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Borehole geophysical logging of four production wells completed in Precambrian metagranite in Fauquier County, Virginia (USA), was conducted to characterize stratigraphy, collect water-bearing fracture orientations and describe vertical hydraulic gradients in the vicinity of each borehole. Long-term (48–90 h) single-well pump test data were reevaluated for each well to better characterize this locally important aquifer system. Single-well aquifer test analyses indicate mid-to-late-time infinite acting radial flow conditions within the fractured rock aquifer, followed by increasing late-time contribution of stored groundwater from recharge boundaries. Later-time pump test results are believed to indicate that water-bearing fractures within the metagranite are ultimately recharged by groundwater stored within the regolith. Assumptions about the presence of a recharge boundary sourced by the regolith were tested with a simple groundwater flow model that was calibrated to observed drawdown data associated with one of the long-term pump tests. This study identifies fracturing associated with shear-related metamorphic fabrics in the wellbore and demonstrates the significance of these fractures as mechanisms for accessing groundwater. Results from this investigation indicate that shear-related metamorphic fabrics can be important structures for integrating transmissive fracture networks within the Marshall Metagranite and possibly within other Blue Ridge basement rocks possessing similar metamorphic history.

Sustained pumping of groundwater can lead to declining water levels in wellfields and concerns regarding the sustainability of groundwater resources. Aquifer Storage and Recovery (ASR) is a promising approach for maintaining water levels in wells and increasing the sustainability of groundwater resources. Herein, an analytical model relying on superposition of the Theis equation is used to resolve water levels at 40 wells in three vertically stacked ASR wellfields operating in the Denver Basin Aquifers, Colorado (USA). Fifteen years of dynamic recovery/recharge data are used to estimate aquifer and well properties, which are then used to predict water levels at individual wells. Close agreement between modeled and observed water levels supports the validity of the analytical model for ASR wellfield applications. During the study period, 45 million m3 of groundwater is produced and 11 million m3 is recharged, leading to a net withdrawal of 34 million m3 of groundwater. To quantify the benefits of recharge, the analytical model is applied to predict water levels at wells absent the historical recharge. Results indicate that during recovery and no-flow periods, recharge has increased water levels at wells up to 60 m compared to the no-recharge scenario. On average, the recharge increased water levels during the study period by 3, 4, and 11 m for wells in the Denver, Arapahoe, and Laramie Fox-Hills Aquifers, respectively. This study demonstrates the utility of analytical modeling to quantify the effects of long-term ASR at wells.

This paper deals with water pumping cost minimization, in a confined infinite aquifer, proposing an alternate pulsed pumping schedule. The transient flow analysis is conducted for two wells with equal pumping rates. Specifically, two pumping schedules are analytically compared. In the first case, well users pump simultaneously, and in the second one they cooperate so that they pump alternately. This paper proves that the proposed alternate pumping schedule works as a stabilizer, reducing the high hydraulic drawdowns values, regardless of the aquifer characteristics. Moreover, pumping alternately is better in terms of pumping cost, compared to simultaneous pumping, though benefit become negligible as distance between wells becomes large. Two simplified equations are proposed, one to find the difference of the hydraulic drawdowns between the two pumping schedules and the other one to find the economic benefit of each well from cooperation. The equations are finally applied to a number of cases and their results are compared to the results obtained from an algorithm created to calculate the hydraulic drawdowns and the pumping cost, using the Theis equation. The results can be very useful in irrigation scheduling, as they can be applied to systems of well users/farmers, to reduce pumping cost.

We developed a method to estimate aquifer transmissivity from the hydraulic-head data associated with the normal cyclic operation of a water supply well thus avoiding the need for interrupting the water supply associated with a traditional aquifer test. The method is based on an analytical solution that relates the aquifer's transmissivity to the standard deviation of the hydraulic-head fluctuations in one or more observation wells that are due to the periodic pumping of the production well. We analyzed the resulting analytical solution and demonstrated that when the observation wells are located near the pumping well, the solution has a simple, Dupuit like form. Numerical analysis demonstrates that the analytical solution can also be used for a quasi-periodic pumping of the supply well. Simulation of cyclic pumping in a statistically heterogeneous medium confirms that the method is suitable for analyzing the transmissivity of weakly or moderately heterogeneous aquifers. If only one observation well is available, and the shift in the phase of hydraulic-head oscillations between the pumping well and the observation well is not identifiable. Prior knowledge of aquifer's hydraulic diffusivity is required to obtain the value of the aquifer transmissivity.

Made available in DSpace on 2022-05-01T10:18:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-01 Fundação para o Desenvolvimento da UNESP (FUNDUNESP) The sensitivity of the derivative analysis to the variation of flow rates allows it to solve ambiguities, provide diagnostics of the flow dimension, and identify the boundary conditions of the tested aquifer. Based on the results of a derivative analysis, it was hypothesized that the set of assumptions for the fitted solution to the drawdown curve are valid for the tested aquifer. Thus, combining the derivative analysis results and the detailed geological characterization, a new approach was developed to build preliminary conceptual hydrogeological models in cases where field data are scarce. Applying this approach, it was concluded that basaltic aquifers in the Serra Geral Aquifer System (SGAS) are comprised of leaky confined aquifers, which the alternation of basalt floods that have permeable horizons at the top and with low permeability of interior flow. The simulated drawdown curve in a transient flow model perfectly matched with the drawdown curve recorded in the field, thus supporting the suitability of the built conceptual model. This statement challenges the prevailing theory that conceptualizes SGAS as a fractured aquifer. Conclusively, the current approach is capable of producing suitable conceptual models in cases of field data scarcity. Future investigations in other complex geological contexts may validate the present approach. Center for Environmental Studies (CEA) São Paulo State University UNESP Basin Studies Laboratory São Paulo State University UNESP Department of Applied Geology São Paulo State University UNESP Center for Environmental Studies (CEA) São Paulo State University UNESP Basin Studies Laboratory São Paulo State University UNESP Department of Applied Geology São Paulo State University UNESP

Uncertainty quantification of groundwater (GW) aquifer parameters is critical for efficient management and sustainable extraction of GW resources. These uncertainties are introduced by the data, model, and prior information on the parameters. Here we develop a Bayesian inversion framework that uses Interferometric Synthetic Aperture Radar (InSAR) surface deformation data to infer the laterally heterogeneous permeability of a transient linear poroelastic model of a confined GW aquifer. The Bayesian solution of this inverse problem takes the form of a posterior probability density of the permeability. Exploring this posterior using classical Markov chain Monte Carlo (MCMC) methods is computationally prohibitive due to the large dimension of the discretized permeability field and the expense of solving the poroelastic forward problem. However, in many partial differential equation (PDE)-based Bayesian inversion problems, the data are only informative in a few directions in parameter space. For the poroelasticity problem, we prove this property theoretically for a one-dimensional problem and demonstrate it numerically for a three-dimensional aquifer model. We design a generalized preconditioned Crank--Nicolson (gpCN) MCMC method that exploits this intrinsic low dimensionality by using a low-rank based Laplace approximation of the posterior as a proposal, which we build scalably. The feasibility of our approach is demonstrated through a real GW aquifer test in Nevada. The inherently two dimensional nature of InSAR surface deformation data informs a sufficient number of modes of the permeability field to allow detection of major structures within the aquifer, significantly reducing the uncertainty in the pressure and the displacement quantities of interest.

Sustainable groundwater management plans are of critical importance to the future of increasingly scarce water resources. Borehole magnetic resonance (BMR) is a wireline logging technique used to provide in-situ formation evaluation. BMR can be utilised to monitor BMR responds to both the volumes of fluids present in a rock, and the geometry of the pores in which this water resides. As such, it is a powerful addition to any borehole geophysical characterisation aimed at evaluating the storage and flow capacity of subsurface formation or aquifer. BMR is highly advantageous due to its ability to provide a lithology independent measurement of formation porosity. A further application of BMR is to estimate the formation permeability. Semi-empirical models have been developed which quantify the relationship between the pore size distribution captured using BMR and formation permeability. The parameters which are used within these models are formation dependent. Thus, the parameters must be calibrated to the geology of interest to ensure that the BMR permeability model is tuned to provide appropriate permeability estimates. Historically this has been through coring programs, however this is often not available in a hydrogeological context due ability to retrieve core in unconsolidated formations. This paper reviews a process that uses a combination of packer tests, pump tests and lugeon tests to calibrate the coefficients to calculate hydraulic conductivity from a T2 distribution. The process will be discussed and its applications to set of data will be presented., Open-Access Online Publication: March 03, 2023

The Theis equation is an important mathematical model used for analyzing drawdown data obtained from pumping tests to estimate aquifer parameters. Since the Theis model is a nonlinear equation, a complex graphical procedure is employed for fitting this equation to pump test data. This graphical method was originally proposed by Theis in the late 1930s, and since then, all the groundwater textbooks have included this fitting method. Over the past 90 years, every groundwater hydrologist has been trained to use this tedious procedure for estimating the values of aquifer transmissivity (T) and storage coefficient (S). Unfortunately, this mechanical procedure does not provide any intuition for understanding the inherent limitations in this manual fitting procedure. Furthermore, it does not provide an estimate for the parameter error. In this study, we employ the public domain coding platform Python to develop a script, namely, PyTheis, which can be used to simultaneously evaluate T and S values, and the error associated with these two parameters. We solve nine test problems to demonstrate the robustness of the Python script. The test problems include several published case studies that use real field data. Our tests show that the proposed Python script can efficiently solve a variety of pump test problems. The code can also be easily adapted to solve other hydrological problems that require nonlinear curve fitting routines.

Faults can act as flow barriers or conduits to groundwater flow by introducing heterogeneity in permeability. We examine the hydrogeology of the Sandwich Fault Zone, a 137 km long zone of high-angle faults in northern Illinois, using a large-scale historic aquifer test. The fault zone is poorly understood at depth due to the majority of the faults being buried by glacial deposits and its near-vertical orientation which limits geologic sampling across faults. The aquifer test-perhaps one of the largest in terms of overall withdrawal in North American history-was conducted in 1942 at a facility adjacent to the fault zone. More than 34,000 m3 /day was pumped for 37 days from nine multiaquifer wells open to the stratified Cambrian-Ordovician sandstone aquifer system. We modeled the aquifer test using a transient MODFLOW-USG model and simulated pumping wells with the CLN package. We tested numerous fault core/damage zone conceptualizations and calibrated to drawdown values recorded at production and observation wells. Our analysis indicates that the fault zone is a low-permeability feature that inhibits lateral movement of groundwater and that there is at least an order of magnitude decrease in horizontal hydraulic conductivity in the fault core compared to the undeformed sandstone. Large head declines have occurred north of the fault zone (over 300 m since predevelopment conditions) and modifying fault zone parameters significantly affects calibration to regional drawdown on a decadal scale. The flow-barrier behavior of the fault zone has important implications for future groundwater availability in this highly stressed region.

Over the past decades, a new aquifer test technology (sequential pumping tests or hydraulic tomography, HT) has been developed and successfully applied to many field sites to delineate the spatial distributions of hydraulic properties (e.g., transmissivity (T) and storage coefficient (S)). Yet, the reproducibility of its estimated T and S fields and the predictive capabilities of the estimates for different flow scenarios at different time periods remain unexplored. That is to say, if the estimated fields based on sequential pumping tests conducted during different years are the same since the geologic formation and processes may have undergone changes. In order to answer this important question, this study first compares the drawdown-time behaviors from the sequential pumping tests (SPTs) conducted in 2010 with those conducted in 2012 at a field site and then finds they are similar but different in detail. It then uses these data to estimate the T and S fields and checks the reproducibility of the estimates. The estimated heterogeneity patterns are found to be generally reproducible in spite of uncertainties. In addition, the estimates from each year are capable of predicting the observed drawdowns, induced by independent pumping tests during the corresponding year (i.e., self-validation). Moreover, the estimated fields are cross-validated. That is, this study uses the estimates obtained from the 2010 pumping tests to predict the observed drawdowns of the independent pumping tests conducted in 2012. Likewise, it uses the estimates from 2012 pumping tests to forecast the drawdowns of the independent pumping tests of 2010. The results of both self-validation and cross-validation indicate that the estimated T and S fields based on the test in one year can be used to predict bulk flow behavior in the other year. Differences in detailed behaviors may be attributed to changes in the processes, omitted in the depth-averaged flow model.

Movement of fluid particles about historic subsurface releases and through well fields is often governed by dynamic subsurface water levels. Motivations for tracking the movement of fluid particles include tracking the fate of subsurface contaminants and resolving the fate of water stored in subsurface aquifers. Based on superposition of the Theis solution in both space and time, this research explores an analytical solution based on the Theis equation using dynamic pumping well data to resolve how fluid particles move around wells under dynamic pumping conditions. The results provide relatively uniform capture zones for a pumping well. Further, the results show that even under continuous pumping and injection conditions, groundwater will not flow far from the well. Accordingly, groundwater positions can be evaluated based on the research for dynamic pumping. Using the assumptions proposed by the Theis solution, the analytical solution developed in this study provides a simple method to evaluate particle movement in wells used to both store and recover water.

This paper presents a comprehensive hydrogeological investigation that involves field work, aquifer test, hydrogeochemical analysis, environmental isotope analysis, and interpretations around a proposed nuclear power facility in South Africa. The study was undertaken to test the complementarity of the various methods in the coastal aquifer and to verify the hydrogeological conditions within and around the site. The study revealed the presence of two types of aquifers: an upper primary aquifer made up of the Cenozoic deposits of the Algoa Group, and a deeper fractured aquifer made of the Palaezoic Table Mountain Group (TMG) metasedimentary rocks. Owing to ductile deformation in the form of folding, the fractured quartzite and shale aquifers resulted in an artesian condition, often characterized by slightly acidic (pH &le, 6) and iron-rich groundwater. The most important hydrogeochemical processes responsible for the observed changes in the hydrochemical composition and facies are mineral dissolution, ion exchange and mixing. The environmental isotope results suggest that all groundwater samples are characterized by a depleted &delta, 18O and &delta, 2H signal, indicating high latitude moisture source (southern polar region) and recharge from rainfall, with no or minimal evaporation before and during infiltration. Similarities in the stable isotope signatures between the deeper and shallow aquifer confirm the presence of a strong hydraulic link. The residence time of groundwater in the aquifers underlying the proposed nuclear power plant is estimated using tritium (3H) and 14C, and the results indicate that in the shallow aquifer it ranges from recent recharge to 50 years, and in the deeper aquifer, it ranges from 430 &plusmn, 5 years to 1000 &plusmn, 10 years, which exists in a quasi-pristine condition.

The complex nature of the Ethiopian aquifer requires detail, characterization, and analysis. Consequently, characterization of groundwater flow and major aquifer systems was conducted in the upper left bank of the Jemma River catchment in the Blue Nile Basin. The research area covered 1255 km2. The main objective of the research was to characterize the aquifer systems and groundwater flow dynamics of the area. The software applied during the research work were aquifer test, ArcMap 10.2, global mapper 17, AutoCAD, Exelis ENVI, geomatics, and rockworks. Pumping test data and spring discharge together with qualitative field description were used to classify the aquifer system. Accordingly, the different aquifer classes are fissured aquifer developed on basalts on the plateau (moderate to low groundwater potential), mixed aquifer (high permeability and very high productivity), fissured aquifer developed on basalts in the valleys (high permeability and low to moderate storage), porous and fissured sandstone aquifer in deep valleys, and localized aquifer with intergranular porosity and permeability (high permeability and high productivity). From the analysis of water level measurements of boreholes, hand-dug wells, and springs, the groundwater flow system is controlled by surface morphology and lineaments. Therefore, the groundwater flows from SE and S-SSE corner towards the N and NW corner of the catchment. Understanding groundwater dynamics and characterizing the aquifer in the catchment are very crucial which in turn help to manage the available water resource for domestic, industrial, and agricultural purpose. Besides, the research will be used to manage aquifers from depletion.

Diante do avanço das simulações de águas subterrâneas nos últimos anos como forma de propor soluções para gestão de recursos hídricos, a presente pesquisa teve como objetivo a elaboração de um modelo hidrogeológico conceitual para o aquífero freático da Unidade 3 da Univiçosa, em que foi analisado o rebaixamento do nível de água do lençol freático através dos dados de bombeamento dos poços existentes no local e obtidos os parâmetros hidrodinâmicos do aquífero através do software Aquifer Test. Também foram realizadas análises potenciométricas dos poços bem como a relação entre a precipitação e a recarga do aquífero por intermédio de campanhas de monitoramento dos níveis de água estático e dinâmico dos poços e do regime de precipitação da região no intuito de se compreender o comportamento do lençol freático da região. Foi verificado que houve diferentes respostas ao bombeamento para os poços denominados “Frente Esquerda” e “Fundos Direita”, este último devido a um pequeno lago em sua proximidade. Durante a recuperação ambos os poços se comportaram de maneira semelhante em que os níveis de água atingiram valores acima dos medidos antes dos testes de bombeamento, porém com o poço “Fundos Direita” atingindo valores muito acima, por volta de 1,75 m a mais do que o nível medido antes do teste de bombeamento. Os valores dos parâmetros hidrodinâmicos encontrados foram: Transmissividade (T) 1,0 x 10-3 m2/s, Condutividade Hidráulica (K) 4,17 x 10-5 m/s e Armazenamento (S) 1,0 x 10-4. Estes valores permitiram a obtenção do Raio de influência dos poços sendo possível constatar a não sobreposição dos cones de rebaixamento entre os poços “Frente Esquerda” e “Fundos Direita”. A análise potenciométrica permitiu verificar o comportamento do fluxo de água entre os poços, incluindo um terceiro denominado “Residencial”, sendo constatado que em regime estacionário a água flui dos poços de maior para os de menor cota altimétrica e em regime transitório, quando há bombeamento, ela flui em direção aos poços. A análise da relação entre a precipitação e a recarga do aquífero não foi significativa, mostrando pequenas variações nos níveis estáticos da água dos poços em períodos chuvosos, o que leva a crer que a quantidade de água precipitada e o período de monitoramento não foram suficientes para constatar alterações nos níveis de água do lençol freático. Por fim, foi constatado que a explotação de água dos poços não compromete a quantidade de água no local, visto que não há interferência entre eles, porém recomenda-se a execução de sondagens nas proximidades dos poços para melhor caracterização dos mesmos e ampliação do período de monitoramento para melhor conhecimento do comportamento do aquífero freático local por meio da elaboração de um modelo hidrogeológico matemático.

This study offers a reinterpretation of archive aquifer tests, predominantly on the basis of recovery data, from an original datasheet of thermal water wells located in carbonate and sandstone aquifer units in the vicinity of Budapest, Hungary. The study compares the hydraulic conductivity (K) and specific storage (Ss) values derived in the first instance from an aquifer test evaluation. This included an initial application of the classical analytical Cooper and Jacob method. Subsequently, the visual two-zone (VTZ) numerical method was applied, then third, a more complex model, namely, WT software. It was found that the simple analytical solution is not able to represent the field conditions accurately, while in the course of the application of the VTZ model, it proved possible to alter the various hydraulic parameters within reasonable limits to fit the field data. In the case of the VTZ model, the researcher is required to calculate the accuracy of the fitted model separately, while with the WT model, this is automatic, the software seeks out the best fit. In addition to VTZ parameters, the WT model can efficiently incorporate data on up to 500 model layers, water level, and pressure. The optimization of the parameters may be achieved by automatic calibration, improving the accuracy of the numerical results. Recovery tests for 12 wells were numerically simulated to obtain values for vertical and horizontal hydraulic conductivity and specific storage for Triassic and Eocene fractured carbonate and the Upper-Miocene-Pliocene granular sandstone aquifer units. When an analytical solution is applied, only average values could be obtained. The conclusion reached was that the results of the analytical solution can be improved by the use of numerical methods. These methods are able to incorporate basic information on well design, aquifer material and the hydrogeological environment in the course of the evaluation. The revision of the archive recovery data using numerical methods may assist in the quest for better data for numerical flow and transport simulations without the need to perform new tests. In addition, the methods employed here can explain cases in which the original analytical interpretations proved unable to yield reliable data and predictions.

Straightforward solutions have long been expected for the analysis of multiwell aquifer tests. In this paper, we derive series analytical solutions of steady-state groundwater flow in a rectangular-shaped aquifer with pumping/injection wells for both confined and unconfined conditions. Double Fourier Transform (DFT) technique is applied to deal with different combinations of impermeable and specified head boundaries on sides. The obtained solutions are compact and concise in mathematics and flexible in terms of well number, well locations, and pumping/injection rates. Hatoucaidang, a groundwater resource field in the Ordos Plateau, Northwestern China, is introduced as a field case study, where a multiwell aquifer test was conducted. One of the analytical solutions derived herein is used to estimate hydraulic conductivities by applying a direct calculation method and a least square estimation method regarding observed versus calculated drawdowns. By comparing with nearby single-well pumping tests, the reliability of the derived analytical solutions is proven. This study facilitates utilizing the multiwell aquifer test to analyze the general behavior of groundwater movement in aquifer systems.

The North West urban growth corridor (NWGC) is an important area accommodating Perth’s expanding population which is expected to increase by 50% to 3.5 million by 2050. Groundwater from a shallow Quaternary aquifer is the preferred source for the reticulated water supply provided by the Water Corporation (WC). Due to rising demands, the Department of Water and Environmental Regulation (DWER) reviewed groundwater allocations in the area to provide increased security for environmental values related to wetlands and to manage the saltwater interface. Because of inadequacies in the regional numerical model in the NWGC area, DWER developed a spread sheet analytical model to calculate groundwater balances and discharge to the ocean. This assessment proposed lower allocations for users than derived by the model. After consultations with DWER, WC developed an analytical assessment using additional data and an alternative method. Instead of individual aquifer test results, the regional impacts of significant extraction from a wellfield over 15 years were used to develop a relationship between the aquifer’s response to pumping and transmissivity. This resulted in a larger estimate of throughflow which was more consistent with the original modelled estimates. These results were also confirmed by recently acquired drilling and aquifer testing data in the area.

The hydraulic parameters representative of actual aquifer conditions can be obtained through aquifer tests formerly known as pumping tests. Diverse methodologies based on analytical or numerical solutions have been proposed for the interpretation of aquifer tests; however, measurement and model errors are often neglected, which could lead to hydraulic parameter values that do not reflect the aquifer conditions. In this paper, a new alternative is presented for the interpretation of aquifer tests in confined aquifers based on the Cooper–Jacob solution by means of the dynamic Kalman filter and a nonlinear optimization method. This proposal was tested in two previously published case studies; the measured drawdowns were filtered by considering measurement and model errors to match the Cooper–Jacob solution. For the case studies, the results show that filtering the measured drawdowns leads to variations of up to 49.97% in the values for T and 150% for S when compared to the values determined by methodologies that neglect measurement and model errors. A poor match between filtered and measured data reflects large measurement errors and considerable deviations of the aquifer conditions with respect to the proposed model.

The Theis solution is perhaps the most influential and frequently used analytical model in groundwater hydrology. Its publication in 1935 led to immediate and continued use for simulating hydraulic head drawdown, in both confined and unconfined aquifers, as a tool in aquifer parameter estimation. For educational purposes, the Theis solution and the related Jacob’s approximation often serve as the backbone for teaching pumping-well theory, including topics such as boundary conditions in aquifers, image well theory, linear superposition, and pumping-induced streamflow depletion. Clearly, a thorough understanding of the Theis solution is critical for groundwater engineers and hydrologists. However, the solution often is presented as a “black box”, neglecting the actual origins of its derivation and accompanying physical context. This can lead to misconceptions about the model and its inherent limitations. In this paper, a physically based detailed derivation of the Theis solution is presented, along with a method of calculating drawdown from a pumping well without resorting to the final Theis equation. Examples of both constant-rate pumping and variable-rate pumping are presented and compared to results using the original Theis solution. In particular, variable pumping rates are accounted for by direct numerical integration of an earlier form in the original Theis derivation, removing the need for linear superposition of solutions in time. In this way, it is hoped the paper will provide a method of calculation that ties the model user to the physical meaning of the solution, including its assumptions.

Characterization the different volcanic rock aquifers and evaluation of their respective productivity was done in Kola Diba well field (221 km2), north-central Ethiopia. Collections and analyses of pertinent secondary data were followed by detailed field investigation. Geological and structural investigations was conducted in the field paying particular attention to the different features of the overlying sediments and underlying volcanic rocks units that made them to be a water bearing formations. The structural data were analyzed using Stereonet v7.3 software. Hydrogeological logs, Semi‐log scale (specialized plot) and Log‐Log scale (diagnostic plot) were prepared to determine the different aquifer types and also to characterize the nature of each aquifer. Inventory of groundwater structures (boreholes and hand dug wells) were also conducted as part of hydrogeological investigation. Pumping test data were collected from ten deep wells and were analyzed using Theis and Neuman methods using Aquifer Test v3.5 software. Stratigraphically, the geology of the area from bottom to top is aphanitic basalt, porphyritic basalt and alluvial sediments. The rocks are affected by different degree of weathering and fractures. The geological formations of the area are categorized hydrogeologically into intergranular and fractured medium and fracture medium. The major aquifers are confined, unconfined and leaky. Hydraulic conductivity values of these different aquifers ranges from 0.0048 to 1.46 m/day with mean of 0.444 m/day, transmissivity ranges from 0.5 to 474 m2/day and specific capacity ranges from 0.026 to 0.88 l/sec/m with mean values of 86.878 m2/day and 0.325 88 l/sec/m, respectively. On the basis of their corresponding transmissivity and specific capacity value, the different aquifers of the studied area were categorized into four aquifer potentiality groups: moderate to low, low to weak, weak and very weak aquifers potentiality. Any future development of groundwater should be focused on the moderate to low potentiality aquifers.

Groundwater fluctuation usually reflects the property of aquifer in nature. Actually, water level change can be caused not only by barometric pressure changes resulted from atmospheric motion, but also by the tidal effect from nearby marine system or water body. In confined aquifer, an increase in barometric pressure usually will cause a decrease in water level in well to an amount described by the barometric efficiency. The barometric efficiency can be also used as a correction factor to remove barometric effects on water levels in wells during an aquifer test. With the rise of the tidal sea on the coastal aquifer, it indicates that there will be compensating increases of water pressure and stress in the skeleton of aquifer. External forcing on groundwater level in the coastal aquifer, such as barometric effect and tidal sea, usually affect the water level to fluctuate with different phases to some extent. An adaptive adjustment to remove the combination of barometric and oceanic tidal efficiency is presented in this study. This research suggests that the presented formula can simultaneously identify the individual efficiency for barometric effect and load of tidal sea considering their combined observation of groundwater level in aquifer system. An innovative application has been demonstrated for the deep aquifers adjacent to the West Pacific Ocean.

Limestone aquifers are of great interest as a drinking water resource in many countries. They often have a complex crushed and fractured geology, which makes the analysis and description of flow and transport processes in such aquifers a challenging task. In this study, the solute transport behavior including fracture-matrix interaction in hydrogeological units of a limestone aquifer in eastern Denmark was characterized by designing, conducting and interpreting six depth-specific tracer tests involving natural- and forced-gradient conditions with multiple tracers representing different diffusion properties. To determine flow parameters, the tracer tests were complemented by a comprehensive set of depth-specific borehole and hydraulic tests.Based on the tests, a new and stronger conceptual understanding was developed for the different aquifer units. The investigated limestone aquifer is composed of a glacially crushed unit and two fractured units, with calcarenitic and bryozoan limestone of similar hydraulic properties. Hydraulic tests revealed, that the crushed unit has a lower hydraulic conductivity than the fractured limestone units, likely due to the crushed conditions with small limestone clusters and small-aperture fractures potentially filled with fine material.In the fractured limestone units, a distinct preferential flow and primary transport along major horizontal fractures was inferred from the tracer tests under forced-gradient conditions. The dominant horizontal fractures were identified on impeller flow logs and appear connected between wells, having an extent of up to several hundred meters. Connectivity between the aquifer units was investigated with a long-term pumping test and tracer tests, revealing restricted vertical flow and transport. A very pronounced hydraulic conductivity contrast between major fractures and matrix could also be inferred from the borehole and hydraulic tests, which is consistent with the findings from the tracer tests. However, the difference in the matrix diffusion behavior of the simultaneously injected tracers and a long tailing in the breakthrough curves revealed that matrix diffusion has a strong influence on the solute transport in the fractured limestone.