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A steady-state semianalytical solution for evaluating the hydraulic head distribution created by a rectangular underground dam that fully penetrates a sloping aquifer is proposed. The length of the dam concerns only a limited part of the aquifer width. This solution uses the second method of linearization of the nonlinear partial differential equation, a closer approximation of the exact solution, which allows for the consideration that the saturated thickness varies in space. This solution improves upon a previous solution, which was developed with the use of the first method of linearization (assuming a negligible variation in saturated thickness). Results show that the maximum differences in aquifer hydraulic head upgradient and downgradient across the centre of the dam are almost identical (deviation < 2%), even when the degree of saturation or desaturation near the dam (β) is ~50%. However, the previous solution overestimates the hydraulic head upgradient of the dam and underestimates it downgradient with deviations increasing as β increases. This study shows that if β ≤ 20% the solution with the first linearization method gives satisfactory results, which is similar to previous studies. Otherwise, it is preferable to use the new solution developed. Analysis of the solution included sensitivity tests and type curves to evaluate the maximum hydraulic differences induced by the underground dam. The proposed solution can be implemented as an operational tool for engineers designing underground dams and is meant to supplement existing hydrogeological models for improving the design of such structures. [ABSTRACT FROM AUTHOR]

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Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pumping at a large rate can convert a confined flow to a confined–unconfined one in a confined aquifer. In this paper, a new semianalytical solution is proposed to investigate the mechanism of transient confined–unconfined flow under the non-Darcian condition in a fully penetrated confined aquifer. By using Izbash's equation, a new linearization method was developed to approximate the nonlinear terms of the mathematical model of pumping-induced flow. The solution was derived by using the Laplace transform. The acceptability of the proposed solutions was verified by comparisons with numerical solutions by COMSOL Multiphysics and an analytical solution. The effects of the non-Darcian index, hydraulic conductivity, and the storativity ratio on developments of drawdown and the transient unconfined region were especially investigated. It is indicated that the non-Darcian index and the hydraulic conductivity have a positive effect on the drawdown in the confined region and a negative effect on that in the confined region, respectively. Otherwise, the drawdown simulation is negatively related to the storativity ratio. The result of this paper offers much-needed insights in the field of mine dewatering and the application of geological and hydrological conditions. [ABSTRACT FROM AUTHOR]

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We present a new methodology capable of modeling transient motion of shallow phreatic surface of groundwater in unconfined aquifers. This methodology is founded on a new and comprehensive theory for water table motion and a corresponding efficient numerical scheme. In the theoretical aspect, we derived a new set of governing equations constituted by a depth-averaged continuity equation and momentum equations based on unsteady Darcy's law. The derived governing equations are of the hyperbolic type and possess stiff terms in the momentum equations due to the inertia motion in a characteristic time scale that is relatively shorter than the time scale of seepage motion. To effectively solve the derived hyperbolic system with stiff terms, in the numerical aspect, we utilize f -wave propagation algorithm, an explicit finite volume method, that can ensure numerical convergence and well-balancing solutions when momentum is rapidly relaxing to an equilibrium of steady state. Verification is successfully performed by comparing the results with analytic solutions to the classic problem of multidimensional spreading of a groundwater mound. This study demonstrates that the proposed methodology can accurately and satisfactorily simulate the spatiotemporal distribution of shallow water table and its wetting front in unconfined aquifers. • We propose a new way to model transient shallow water table in unconfined aquifers. • We derive a hyperbolic theory using unsteady Darcy's law and a well-balanced scheme. • Analytic solution of the classic groundwater mound problem is used for verification. [ABSTRACT FROM AUTHOR]

Karst aquifers are abundant, but vulnerable water resources. Therefore, a deeper understanding of possible mechanisms that determine the properties of karst springs is crucial. In this work, we present an example of Unica Spring and Malni Spring, the two main outlets of a large karst system in the Notranjska karst region, Slovenia. Although the two springs share same catchment area, the flow distribution between them shows an interesting behaviour: At low-flow conditions Malni Spring is the main outlet, while Unica spring receives almost no water. During high water events, discharge of Malni Spring stays limited and Unica Spring becomes the main outlet. We relate these observations to the local geometry of the channels and breakdowns in the remote part of the Planinska Jama (Planina Cave), called Mysterious Lake. There, waters from Rakov Škocjan and Javorniki aquifer merge and further diverge to both springs. At low water conditions, the outflow towards the Unica Spring is restricted by the breakdown, so that most of the inflow is directed towards the Malni Spring. With increasing recharge, the level in Mysterious Lake rises until the water starts to flow over the breakdown along a system of large channels (Rak Branch of Planinska Jama) to the Unica Spring. The breakdown level keeps the hydraulic head and the flow towards Malni Spring limited. To verify this scenario, a hydraulic conduit model was made based on the known and predicted channels, and inflows calculated from the historical data of discharge measurements at related springs and ponors. An inversion procedure was used to obtain a satisfactory fit to the observed discharge data and to constrain the selected model parameters. The model accurately reproduced the observed discharge behaviour under low- and high-flow conditions. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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. [ABSTRACT FROM AUTHOR]

Groundwater sampled at the outlets of uncased flowing wells in a thick unconfined aquifer, which has undergone mixing, has been found to have hydrochemistry similar to deep groundwater in discharge areas. To identify the hydrodynamic causes, transient models of groundwater flow and age in a three-dimensional homogeneous unit basin with flowing wells are constructed to obtain flow rates in wells and groundwater mean age around wells. Inflow of groundwater to the well in the deep part leads to mixing of groundwater from different sources, and the finally mixed groundwater is found to have the same age as groundwater in the aquifer at a specific depth, termed the equivalent position (EP). EP is always found in the lower half of the flowing well, indicating that a mixed sample at the outlet could represent deep groundwater. Outflow from the well to the unconfined aquifer in the shallow part results in aging of groundwater around the well. For fully penetrating flowing wells in confined aquifers, EP is found in the upper half of the aquifer. The different relative depths of EP to the screen interval in the two types of flowing wells are mainly due to the profiles of horizontal velocity in the inflow segment, which is basically uniform in a confined aquifer but increases from zero to a maximum value in unconfined aquifers. Thus, groundwater at the outlets of topography-controlled flowing wells is a window of the deep part of a basin, and existing long-screen wells could have the potential for groundwater sampling. [ABSTRACT FROM AUTHOR]

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Understanding of the aquifer structure and its hydraulic properties provides comprehensive knowledge for proper groundwater utilisation and management. This study delineated the aquifer structure using litho-hydrostratigraphical cross-sections, and estimated the hydraulic parameters using single well pumping tests for various locations on and around Mount Meru. Results show that, the aquifer system on the flanks of Mount Meru is a sloping aquifer with sloping beds. On the far east of the eastern flank, the aquifer is composed of debris avalanche deposits, while on the north-eastern and west flanks the aquifer is composed of weathered fractured lava, whereas on the south-western flank, the aquifer is composed of different layers: pyroclastics on the top, weathered fractured lava, weathered pyroclastics, and weathered fractured lava at the bottom. The aquifer is semi-confined on the north-eastern and western flanks; on the north-eastern flank, the overlying debris avalanche deposits acting as an aquitard, while on the western flank, the overlying layers: pyroclastics and unweathered lava acting as an aquitard and aquiclude, respectively. The aquifer is unconfined on the far east of the eastern flank and south-western flank. The transmissivity of the aquifer on the north-eastern flank is substantially increasing with increasing depth, while variable, both at the shallow depth of hand-dug wells and the larger depth of boreholes, on the south-western flank; indicating aquifer heterogeneity. On the north-eastern flank, the topmost part of the aquifer, exploited by hand-dug wells, has a low transmissivity (T = 1.3 m2/d) and potential for smaller withdrawals for local water supply with limited consumption, while the upper part of the aquifer, captured by boreholes, has an intermediate transmissivity (T = 35 m2/d) and potential for local water supply, whereas the deeper part of the aquifer has a high transmissivity (T = 788 m2/d) with potential of somewhat regional importance. On the western flank, the aquifer has a very low transmissivity (T = 0.4 m2/d) and potential for local water supply with limited consumption. On the south-western flank, on average, the topmost part of the aquifer, exploited by hand-dug wells, has very low to intermediate transmissivity (range of T: 0.3–21 m2/d), leading to variable potential for smaller withdrawals for local water supply (private consumption), whereas the deeper part of the aquifer, captured by boreholes, has low to intermediate transmissivity (range of T: 9–43 m2/d) and potential for local water supply. [Display omitted] • Volcanic aquifer system. • Sloping aquifer with sloping beds. • The transmissivity of the aquifer on the north-eastern flank is substantially increasing with increasing depth. • The transmissivity of the aquifer is variable, both at the shallow depth and the larger depth on the south-western flank. • The aquifer system has variable potential. [ABSTRACT FROM AUTHOR]

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Aquifer parameters are useful for modeling sea water intrusion and other groundwater management issues in coastal areas. Oscillations in tide-induced groundwater levels contain important information of the properties of coastal aquifers and measurements of tidal effects can be employed to estimate the aquifer parameters. The solution to the transient groundwater flow model in a coastal confined aquifer with a sinusoidal fluctuation of the tide shows that the amplitude of groundwater levels is smaller than the tide, the tidal efficiency decreases exponentially with distance from the coast and the time lag increases linearly with distance from the coast. The aquifer property described by the ratio of storativity to transmissivity can be estimated if the amplitude (or tidal efficiency) and the time lag of groundwater levels are obtained based on filed measurements of tidal effects. Principle of these tidal methods is presented in this article, including those with one observation well and two observation wells. Hourly observations of the tide and groundwater levels at 14 observation wells in the coastal aquifer near Beihai, China are used to illustrate the application of these methods. The estimated ratio of storativity to transmissivity of the confined aquifer ranges from 1.66 × 10 to 4.84 × 10 d/m. For a given transmissivity of 750 m/d, the storativity of the aquifer is in the range 1.245 × 10 to 3.63 × 10. [ABSTRACT FROM AUTHOR]

A simple descriptive-statistical approach is proposed for evaluating the transmissivity of fractured-bedrock under field conditions. Based on standard well logging and identification of structural discontinuities from borehole televiewer, the approach consists of four steps: (1) determination of discontinuity properties, namely the frequency of discontinuities and the ratio of open fractures along the borehole; (2) ranking the three well logs and the discontinuity properties into tertiles (high-to-low); (3) performing statistical analysis ( F-test) for the three well logs to assess the significance of open fractures on the water-transmitting potential and then assigned a weighting factor; and (4) a semi-quantitative indicator, RGVFO, is obtained by multiplying all predictive indexes and weighting factors. It is a multi-criteria evaluation procedure that elucidates the quantitative and qualitative importance of all selected geophysical indexes. A high cross-correlation between transmissivity to RGVFO value is found, which indicates that by a combined consideration of well logging and structural discontinuities, an appropriate estimate of bedrock water-transmitting potential can be derived. [ABSTRACT FROM AUTHOR]

While in catchment and hillslope hydrology a more nuanced approach is now taken to streamflow recession analysis, in the context of major aquifers it is commonly still assumed that the groundwater head recession rate will take exponential form, an idea originally proposed in the 19th Century. However it is shown here that, in early times, the groundwater head recession in a major aquifer should take an almost straight line form with a rate approximately equal to the long-term recharge rate divided by the aquifer storage coefficient. The length of this phase can be estimated from an analytical expression derived in the paper which depends on the aquifer diffusivity, length scale, and the position of the monitoring point. A transitional phase then leads to an exponential phase after some critical time which is independent of the position of the monitoring point. Major aquifers in a state of periodic quasi-steady state are expected to have rates of groundwater flux recession which deviate little from the average rate of groundwater recharge. Where quasi-exponential groundwater declines are observed in nature, their form may be diagnostic of particular types of aquifer properties and/or boundary effects, such as proximity to drainage boundaries, variations in transmissivity with hydraulic head, storage changes due to pumping, nonequilibrium flow at a range of spatial and temporal scales, and variations in specific yield with depth. Recession analysis has applicability to a range of groundwater problems and is powerful way of gaining insight into the hydrologic functioning of an aquifer. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We have developed a drawdown solution for a partially penetrating well under constant flux pumping in a confined aquifer with finite thickness. The predictions of our solution diverge from the predictions of Hantush's solution (), particularly for problems with low ratios of well screen length to aquifer thickness. Furthermore, the predicted drawdown from Hantush's solution () differs from that of Yang et al.'s solution Water Resour Res 42:W0552, () only near the well and at small time values as indicated in Yang et al. Water Resour Res 42:W0552, (). Our solution is based on Green's function with a columnar source (sink) that represents pumping from a finite-radius well. Hantush's solution () and Yang et al.'s solution Water Resour Res 42:W0552, (), however, were derived from Laplace transform techniques for pumping in a well with an infinitesimal and a finite radius, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: Groundwaters of the Winnipeg Formation have been found to have Ba concentrations in excess of drinking groundwater guidelines over an area of several hundred square kilometers. Water samples are at or near barite saturation, however SO4 concentrations are exceedingly low. This inequality suggests that SO4 is being lost from the groundwater, allowing for a buildup of Ba in solution as barite saturation is maintained. The focus of this study is to investigate the relationship between Ba and SO4 and its application to anomalously high Ba concentrations found in the formation. These relationships are investigated through the use of transport modeling in PhreeqC. The model consists of the mixing two end-member waters that are found within the formation, reacting the mixed water with dissolved organic carbon, and transporting the newly mixed and reacted water through the formation. [Copyright &y& Elsevier]

Pumping tests are still the most reliable procedure to obtain hydrogeologic properties of the aquifer, although not always the interpretation procedures are applied properly. This can have an important impact in the magnitudes of these parameters. The new formulations and methodology for determination of hydrogeological properties in non linear flow from pumping tests already differ from those earlier proposed by Pérez Franco D. (1995, 2005) in both methods. The author stands out the importance of the second method in that it does not require two observation wells and, at the same time, it is possible to obtain the equation to find out structural losses or pumping well imperfections, which are of great importance in the knowledge of its efficiency. [ABSTRACT FROM AUTHOR]

Summary: To better understand the spatial distribution of groundwater salinisation in western Victoria, southeast Australia, the interactions between a surficial basalt aquifer and an underlying extensive palaeodrainage (‘deep lead’) system were studied using a multi-disciplinary approach, combining strontium isotope analyses with major ion chemistry and the interpretation of geological and hydrogeological data. The strontium isotopes proved particularly useful in delineating flow paths and hydraulic connections between the two aquifers, which have contrasting 87Sr/86Sr ratios. The freshest basalt groundwaters lie beneath volcanoes and have 87Sr/86Sr signatures close to the whole-rock strontium isotope ratios of the basalts (∼0.7045), indicating the strong influence of basalt weathering. With increasing distance from the eruption points, basalt groundwaters become progressively more saline and the strontium isotope ratios evolve towards the more radiogenic signatures of local rainfall (0.710–0.711), due to the slow addition of infiltration concentrated by evapotranspiration during its passage through the thick, clay-rich soils developed on the basalt lavas. Overall, the influence of rainwater on the strontium isotope signatures of the basalt groundwater is much greater than that of basaltic weathering, indicating that rainwater can play a greater role in determining groundwater strontium composition than is often realised. Most parts of the palaeodrainage system beneath the basalt are preferentially recharged through the volcanoes, as shown by strong downwards hydraulic gradients and groundwater 87Sr/86Sr ratios similar to the least radiogenic basalt groundwaters. However, in the northwestern part, groundwater 87Sr/86Sr ratios are closer to those of the source material of the sediments (Palaeozoic bedrock), indicating that here recharge occurs predominantly in the headwaters where the basalts are absent. In the southern and western sections of the palaeodrainage system there is an upward flux into the overlying basalts, as shown by strong upward hydraulic gradients and elevated strontium isotope signatures in basalt groundwaters. This occurs because lateral groundwater flow in the palaeodrainage system is restricted by shallow subsurface basement ridges, and ultimately discharges to the surface as salt lakes. [Copyright &y& Elsevier]

Summary: Wave setup is the elevated mean water-table at the coast associated with the momentum transfer of wave breaking, which occurs generally over several days. Groundwater responses to wave setup were observed as far as 5km inland in central Maui, Hawaii. The analysis showed that at times of energetic swell events wave-driven water-table overheights dominate low-frequency groundwater fluctuations associated with barometric pressure effects. Matching peak frequencies at 1.7×10−6 Hz and 3.7×10−6 Hz were identified in setup and observed head using spectral decomposition. Similar to tides, the setup propagation through the aquifer shows exponentially decreasing amplitudes and linearly increasing time lags. Due to the longer periods of setup oscillations, the signal propagates deeper into the aquifer (∼10km in central Maui) than diurnal tides (5km) and can therefore provide information on greater length scales. Hydraulic diffusivity was estimated based on the setup propagation. An effective diffusivity of 2.3×107 m2/d is consistent with aquifer parameters based on aquifer tests and tides. A one-dimensional numerical model supports the results of the analytical solution and strengthens the suitability to estimate hydraulic parameters from setup propagation. The methodology is expected to be beneficial to high-permeability coastal environments, such as on volcanic islands and atolls. [Copyright &y& Elsevier]

Highlights: [•] We include anisotropy in the new development of the second-order theory. [•] The bank-storage problem is used as test case. [•] A new analytical solution to the second-order theory is presented. [ABSTRACT FROM AUTHOR]

Within the arid Tata River catchment of the Moroccan Anti-Atlas Mountains groundwater is the only source for drinking and irrigation water supply. Nevertheless, the hydrogeological and hydrogeochemical setting of the area is understudied. In order to develop sustainable groundwater management strategies a profound understanding of the region's groundwater system is essential. In terms of comprehensive field surveys, aquifer structure and properties as well as water composition were evaluated. The Lower Cambrian Limestone and Dolomite Series as well as the Quaternary sediments were identified to be the major aquifer systems. Isotopic signatures of groundwater indicate direct groundwater recharge trough fractures and a major flow direction similar to the drainage system of the Tata River. Hydrochemical composition mainly reflects the mineralogy. The primary processes are calcite and bassanite dissolution as well as dedolomitization and feldspar weathering. Water of irrigation return flow drains downstream and is pumped repeatedly, with each cycle contributing to contamination and water loss through evaporation, while the water is used for irrigation and daily needs. In turn, groundwater quality decreases along its flow path from N to S. The hydrogeological conceptual model, visualizing all results, can be used by stakeholders to integrate groundwater related aspects into site-specific agricultural practices as well as to set up numerical flow and transport models. Image 1 • Direct groundwater recharge occurs at elevated areas. • Statistics and ion ratios show feldspar, calcite, and bassanite weathering. • Hydrochemistry and isotopes indicate irrigation water return flow. • Groundwater quality decreases along its flow path from N to S due to human activities. • Hydrogeological conceptual model is a base for a sustainable groundwater management. [ABSTRACT FROM AUTHOR]