how the time-dependent gravity anomaly caused by a pumping test can be calculated in a unique code, in a coupled manner and in a single run. The methodology avoids the use and transference of data between various codes and can be utilized in a coupled hydrogeophysical inversion procedure. Additionally, it is flexible enough to include a wide range of characteristics that can be encountered in any pumping test, and is an adequate framework for field survey planning via analysis and study of time-dependent gravity curves.

An exact explicit solution for one-dimensional, transient, nonlinear Richards’ equation for modeling infiltration with special hydraulic functions

Summary This work develops a simple exact and explicit solution of the one-dimensional transient and nonlinear Richards’ equation for soils in a special case of exponential water retention curve and power law hydraulic conductivity. The exact solution is obtained as traveling wave based on the approach proposed by Philip (1957, 1967) and adopted by Zlotnik et al. (2007). The obtained solution is novel, and it expresses explicitly the water content as function of the depth and time. It can be useful to model infiltration into semi-infinite soils with time-dependent boundary conditions and infiltration with constant boundary condition but space-dependent initial condition. A complete analytical inverse procedure based on the proposed analytical solution is presented which allows the estimation of hydraulic parameters. The proposed exact solution is also important for the verification of numerical schemes as well as for checking the implementation of time-dependent boundary conditions.

The dependence of induced polarization on fluid salinity and pH, studied with an extended model of membrane polarization

The estimation of hydraulic parameters from spectral induced polarization (SIP) measurements is difficult partly because the electrical impedance of sediments depends on several parameters that are not related to the texture. Important parameters that influence the spectral response are fluid salinity and pH. In order to understand the behaviour of SIP spectra from a mechanistic point of view, we carry out simulations with a membrane polarization model. The geometry consists of a sequence of wide and narrow pores with finite radii. The charge distribution at the mineral surface is described by a triple layer model, characterized by the zeta potential and the partition coefficient. We extended an existing model by incorporating known dependencies of the zeta potential and the partition coefficient on fluid salinity and pH.Our simulation results predict a decrease of the maximum phase shift of the complex electrical conductivity with increasing salinity, consistent with experimental observations. For very small pore radii, the phase shift may also show the opposite behaviour and increase with salinity. The imaginary conductivity at 1Hz increases with increasing salinity, followed by a peak and a decrease at high salinities. The fact that our model predicts a decrease of the imaginary conductivity at high salinities is particularly important, because strong experimental evidence was recently found for such a decrease, which was theoretically unexplained so far.Both the maximum phase shift and the imaginary conductivity at 1Hz decrease when pH decreases. The reason is that at low pH, the zeta potential and the partition coefficient both decrease, corresponding to a smaller charge density at the mineral surface, resulting in a weaker impact of the electrical double layer. The few existing experimental studies on pH dependence are qualitatively consistent with our simulation results.

Hydraulic parameters estimation by using an approach based on vertical electrical soundings (VES) in the semi-arid Khanasser valley region, Syria

A new alternative approach based on using Vertical electrical sounding (VES) technique is proposed for computing the hydraulic conductivity K of an aquifer. The approach takes only the salinity of the groundwater into consideration. VES measurements in the locations, where available water samples exist, are required in such an approach, in order to calibrate and establish empirical relationships between transverse resistance Dar-Zarrouck TR parameter and modified transverse resistance MTR, and between MTR and transmissivity T. Those relationships are thereafter used to extrapolate the transmissivity even in the VES points where no water samples exist. This approach is tested and practiced in the Khanasser valley, Northern Syria, where the hydraulic conductivity of the Quaternary aquifer is computed. An acceptable agreement is found between the hydraulic conductivity values obtained by the proposed approach and those obtained by the pumping test which range between 0.864 and 8.64 m/day (10−5 and 10−4 m/s). The Quaternary aquifer transmissivity of the Khanasser Valley, has been characterized by using this approach and by adapting the MTR parameter. The transmissivity varies between a minimum of 79 m2/day and a maximum of 814 m2/day, with an average of 283 m2/day and a standard deviation of 145 m2/day. The easy and inexpensive approach proposed in this paper can be applied in other semi arid regions.

An overview of groundwater chemistry studies in Malaysia.

In this paper, numerous studies on groundwater in Malaysia were reviewed with the aim of evaluating past trends and the current status for discerning the sustainability of the water resources in the country. It was found that most of the previous groundwater studies (44%) focused on the islands and mostly concentrated on qualitative assessment with more emphasis being placed on seawater intrusion studies. This was then followed by inland-based studies, with Selangor state leading the studies which reflected the current water challenges facing the state. From a methodological perspective, geophysics, graphical methods, and statistical analysis are the dominant techniques (38, 25, and 25%) respectively. The geophysical methods especially the 2D resistivity method cut across many subjects such as seawater intrusion studies, quantitative assessment, and hydraulic parameters estimation. The statistical techniques used include multivariate statistical analysis techniques and ANOVA among others, most of which are quality related studies using major ions, in situ parameters, and heavy metals. Conversely, numerical techniques like MODFLOW were somewhat less admired which is likely due to their complexity in nature and high data demand. This work will facilitate researchers in identifying the specific areas which need improvement and focus, while, at the same time, provide policymakers and managers with an executive summary and knowledge of the current situation in groundwater studies and where more work needs to be done for sustainable development.