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In the nature, most phreatic or confined aquifers are of layered distribution. Based on the actual distribution of aquifer and whether there exists transfluence contact between each aquifer, the layered distribution aquifer basically is simplified as multi-aquifer or double aquifer structure. In this paper, all of the aquifer structure models proposed by domestic and foreign scholars are summarized. Furthermore, the mathematical model of each aquifer structure is detailed illustrated.

SUMMARY Artesian mound springs occur along the south-western edge of the Great Artesian Basin, in northern South Australia, but their underground structure and relationship to faulting is not well understood. We have performed geophysical surveys over three different systems using a range of techniques: early-time TEM, self-potential, and magnetotellurics. The self-potential data contains a local response due to specific spring vents, and also a broader stronger response due to laterally extensive upwelling in the lower part of the Bulldog Shale, at depths of approximately 100 m. Modelling of TEM and magnetotelluric data show that the confining Bulldog Shale, which is generally very conductive, contains resistive areas underneath springs and spring complexes which are believed to be related to spring-related carbonate deposition. Magnetotelluric modelling in particular indicates that anisotropic resistivity in the form of vertical sheets at a depth of 100 to 200 m, can explain the observations more readily than a conductive 2D feature, suggesting that the structures underlying the springs are sets of closely-spaced faults. The orientation of this anisotropy matches the regional NNW/SSE orientation of spring complexes.

The physicochemical parameters of the sulphide spring water from a 500 m deep artesian borehole in Sovra Valley (Slovenia) are stable, with very little variation: temperature, 9.2 ± 0.0 °C; pH 7.70 ± 0.11; specific electrical conductivity, 777 ± 8 μS/cm; and dissolved oxygen, 0.19 ± 0.11 mg/l. The water from the borehole is hard, rich in sulphates, and has a notable concentration of sulphide, while it is low in chlorides. Communities of phototrophs were analysed at the oxygenic ecocline at the outflow from the borehole, and from further downstream. Caloneis tenuis, Frustulla vulgaris, Gomphonema sp., Navicula radiosa, Oscillatoria sp., and Tribonema vulgare successfully thrive exclusively at the outflow from the borehole under sub-optimum conditions for the majority of phototrophs. Downstream from the borehole, where the hydrogen sulphide degasses, autotrophic biofilms were dominated by different diatoms. The Bray–Curtis similarity index confirms the distinctive phototrophic communities along the oxygenic ecocline downstream from the sulphidic spring. The sulphidic ecocline downstream from the spring is indicative of the composition of phototrophic communities, as some species appear only downstream from the spring. An ecocline downstream from the borehole of the sulphidic spring was reflected also in the bacterial indicator groups. This study brings novel insights to the limited knowledge in the field of oxygenic phototrophy related to sulphidic springs.

Summary The recent Canterbury/Christchurch earthquakes and aftershocks generated groundwater level responses throughout New Zealand. However, the greater part of damage has been sustained by the city of Christchurch which is built on a layered sequence of artesian aquifers. In this paper we focus on responses in these coastal aquifers. We quantify groundwater responses with a simple model which differentiates between immediate earthquake induced response (spike) and post-seismic change (offset). The most significant feature of our analysis is the consistent pattern of groundwater response to the earthquakes: deeper wells correlate with negative offset and shallower wells correlate with positive offset. This is consistent with the upwards vertical movement of water. We consider the hydrological and engineering consequences.

This study investigates the feasibility of management of aquifer recharge (MAR) in Lebanon by designing well barriers to remove seawater intrusion from the fractured carbonate aquifers. Groundwater flow and saltwater/freshwater 50% sharp interface have been modeled along the coastal area using the Ghyben eHerzberg theory. The groundwater flow simulations have been supported by field transmissivity estimations and depth measurements carried out on 44 wells during 2003. Results have shown the seawater intrusion in coastal aquifers at Jieh and Damour regions. Three well-injection barriers have been proposed. The water volumes for recharge and the barrier positions have been defined by means of groundwater flow simulations. MAR can provide a valuable contribution to colloid (even pathogen) removal from injectant water, although during water infiltration in subsoil the reduction of aquifer permeability causes clogging. A simple new model for estimating the soil-rock permeability reduction due to the well clogging has been presented. The MAR, including the soil aquifer treatment at Damour and Jieh regions, has been studied by considering aquifer transmissivity (and soil porosity) reduction caused by clogging. Furthermore, the appropriate mixing of the injectant water by using reclaimed water, groundwater and surface water can be simulated using the proposed models. The time required to achieve 5% of rock permeability reduction at the proposed well barriers ranged from 71 to 935 d, by changing water quality and flow rate for recharge. This study can assist regional governments with water management in areas affected by scarcity of freshwater by implementing appropriate well-barrier projects.

A large amount of field and experimental data has been devoted to rectangular excavations thus far. In contrast, very few data were available for cylindrical excavations, especially those with large diameters in thick soft clay deposits. Via a comprehensive instrumentation program on a 100-m-wide×25.89-m-deep unpropped (self-supported) cylindrical excavation constructed by the bottom-up method in Shanghai soft clay, the characteristics of this large-sized circular excavation were extensively investigated. This cylindrical shaft was a part of a large-scale deep foundation pit excavated by the central-island technique. The investigated items included (1) lateral wall deflections, (2) vertical wall movements, (3) lateral ground movements, (4) ground settlements, (5) subsurface settlements, (6) basal heaves, (7) vertical column movements, (8) column stresses, and (9) variation of pore pressures along depth and artesian water levels. Analysis of the field data indicates that discharging of the deep art...

Because of its large size (30,000 m2 in plan), the 17.85- to 25.89-m-deep foundation pit of the 492-m-high Shanghai World Finance Center building was excavated by the central-island technique, i.e., bottom-up construction of the central cylindrical shaft first and then top-down construction of the peripheral rectangular pit. As part of the comprehensive study on the characteristics of this large-scale foundation pit, this study mainly focuses on the behaviors of the peripheral pit via the following investigated items: (1) lateral wall deflections; (2) vertical wall movements; (3) lateral ground movements; (4) axial forces in the cast floor slabs and braced struts; (5) lateral earth pressures on both sides of retaining walls; (6) variation of pore pressures along depth and deep artesian water levels; (7) ground settlements; (8) subsurface settlements; (9) basal heaves; (10) vertical column movements; and (11) column stresses. To explore the potential effects of pit sizes on the excavation behaviors...

In late 1907, Charles Fraser, the Victorian government entomologist, travelled to North Queensland. His observations of the flora and fauna in this part of Australia were later published in theVictorian Naturalist. However, this journey was not motivated entirely by his desire to study natural history. As a sufferer of ‘rhematic [sic] troubles’, he spent a few days soaking in the mineral-impregnated waters at Innot Hot Springs, a small inland village approximately 150 kilometres south-east of Cairns. First established in the late 1880s, the tiny settlement is still visited during the winter months by many ‘grey nomads’ en route to Karumba, where the fishing is promoted as being excellent. They break their journey at Innot Hot Springs to soak in the indoor or outdoor swimming pools filled with mineralised water of varying temperatures sourced from the nearby Nettle Creek. Some view it simply as a place to relax after the long journey from southern Australia, having perhaps already tried the artesian bore water baths at Moree and Mitchell en route. Others may consider the mineral waters to have healing qualities; like Charles Fraser, they are literally ‘taking the waters’.

Few studies have investigated large reaches of rivers in which multiple sources of groundwater are responsible for maintaining baseflow. This paper builds upon previous work undertaken along the Fitzroy River, one of the largest perennial river systems in north-western Australia. Synoptic regional-scale sampling of both river water and groundwater for a suite of environmental tracers ((4) He, (87) Sr/(86) Sr, (222) Rn and major ions), and subsequent modeling of tracer behavior in the river, has enabled definition and quantification of groundwater input from at least three different sources. We show unambiguous evidence of both shallow "local" groundwater, possibly recharged to alluvial aquifers beneath the adjacent floodplain during recent high-flow events, and old "regional" groundwater introduced via artesian flow from deep confined aquifers. We also invoke hyporheic exchange and either bank return flow or parafluvial flow to account for background (222) Rn activities and anomalous chloride trends along river reaches where there is no evidence of the local or regional groundwater inputs. Vertical conductivity sections acquired through an airborne electromagnetic (AEM) survey provide insights to the architecture of the aquifers associated with these sources and general groundwater quality characteristics. These data indicate fresh groundwater from about 300 m below ground preferentially discharging to the river, at locations consistent with those inferred from tracer data. The results demonstrate how sampling rivers for multiple environmental tracers of different types-including stable and radioactive isotopes, dissolved gases and major ions-can significantly improve conceptualization of groundwater-surface water interaction processes, particularly when coupled with geophysical techniques in complex hydrogeological settings.

Geochemical analyses of groundwater samples from the Djeffara confined aquifer (Southern Tunisia) were performed. The distribution of saline waters was investigated to identify the origin of the groundwater contamination. The aquifer was shown to be affected by an abnormal increase in groundwater salinity. Near the recharge zone, the groundwater salinity does not exceed 2.5 g l −1 but reaches 7 g l −1 in the northeast of the study area. Due to over pumping, groundwater level decline is so important that it disturbs the equilibrium between fresh and saline waters. The salinity distribution coupled with the structure and geology of the Djeffara aquifer suggest current seawater intrusion is possible through the deep fault systems affecting the zone. The groundwater level was shown to be highly correlated with the sea level fluctuation in the area near the fault systems, suggesting a communication between the sea and the confined aquifer. Groundwater salinization is probably related to infiltration of seawater through the faults. However, an intrusion on the side of the discharge area of the aquifer may also be possible. The bromide and chlorine analyses coupled with the SO 4 /Cl ratio confirmed that the mixing between fresh and saline waters is the main origin of groundwater salinization.

The study aims to identify and describe the dominant hydrogeochemical processes and their contribution to the overall groundwater quality of an aquifer situated in the vicinity of a mine process water dam. The study site is located in a typical Karoo Basin of Southern Africa. Groundwater samples were collected from a network of boreholes designed to monitor the migration of contamination from the mine process water dam during a five year period from November 2007 to November 2011. The study utilises the expanded Durov diagram, bivariate plots and correlation coefficients statistics to analyse groundwater chemistry data. Based on analyses of the groundwater chemistry the study area was divided into two hydrogeochemical zones; the fresh background and contaminated groundwater. Fresh water in the background aquifer is characterised by a Na+– HCO 3 - hydrochemical groundwater type. Groundwater in the contaminated zone comprises of Mg2+–Cl− and Na+–Cl−, two main hydrochemical water types. High levels of EC and TDS that ranges from 63.10 to 1870 mS/m and 690–11443 mg/l respectively were measured in the contaminated groundwater indicating that the aquifer has been affected by saline water from the dam. Major ions of Mg2+, SO 4 2 - and Ca2+ measured in the contaminated portion of the aquifer are positively correlated to the conservative Cl− indicating that these ions were derived from the same saline source (dam). The study identified albite dissolution as the main hydrogeochemical process responsible for the evolution of fresh groundwater chemistry in the background aquifer. The aquifer on the down gradient of the process water dam is contaminated by saline water that evolved from the dam. There is evidence to show that the mine process water dam poses a serious threat of contaminating the groundwater with salts. A recommendation was therefore made to the responsible authorities to consider decommissioning of the facility given that the mine operations ceased some years back.

When the buried depth of water level is very large, the air compressor is used in pumping test. In the limited conditions, the value of the water level was not measured, but the recovery value of water level could be measured. In this case, the sp value of the water level drawdown was not able to be measured accurately when the pumping test stopped. So the hydraulic conductivity of aquifer could only be determined according to the linear graphic method of the water level recovery test. However, water level recovery characteristics of each period were not the same, and the raising rate of water level were not equal. Thus, there was a deviation when the hydraulic conductivity was solved with the linear graphic method. According to the existing data, the thesis combined the water level recovery fitting of the entire curve fitting with Dupuit formula of artesian well, determining the sp value and hydrogeological parameters of aquifer. After comprehensive analysis, the parameters obtained are more reasonable, which can provide a good reference for in-situ mining of oil shale in this area.

The Quaternary deposits in Shanghai primarily consists of a phreatic aquifer group (Aq0) and five artesian aquifers (AqI–AqV) that are separated by six aquitards (AdI–AdVI). In the basin of the Huangpu River, the first artesian aquifer (AqI) is connected to the second artesian aquifer (AqII), forming a 50-m-thick artesian aquifer with a very high groundwater level. The highway tunnels under the Huangpu River of Shanghai are constructed at a maximum depth up to 45 m, within the artesian aquifer. These tunnels are lined with precast reinforced concrete segments without a second lining. Under high water pressure, it is difficult for the single shell linings to achieve water tightness. Different degrees of groundwater leakage have been observed in road tunnels under the Huangpu River. The tunnels constructed before the 1990s have had very serious groundwater leakage (e.g., >1 L/m2/day), and the recently constructed tunnels have leaked less than 0.1 L/m2/day. The factors influencing groundwater leakage include depth below groundwater level, differential settlement of the tunnel, and applied waterproof technologies. The increase in depth leads to a significant increase in groundwater leakage. The differential settlement causes gaps to open and offset between segments, as well as cracking of segments, which can also induce groundwater leakage. According to the analysis of recorded data, the number of leaking points tends to increase with the curvature of the settlement curve. In addition, inappropriate waterproofing materials and poor waterproofing design will also lead to groundwater leakage. Groundwater leakage causes deterioration of the structure, aging of the installations in the tunnels (e.g., facilities and pavements), as well as discomfort for users of the tunnels and adverse environmental impacts. Furthermore, groundwater leakage also causes structural deformation of the tunnel itself, leading to further leakage and hazards.

Korba aquifer is one of the most typical examples of overexploited coastal aquifer in the Mediterranean countries. In fact, from 1985, a considerable piezometric level drop, water salinization, and seawater intrusion were registered in the aquifer. In December 2008, Tunisian authorities initiated a general plan to groundwater management in order to augment groundwater resources, restore the piezometric levels, and improve water quality. The plan consists of artificial recharge of groundwater used treated wastewater through three infiltration basins. During the first 4 years (from December 2008 to December 2012), 1.41 Mm3 of treated wastewater was injected to the Korba aquifer. This study presents a hydrogeological assessment of groundwater evolution during the recharge processes. In this study, 32 piezometric and chemical surveys of 70 piezometers and observed wells are used to present hydrogeological investigation and water quality evolution of wastewater reuse through artificial recharge in Korba coastal aquifer. The piezometric evolution maps are used to specify the positive effect in groundwater level that exceeding 1.5 m in some regions. The interpretation of salinity evolution maps are used to indicate the improving of groundwater quality.

The Gavbast karstic aquifer located in southern Iran is in direct contact with an exposed salt diapir. To assess the influence of the diapir on the quality of groundwater in the karstic aquifer, electrical conductivity, total dissolved solids, flow rate, temperature and major ion concentrations were measured at 57 sampling sites, including springs, surface waters and wells. A conceptual model of groundwater flow is proposed for the Gavbast karstic aquifer based on the geological setting, water budget, local base of erosion, and hydrochemistry of the sampling sites. The model suggests two subbasins in the Gavbast Anticline draining into two distinct discharging alluvial sections. Unexpectedly, groundwater discharging from the carbonate Gavbast aquifer is saline or brackish and water is of chloride type. The study indicates that the source of salinity of the Gavbast aquifers is infiltration of surface diapir-derived brine into the aquifer. The contribution of the diapir brine in the Gavbast karst aquifer is calculated about 4 L/s, using chloride mass balance. Construction of salt basins to evaporate brine discharging from the diapir springs is proposed to reduce the salinity of karst water. A row of strategically placed wells in the Gavbast karst aquifer would potentially exploit large volumes of fresh groundwater before it is contaminated by the salt. Such low-cost remediation should allow the agricultural exploitation of 40 km2 of currently barren land.

The current study introduces the geological subsurface cross-sections in the southern part of the Gaza Strip to show the structure of the aquifer in the area. The cross-sections give evidence of four subaquifers of the coastal aquifer in the southern part of the Gaza Strip. These cross-sections give the natural reasons for the deterioration of the groundwater in the study area. The results show presence of clay lenses that prevent the replenishment processes of the aquifer of fresh water from the rainfall and returns flow from agricultural activities. Lithological formation was evident as one of the natural causes which accelerate destroying process of the coastal aquifer. The results also show that the structure of the aquifer causes the increase of the groundwater salinity in the Gaza Strip. The cross-sections had shown the shortage of storage capacity of high quantities of fresh water in the coastal aquifer in these areas. The role of lithological formation was evident as one of the natural causes to accelerate the process of destroying the coastal aquifer.

Indicators of quality and safety, as well as the useful properties of spring water, artesian bottled water and water from a municipal water supply systems are assessed. All the investigated samples of bottled drinking well water satisfy regulatory requirements for defined quality parameters. Biotesting analysis of the samples of water using two test organisms: crustacean Daphnia Magna and freshwater aquarium fish Poecillia Reticulata Peters confirmed the presence of different pollutants in spring water. Risks of oral use of investigated water are calculated. In terms of the quality of groundwater for the study area is characterized by Russian acceptable level of risk, which indicates a moderate anthropogenic pressure on ecosystems and the environment.

[1] Water level rises associated with river flow events induce both pressure and solute movement into adjacent aquifers at vastly different rates. We present a simple analytical solution that relates the travel time and travel distance of solutes into an aquifer following river stage rise to aquifer properties. Combination with an existing solution for pressure propagation indicates that the ratio of solute to pressure travel times is proportional to the ratio of the volume of water stored in the aquifer before the river stage rise and the volume added by the stage rise and is independent of hydraulic conductivity. Two-dimensional numerical simulations of an aquifer slice perpendicular to a river demonstrate that the solutions are broadly applicable to variably saturated aquifers and partially penetrating rivers. The solutions remain applicable where river stage rise and fall occur, provided that regional hydraulic gradients are low and the duration of the river stage rise is less than pressure and solute travel times to the observation point in the aquifer. Consequently, the solutions provide new insight into the relationships between aquifer properties and distance and time of solute propagation and, in some cases, may be used to estimate system characteristics. Travel time metrics obtained for a flood event in the Cockburn River in eastern Australia using electrical conductivity measurements enabled estimates of aquifer properties and a lateral extent of river-aquifer mixing of 25 m. A detailed time series of any soluble tracer with distinctly different concentrations in river water and groundwater may be used.

The southwestern part of Egypt (East El Oweinat) is an arid area with no surface water and only one resource of useable groundwater in the well-known Nubian Sandstone aquifer. This resource has been heavily exploited since 1990, which has led to a continuous decline in the potentiometric surface of this aquifer. The groundwater recharge in the concerned area depends exclusively on the subsurface inflow across the Egyptian/Sudanese borders. A FEFLOW, finite element groundwater model, has been used to investigate the length of the recharge window and to predict the hydrodynamic impacts of different groundwater extractions on the potentiometry of this aquifer. A complete database of the hydrogeological and drilling information of about 600 water wells drilled in the period 1985–2010 was evaluated and used for the model parameter input as well as for its simulation. The results of steady-state simulation indicate that the length of the southwest flux boundary is about 170 km with angle flow direction about 52°NW with a groundwater flow rate about 0.018 m/day. A calibrated regional numerical model with refined grid on the pumping centres, hydraulic properties and flux boundary in the southwest is used to simulate the impacts of the present and planned groundwater extraction on the potentiometry of the aquifer. The results show a real danger of increasing the water depth to uneconomic lifting depth. Through implementation of 135 pumping wells in time 2002–2008, the lowering of water table ranges from 1 to 1.5 m in the reclamation areas. On the other hand, the distribution of 1600 proposed wells with distance between every two adjacent wells not less than 2700 m indicates that the lowering of water table ranges from 5 m away of the reclamation areas to 15 m in the reclamation areas in time period of 27 years (2008–2035). This result seems to be the better for the present irrigation project in East El Oweinat area.

This study delineates the actual hydrogeochemistry and the geological evolution of an unconfined coastal aquifer located in a lowland setting in order to understand the drivers of the groundwater salinization. Physical aquifer parameterization highlights a vertical hydraulic gradient due to the presence of a heavy drainage system, which controls the hydrodynamics of this coastal area, forcing groundwater to flow from the bottom toward the top of the aquifer. As a consequence, relict seawater in stable density stratification, preserved within low permeability sediments in the deepest portion of the aquifer, has been drawn upward. The hydrogeochemical investigations allow identifying the role of seepage and water-sediment interactions in the aquifer salinization process and in the modification of groundwater chemistry. Mixing between freshwater and saltwater occurs; however, it is neither the only nor the dominant process driving groundwater hydrochemistry. In the aquifer several concurring and competing water-sediment interactions - as NaCl solution, ion-exchange, calcite and dolomite dissolution/precipitation, oxidation of organic matter, and sulfate bacterial reduction - are triggered by or overlap freshwater-saltwater mixing The hyper-salinity found in the deepest portion of the aquifer cannot be associated with present seawater intrusion, but suggests the presence of salt water of marine origin, which was trapped in the inter-basin during the Holocene transgression. The results of this study contribute to a better understanding of groundwater dynamics and salinization processes in this lowland coastal aquifer. © 2013 Elsevier B.V.

article i nfo Aquitards are capable of generating and preserving large amounts of chemicals. The release of the chemicals from the aquitards poses a potential contamination risk to groundwater that may be used as a drinking water source. This work aimed to identify the contribution of hydrogeochemical processes in the aquitards to groundwater hydrochemistry in the underlying confined basal aquifer by studying the coastal Quaternary aquifer-aquitard system of the Pearl River Delta, China. The system was submerged by paleo-seawater in the early Holocene and mainly receives infiltration of precipitation at present, as indicated by investigations on stable isotopes (δ 2 H, δ 18 O), water chemistry (SO4 2� and Cl � ) and salinity. Significant correlations between total dissolved solids in the basal aquifer and the thickness of the overlying aquitard further suggested the contribution of the aquitard to the groundwater hydrochemistry in the aquifer. Significant correlations between the chloride concentrations in aquitard porewater and that in groundwater in the aquifer, and between the thickness of the aquitard and the chloride concentrations in groundwater indicated the strong influence of the aquitard on the chloride in the aquifer. This is probably because the low-permeability aquitard is capable of preserving the paleo-seawater in the aquifer and releasing the salinity from the aquitard down to the aquifer via downward flow or diffusion. Isotopic and geochemical studies revealed that the aquitard is also responsible for generating and preserving large amounts of naturally occurring ammonium. Analysis between the concentrations of ammonium in groundwater in the basal aquifer and the total available ammonium in aquitard sediments suggested that the former is significantly controlled by the latter.

The Guarani aquifer system (GAS) represents one of the biggest aquifers in the world and is the most relevant groundwater resource in South America. For the first time, by combining field and laboratory measurements, a high-resolution aquifer analog model of fluvial–aeolian sediments of the GAS in Sao Paulo State (Brazil) is constructed. Three parallel sections of frontal outcrops, 28 m × 5.8 m, and two parallel sections of lateral outcrops, 7 m × 5.8 m, are recorded during open-pit mining of sandy sediments and describe in detail the three-dimensional distribution of the local lithofacies and hydrofacies. Variations of hydraulic conductivity, K, and porosity, n, are resolved on the centimeter scale, and the most permeable units of the fluvial–aeolian facies association are identified. The constructed aquifer analog model shows moderate hydraulic heterogeneity and a mean K value of 1.36 × 10−4 m/s, which is greater than the reported range of K values for the entire GAS in Sao Paulo State. The results suggest that the examined sedimentary unit constitutes a relevant portion of the GAS in Sao Paulo State in the context of groundwater extraction and pollution. Moreover, the constructed aquifer analog is considered an ideal basis for future numerical model experiments, aiming at in-depth understanding of the groundwater flow and contaminant transport patterns at this GAS portion or at comparable fluvial–aeolian facies associations.

The effectiveness of carbon capture and geologic storage depends on many factors, including and especially the permeability of the reservoir’s caprock. While caprock integrity is generally assumed if petroleum has been preserved, it is poorly constrained in reservoirs containing only saline waters, and CO2 leakage poses a potential risk to shallow aquifers. Naturally-occurring He accumulates in pore waters over time with the concentration being strongly dependent on the long term flux of fluid through the caprock. Furthermore, a small fraction of pore-water He diffuses into quartz and this may be used as a proxy for He concentrations in pore water, where dissolved gas samples are difficult to obtain, such as in deep sedimentary basins. In this paper He contained in quartz grains is measured and compared to previously measured pore water concentrations. Quartz was purified from core samples from the San Juan Basin, New Mexico and the Great Artesian Basin, South Australia. Quartz separates were heated at 290 °C to release He from the quartz. The quartz from the San Juan Basin and high purity quartz from the Spruce Pine Intrusion, North Carolina was repeatedly impregnated at varying pressures using pure He, heated and analyzed to build He sorption isotherms. The isotherms appear linear but vary between samples, possibly due to fluid inclusions within the quartz grains as high purity quartz samples partition only 1.5% of He that partitions into San Juan Basin samples. Concentrations of He in the pore water were calculated using the He-accessible volume of the quartz and the air–water He solubility. The mean San Juan Basin He pore water concentration was 2 × 10–5 cc STP He/g water, ∼400 times greater than atmospheric solubility. Great Artesian Basin samples contain a mean He concentration of 3 × 10–6 cc STP He/g water or 65 times greater than atmospheric solubility. However, pore water He concentrations in both the San Juan and Great Artesian Basins differ by up to an order of magnitude compared to samples collected with an alternate method. The reason for the offset is attributable to either partial saturation of the pore volume or a lack of He equilibrium between quartz and pore water. Coating of clay or other mineral phases on quartz grains, which tends to reduce the effective diffusion coefficient, may cause the latter. This technique of assessing permeability is promising due to the abundance of existing core samples from numerous basins where carbon sequestration may ultimately occur.

[1] Hydrologic models of the oceanic crust commonly assume that the uppermost igneous extrusive layer of the aquifer is thermally well mixed, although this assumption has not been rigorously tested. Here, the assumption of a thermally well-mixed aquifer is tested against the geological record using O isotope-derived crystallization temperatures of carbonates in the lavas as a record of the temperatures experienced by the aquifer. It is found that carbonate formation temperatures are higher than can be explained by a model of outcrop-to-outcrop flow in a well-mixed aquifer at four of the seven drilling locations analyzed. A poorly mixed aquifer is developed to further explore the crustal hydrology at these locations. Relative to a well-mixed aquifer, a poorly mixed aquifer can achieve higher average temperatures, develops larger lateral pressure gradients driving flow, and requires a lower permeability to achieve a given lateral fluid flux. O isotope data from most of the carbonate samples analyzed are consistent with temperatures achievable in a poorly mixed aquifer; those samples which are not consistent can be explained by plausible special circumstances (such as formation at a discharge zone, where ascending fluid may warm the uppermost aquifer).

Analytical solutions for the water table and lateral discharge in a heterogeneous unconfined aquifer with time-dependent source and fluctuating river stage were derived and compared with those in an equivalent homogeneous aquifer. The heterogeneous aquifer considered consists of a number of sections of different hydraulic conductivity values. The source term and river stage were assumed to be time-dependent but spatially uniform. The solutions derived is useful in studying various groundwater flow problems in a horizontally heterogeneous aquifer since the spatially piecewise-constant hydraulic conductivity and temporally piecewise-constant recharge and lateral discharge can be used to quantify variations in these processes commonly observed in reality. Applying the solutions derived to an aquifer of three sections of different hydraulic conductivity values shown that (1) the aquifer heterogeneity significantly increases the spatial variation of the water table and thus its gradient but it has little effect on lateral discharge in the case of temporally and spatially uniform recharge, (2) the time-dependent but spatially uniform recharge increases the temporal variation of groundwater table over the entire aquifer but its effect on lateral discharge is limited in the zone near the river, and (3) the effect of river stage fluctuation on the water table and lateral discharge is limited in the zone near the river and the effect of the heterogeneity is to increase lateral discharge to or recharge from the river.

During the last few decades, the Grombalia shallow, an unconfined aquifer, had been under stress by groundwater pumping due to the increasing population and development of agricultural activity. Recently, the aquifer has displayed an important decline in the water level of boreholes and wells, and considerable deterioration of groundwater quality due to saltwater intrusion. A groundwater numerical model for the Grombalia aquifer has been developed based on the Visual Modflow 3.1 code to simulate the groundwater changes under steady state regime and transient conditions. The results of the model show reasonable agreement between observed and estimated groundwater levels in the observation wells. Sebkaht Soliman wetland aquifer connection has been identified. This paper presents the effect of different groundwater management scenarios and pumping discharge on groundwater resources in the Grombalia aquifer (Cap-Bon peninsula, Tunisia).

Aquifer-based groundwater quality assessment offers critical insight into the major hydrochemical processes, and aids in making groundwater resources management decisions. The Texas Rolling Plains (TRP), spanning over 22 counties, is a major agro-ecological region in Texas from where highest groundwater nitrate (NO3 −) levels in the state have been reported. In this study, we present a comparative assessment of major hydrochemical facies pertaining to NO3 − contamination and a host of species such as sulfate (SO4 2−), chloride (Cl−), and total dissolved solids (TDS) in different water use classes in the Seymour and Blaine aquifers, underlying the TRP. Aquifer-stratified groundwater quality information from 1990 to 2010 was obtained from the Texas Water Development Board and aggregated over decadal scale. High groundwater salinization was found in the municipal water use class in the Blaine aquifer with about 100, 87 and 50 % of observations exceeding the secondary maximum contaminant level for TDS, SO4 2−, and Cl−, respectively in the 2000s (2000–2010). The NO3-contamination was more alarming in the Seymour aquifer with 82 and 61 % of observations, respectively, exceeding the maximum contaminant level (MCL) in the irrigation and municipal water use classes in the 2000s. Salinization was more influenced by SO4 2− and Cl− in the Blaine aquifer and by NO3 − in the Seymour aquifer. High NO3 − (>MCL) observations in the Seymour aquifer occurred in the Ca–HCO3 and Ca–Mg–HCO3 facies, the domains of fresh water recharge and anthropogenic influences (e.g., agricultural activities, waste disposal). High SO4 2−, Cl− and TDS observations in the Blaine aquifer dominated the Ca–Cl, Na–Cl, and mixed Ca(Mg)–SO4(Cl) facies indicating evaporite dissolution, mixing and solute exchange, and lack of fresh recharge.

Subsurface flow and heat transport near Freienbrink, NE Germany, was simulated in order to study groundwater–surface water exchange between a floodplains aquifer and a section of the lowland River Spree and an adjacent oxbow. Groundwater exfiltration was the dominant process, and only fast surface water level rises resulted in temporary infiltration into the aquifer. The main groundwater flow paths are identified based on a 3D groundwater flow model. To estimate mass fluxes across the aquifer–surface water interfaces, a 2D flow and heat transport modelling approach along a transect of 12 piezometers was performed. Results of steady-state and transient water level simulations show an overall high accuracy with a Spearman coefficient ρ = 0.9996 and root mean square error (RMSE) = 0.008 m. Based on small groundwater flow velocities of about 10−7 to 10−6 ms−1, mean groundwater exfiltration rates of 233 l m−2 d−1 are calculated. Short periods of surface water infiltration into the aquifer do not exceed 10 days, and the infiltration rates are in the same range. The heat transport was modelled with slightly less accuracy (ρ = 0.8359 and RMSE = 0.34 °C). In contrast to the predominant groundwater exfiltration, surface water temperatures determine the calculated temperatures in the upper aquifer below both surface water bodies down to 10 m during the whole simulation period. These findings emphasize prevailing of heat conduction over advection in the upper aquifer zones, which seems to be typical for lowland streams with sandy aquifer materials and low hydraulic gradients. Moreover, this study shows the potential of coupled numerical flow and heat transport modelling to understand groundwater–surface water exchange processes in detail. Copyright © 2013 John Wiley & Sons, Ltd.

Leakage of water into the semi-confined Memphis aquifer near the Sheahan well field in Memphis, Tennessee, has been suggested by many studies extending back to the 1960s. A leakage pathway from Nonconnah Creek to the Sheahan well field was investigated over a 1-year period using multiple approaches: (1) stream discharge data, (2) hydraulic head data, (3) geochemical and environmental tracer (3H/3He and chlorofluorocarbon) studies, and (4) geochemical modeling. The stream loss data strongly support the conclusion that losses from the creek contribute at least 2,600 m3/d to the shallow aquifer, and hydraulic head data consistently indicate the majority of this infiltrated surface water flows within the shallow aquifer toward the Sheahan well field. Tritium-3He data from shallow aquifer monitoring wells within the Sheahan well field are composed of modern water with ages that generally increase with distance from the creek toward the well field. The leakage pathway from the creek to the well field is interpreted to involve seepage of creek waters into the shallow aquifer, mixing with other water sources and chemical reactions as the infiltrated waters flow in the shallow aquifer along a paleovalley toward the Sheahan well field, as well as leakage from the shallow to the Memphis aquifer through a hydrologic window in the upper Claiborne confining unit. The results of this work emphasize the utility of multiple investigative approaches in studies of groundwater flow to well fields, but they also illustrate the complexity of groundwater flow and groundwater vulnerability in a stressed water-supply aquifer system.

Aquifer storage and recovery (ASR) can provide a means of storing water for irrigation in agricultural areas where water availability is limited. A concern, however, is that the injected water may lead to a degradation of groundwater quality. In many agricultural areas, nitrate is a limiting factor. In the Umatilla Basin in north central Oregon, shallow alluvial groundwater with elevated nitrate-nitrogen of 9 mg/L is injected into the Columbia River Basalt Group (CRBG), a transmissive confined aquifer(s) with low natural recharge rates. Once recovery of the injected water begins, however, NO3 -N in the recovered water decreases quickly to +50, and correlate inversely with NO3 -N concentrations. This variation occurs in 3.0 mg/L. Similar to nitrate concentrations, TOC drops in the recovered water, consistent with this component contributing to the denitrification of nitrate during storage.

[1] The value of using environmental tracer profiles in aquitards to quantify fluid flux and to reveal information about palaeohydrology is largely unknown for parts of the world that were not glaciated during the Cenozoic. We present deep, continuous vertical profiles of aquitard pore water chloride concentration and δ2H/δ18O composition from the western margin of the Great Artesian Basin, Australia, where upward leakage is the dominant groundwater discharge mechanism. At the deeper of the two sites studied, the Cl− and δ2H profiles exhibit a distinctive S-shape, which we interpret as a shift in the upper concentration boundary condition over time. Numerical simulations are used to support an hypothesis that the shallow phreatic aquifer was more saline and more enriched in δ2H compared to current conditions prior to ∼120 ka, followed by an extended freshening phase from ∼120 to 20 ka, then a saline phase similar to current conditions for the last ∼20 ka. These timeframes correspond favorably with results of previous studies into the palaeohydrology of nearby playa Lake Eyre. At the shallower site, the tracer profiles decrease exponentially with depth. We explore several models for the evolution of these profiles and adopt one of long-term salt input at ground surface. At both sites, tracer concentrations for groundwater sampled from the underlying artesian aquifer provide conclusive evidence that recharge occurred within the last 10–20 ka. Chloride was a more useful tracer than δ2H in this study, primarily due to lack of recent glaciation in central Australia to provide a dynamic δ2H tracer signal.

[1] The age of groundwater, the time since the water recharged the subsurface, is a fundamental characteristic of groundwater that impacts diverse geologic processes and practical applications. The distribution of groundwater age depends on many factors including permeability, recharge rate, aquifer geometry, and topography. Seminal work simulated topography-driven regional groundwater flow with various topographies, localized high-permeability zones, and more recently with permeability decreasing with depth, but the role of layered aquifer systems which are common in both consolidated and unconsolidated sediments has not been systematically explored. Here we show that high age zones with predictable locations occur in layered geologic systems across a wide range of hydraulic gradients, basin geometries, and permeabilities. Numerical simulations of a generic three-layer aquifer system indicate that high age zones consistently form in the low-permeability layer near the middle of the basin. The zones of older groundwater result from low groundwater velocities in the low-permeability layer and the rejuvenation of the groundwater through mixing of different flow paths near discharge zones. The high age zones are not hydraulic stagnation points but are associated with areas of low velocity. Formation and location of zones of high groundwater ages in low-permeability units are important as these units are targeted for radioactive waste disposal and shale gas extraction. High age zones are also likely to affect geologic processes that depend on groundwater or solute fluxes and may serve as archives of past hydrological or climatological conditions.

A significant component of domestic demand for water of urban areas located in the Gangetic plains is met by heavy pumping of groundwater. The present study is focused on the Patna municipal area, inhabited by 17 million people and spanning over 134 km2, where entire urban water demand is catered from pumping by wells of various capacities and designs. The present study examines the nature of the aquifer system within the urban area, the temporal changes in the water/piezometric level and the recharge mechanism of the deeper aquifers. The aquifer system is made up of medium-to-coarse unconsolidated sand, lying under a ~40-m-thick predominantly argillaceous unit holding 8- to 13-m-thick localised sand layers and continues up to 220 m below ground. Groundwater occurs under semi-confined condition, with transmissivity of aquifers in 5,500–9,200 m2 day−1 range. Hydraulic head of the deeper aquifer remains in 9–19 m range below ground, in contrast to 1–9 m range of that of the upper aquitard zone. The estimated annual groundwater extraction from the deeper aquifer is ~212.0 million m3, which has created a decline of 3.9 m in the piezometric level of the deeper aquifer during the past 30 years. Unregulated construction of deep tube wells with mushrooming of apartment culture may further exacerbate the problem. The sand layers within the aquitard zone are experiencing an annual extraction of 14.5 million m3 and have exhibited stable water level trend for past one and half decades. This unit is recharged from monsoon rainfall, besides contribution from water supply pipe line leakage and seepage from unlined storm water drains.

In permafrost valleys, artesian wells often penetrate highly pressurized aquifers beneath confining subpermafrost. These wells must be quickly brought under control at installation, and heated through their operational life to prevent them from freezing in winter. However, water breakthrough of the permafrost barrier around the casing results in loss of control of the well. Seepage icing impacts to property and infrastructure can be catastrophic, and the costs to regain well control and mitigate damages high. Methods to regain control of artesian wells in permafrost are few and risky. A new method, cryogenic freezeback, was successfully used to mitigate an uncontrolled artesian well in a permafrost valley north of Fairbanks, Alaska. This paper documents the freezeback method, seepage and thermal analyses, and well abandonment and retrofit. Thermal monitoring results are presented to demonstrate the long-term effectiveness of the method.

In a coastal zone an understanding of the distance of the fresh water–salt water interface and its extension inland is important for prevention of sea water intrusion. In this article estimating methods are described for calculating the distance of a fresh water–salt water interface in a coastal confined aquifer based on the submarine fresh groundwater discharge. This groundwater discharge is controlled not only by the aquifer properties and hydraulic head difference, but also by the position of the fresh water–salt water interface in the coastal zone. A homogeneous and isotropic coastal confined aquifer is considered and fresh groundwater flow in the confined aquifer is thought to be at a steady state. Two observation wells at different distances in a profile perpendicular to the coastline are required in calculation of the distance of the interface toe in the coastal zone. Four coastal confined aquifers with horizontal and sloping confining beds and with varying thickness are also considered. Reasonable results are obtained when examples are used to illustrate the application of the methods. The methods require hydraulic head data at the two wells and thickness of the confined aquifers, but the hydraulic conductivity and fresh groundwater flow rate of the confined aquifers are not needed.

The Pleistocene Kimitsu aquifer was selected for examination of the relationship between groundwater age and chemical evolution of Ca(HCO3)2-type groundwater. For the most part, the aquifer is confined and composed mainly of quartz and feldspar with a small amount of calcite. The groundwater ages calculated by 14C were adjusted by using a carbon mass-balance method and corrected for effects of 14C diffusion. Groundwater ages in the Kimitsu aquifer vary from modern (upgradient) to approximately 2,400 years at 4.4 km from the edge of the recharge area. The 14C age was verified by groundwater velocity calculated from the hydraulic gradient and hydraulic conductivity. The confined groundwater evolved to Ca(HCO3)2-type around 50 years after recharge and this has been maintained for more than 8,300 years due to low chemical reactivity, derived from equilibrium with calcite, kaolinite and Ca-montmorillonite. In addition, high pH prevents the dissolution of Fe and Mn. Consequently, the rate of increase in electrical conductivity ranges from 10 to 30 μS/cm per 1,000 years. On the other hand, leakage from the deep region, which is recognized from high Cl– levels, causes remarkable increases in CH4 and HCO3 – concentrations, resulting in an apparent sulfidic zone at 500-m depth in most downgradient regions.

From about 1650 until 1200 BC Hattuša (pronounced Hattusha) was the capital of the Hittite Empire in central Asia Minor. On the steep terrain of today's ruined city lived and worked thousands of people whose homes, cattle, tools and places of worship had to be supplied with water. The question arose regarding how water was conveyed into the large-scale ponds in the urban area. The silted East Ponds (36,000 m3) and South Ponds (20,000 m3) have been excavated since the 1980s. A supply of the large volumes of water by a long pipeline from outside the city was repeatedly discussed. Due to the topographic, hydraulic and geo-hydrological conditions however, a long distance supply would have been uneconomic and also unnecessary. Still today, many willow fountains in the region are fed by artesian groundwater. It was therefore assumed that the ponds were cut into the slope aquifers and filled during the wet season. To verify this hypothesis, groundwater monitoring stations were installed in the autumn of 2009 directly uphill of the pond banks. Observed groundwater levels 2009–2011 are low in summer but rise above the former pond surfaces during winter. The Hittites used exfiltrating groundwater also in other reservoirs avoiding hefty and strongly varying surface inflows.

Defining aquifer permeability distribution accurately over large areas is often debated in hydrogeology. The operational efforts to calculate hydraulic conductivity with classical aquifer tests are significant; however, accurate knowledge of permeability areal distribution is fundamental both from a hydrogeological and a modeling standpoint. This paper presents an empirical relationship between the transmissivity (T) and the specific capacity (SC) values obtained from experimental aquifer and well tests. All experimental values were obtained from 50 mm wells in middle Venetian plain artesian gravel aquifers. Many other authors have presented empirical relationships between T and SC, but most are related to fissured/karst aquifers, and only a few concern alluvial porous aquifers. Analysis of the T vs. SC relationship standardized residuals shows that a linear relationship produces statistically significant normal residuals compared with an exponential relationship.

The first record of stable isotopes through a complete sequence of ice within an open-system pingo in northwestern Mongolia indicates a complex history of ice formation and pingo growth. A continuous section of ice 32 m long was cored through the centre of Mongot Pingo, and ice cores were analysed for stable isotopes and chemical composition. Two different stable isotope patterns in separate ice sections are identified: 1 open-system freezing and 2 semi-closed system (or closed system) freezing. Discharge measurements were observed in 2009 after drilling through pingo ice to artesian sub-pingo water and compared with data collected from the same pingo in 1968. Approximately 850–950 m3 of sub-pingo water discharged within 120 h during drilling in both 1968 and 2009, a volume equivalent to about 10 per cent of the current pingo ice volume. Between 1968 and 2009, permafrost (pingo ice) thickened by about 60 cm (1.46 cm per year), from 32.0 to 32.6 m, due to the decrease in sub-pingo artesian water pressure after water release from the 1968 drilling. The major mechanism for ice formation at this pingo is groundwater artesian pressure, though not continuously. Four major stages of pingo growth after 8790 yr BP are inferred. Copyright © 2013 John Wiley & Sons, Ltd.

Unplugged abandoned oil and gas wells in the Appalachian region can serve as conduits for the movement of waters impacted by fossil fuel extraction. Strontium isotope and geochemical analysis indicate that artesian discharges of water with high total dissolved solids (TDS) from a series of gas wells in western Pennsylvania result from the infiltration of acidic, low Fe (Fe < 10 mg/L) coal mine drainage (AMD) into shallow, siderite (iron carbonate)-cemented sandstone aquifers. The acidity from the AMD promotes dissolution of the carbonate, and metal- and sulfate-contaminated waters rise to the surface through compromised abandoned gas well casings. Strontium isotope mixing models suggest that neither upward migration of oil and gas brines from Devonian reservoirs associated with the wells nor dissolution of abundant nodular siderite present in the mine spoil through which recharge water percolates contribute significantly to the artesian gas well discharges. Natural Sr isotope composition can be a sensitive tool in the characterization of complex groundwater interactions and can be used to distinguish between inputs from deep and shallow contamination sources, as well as between groundwater and mineralogically similar but stratigraphically distinct rock units. This is of particular relevance to regions such as the Appalachian Basin, where a legacy of coal, oil and gas exploration is coupled with ongoing and future natural gas drilling into deep reservoirs.

Summary The bending of aquitard like a plate due to aquifer pumping and compression is often encountered in many practical problems of subsurface flow. This reaction will have large influence on the release of the volume of water from the aquifer, which is essential for the planning and management of groundwater resources in aquifers. However, the groundwater flow induced by pumping in a leaky aquifer system is often assumed that the total stress of aquifer maintains constant all the time and the mechanical behavior of the aquitard formation is negligible. Therefore, this paper devotes to the investigation of the effect of aquitard bending on the drawdown distribution in a leaky aquifer system, which is obviously of interest in groundwater hydrology. Based on the work of Wang et al. (2004) this study develops a mathematical model for investigating the impacts of aquitard bending and leakage rate on the drawdown of the confined aquifer due to a constant-rate pumping in the leaky aquifer system. This model contains three equations; two flow equations delineate the transient drawdown distributions in the aquitard and the confined aquifer, while the other describes the vertical displacement in response to the aquitard bending. For the case of no aquitard bending, this new solution can reduce to the Hantush Laplace-domain solution ( Hantush, 1960 ). On the other hand, this solution without the leakage effect can reduce to the time domain solution of Wang et al. (2004) . The results show that the aquifer drawdown is influenced by the bending effect at early time and by the leakage effect at late time. The results of sensitivity analysis indicate that the aquifer compaction is sensitive only at early time, causing less amount of water released from the pumped aquifer than that predicted by the traditional groundwater theory. The dimensionless drawdown is rather sensitive to aquitard’s hydraulic conductivity at late time. Additionally, both the hydraulic conductivity and thickness of the aquifer are the most sensitive parameters in influencing the predicted dimensionless drawdown.

Artesian springs are localized aquifer outlets that originate when pressurized ground water is allowed to rise to the surface. Computing artesian discharge directly is often subject to practical difficulties such as restricted accessibility, abundant vegetation or slow flow rates. These circumstances call for indirect approaches to quantify flow. This paper presents a method to estimate ground water discharge through an upwelling spring by means of a three-layer steady-state groundwater flow model. Model inputs include on-site measurements of vertical sediment permeability, sediment temperatures and hydraulic gradients. About 70 spring bed piezometers were used to carry out permeability tests within the spring sediments, as well as to quantify the hydraulic head at different depths below the discharge point. Sediment temperatures were measured at different depths and correlated to permeabilities in order to demonstrate the potential of temperature as a substitute for cumbersome slug tests. Results show that the spatial distribution of discharge through the spring bottom is highly heterogeneous, as sediment permeability varies by several orders of magnitude within centimetres. Sensitivity analyses imply that geostatistical interpolation is irrelevant to the results if field datasets come from a sufficiently high resolution of piezometric records. Copyright © 2013 John Wiley & Sons, Ltd.

Data for the Waimea Plains, New Zealand indicate that the lower confined groundwater aquifer is hydraulically homogeneous and that shallow groundwater levels inland are affected mostly by anthropogenic processes, while those near the coast are affected more by sea level variation. Analysis of long-term data for New Zealand indicates that sea level has increased continuously, but trends are not spatially uniform. Results from non-parametric trend analysis show that rising trends for groundwater levels are predominant in the shallow aquifer both inland on the Waimea Plains and, for recent years, near the coast, while decreasing trends are evident in the underlying confined aquifer near the coast. Groundwater level change in the shallow aquifer appears to be more affected by climate change than the lower confined aquifer. Correlation analysis indicated that groundwater levels are more affected by rainfall during the rainy season than the dry season and more influenced by rainfall inland than near the coast. Groundwater level declines in the lower confined aquifer near the coast, which has its major recharge area inland in the catchment, may be substantially affected by groundwater abstraction in inland areas as well as sea level variation, but there are little evidences of seawater intrusion. Meanwhile, groundwater recharge over the catchment area has great influence on rising groundwater levels in the shallow aquifer and its recharge is estimated to be 417.8 mm/year using chloride concentrations of precipitation and groundwater.

Few investigations have addressed the interaction between soil surface water regimes and raindrop impact on nutrient losses, especially under artesian seepage condition. A simulation study was conducted to examine the effects on nitrogen and phosphorus losses. Four soil surface water regimes were designed: free drainage, saturation with rainfall, artesian seepage without rainfall, and artesian seepage with rainfall. These water regimes were subjected to two surface treatments: with and without raindrop impact through placing nylon net over soil pan. The results showed saturation and seepage with rainfall conditions induced greater soil loss and nutrient losses than free drainage condition. Nutrient concentrations in runoff from artesian seepage without rainfall condition were 7.3–228.7 times those from free drainage condition. Nutrient losses by runoff from saturation and seepage with rainfall conditions increased by factors of 1.30–9.38 and 2.81–40.11 times, and the corresponding losses with eroded sediment by 1.37–7.67 and 1.75–9.0 times, respectively, relative to those from free drainage condition. Regardless of different soil surface water regimes, raindrop impact increased 20.90–94.0 % nutrient losses with eroded sediment by promoting soil loss, but it only significantly enhanced nutrient transport to runoff under free drainage condition.

The flowing fluid electric conductivity (FFEC) logging method is a well-logging technique that may be used to estimate flow rate, salinity, transmissivity, and hydraulic head of individual fractures or high-permeability zones intersected by a wellbore. Wellbore fluid is first replaced with fluid of a contrasting electric conductivity, then repeated FEC logging is done while the well is pumped. Zones where fluid flows into the wellbore show peaks in the FEC logs, which may be analyzed to infer inflow rate and salinity of the individual fractures. Conducting the procedure with two or more pumping rates (multi-rate FFEC logging) enables individual fracture transmissivity and hydraulic head to be determined. Here we describe the first application of the multi-rate FFEC logging method to an artesian well, using a 500-m well in fractured rock at Horonobe, Japan. An additional new factor at the site is the presence of regional groundwater flow, which heretofore has only been studied with synthetic data. FFEC logging was conducted for two different pumping rates. Several analysis techniques had to be adapted to account for the artesian nature of the well. The results were subsequently compared with independent salinity measurements and transmissivity and hydraulic head values obtained from packer tests in the same well. Despite non-ideal operating conditions, multi-rate FFEC logging successfully determined flow rate, salinity, and transmissivity of 17 conducting fractures intercepted by the logged section of the borehole, including two fractures with regional groundwater flow. Predictions of hydraulic head were less accurate, a not unexpected result in light of operational problems and the form of the equation for hydraulic head, which involves the difference between two uncertain quantities. This study illustrates the strengths and weaknesses of the multi-rate FFEC logging method applied to artesian wells. In conjunction with previous studies, it demonstrates the usefulness of the method for a broad range of conditions encountered in subsurface fractured rock.

Traditional aquifer vulnerability techniques primarily rely on spatial property data for a region and are limited by their ability to directly or indirectly assess flow and transport processes occurring from the surface to depth within an aquifer system. The main objective of this study was to investigate groundwater vulnerability in terms of aquifer interconnectivity and flow dynamics. A combination of stable isotopes, groundwater age-dating (radiocarbon), and geomorphic/geogenic spatial analyses was applied to a regional, highly developed coastal aquifer to explain the presence of nitrate at depth. The average δ(13) C value (-17.3 ± 2‰ VPDB, n = 27) is characteristic of groundwater originating from locally infiltrated precipitation through extensively cultivated soils. The average δ(18) O and δD values (-4.0 ± 0.1‰ VSMOW, n = 27; δD: -19.3 ± 1‰ VSMOW, n = 27, respectively) are similar to precipitation water derived from maritime sources feeding the region's surface water and groundwater. Stable and radioactive isotopes reveal significant mixing between shallow and deep aquifers due to high velocities, hydraulic connection, and input of local recharge water to depths. Groundwater overdevelopment enhances deeper and faster modern water downward flux, amplifying aquifer vulnerability. Therefore, aquifer vulnerability is a variable, dependent on the type and degree of stress conditions experienced by a groundwater system as well as the geospatial properties at the near surface.

The hydrogeological unit of Aguadulce (Campo de Dalias aquifers, SE Spain) has a complex geometry. This fact, together with a continuous rise in water demand due to intensive agriculture and tourism create problems for groundwater quantity and quality. In this paper classic geochemical tools managed by means of GIS software and geochemical simulations are combined to delineate, identify and locate the possible physicochemical processes acting in the Aguadulce groundwater. Two main aquifers can be distinguished: the carbonate or lower aquifer of Triassic age, and the calcodetritic or upper aquifer of Plio-Quaternary age. Groundwaters from the latter are more saline and, assuming all chlorinity originates from seawater intrusion, the seawater contribution to their composition would be up to 7%. Nevertheless the carbonate aquifer appears not to be homogeneous: it is compartmentalised into 4 zones where different processes explain the different groundwaters compositions. Zone 4 samples (E margin of the carbonate aquifer) resemble those of the Plio-Quaternary aquifer, where calcite precipitation, dolomite and gypsum dissolution and some cation exchange (water–rock interaction) together with seawater–freshwater mixing occur. In contrast, water–rock interaction predominates in zones 1 and 3 of the carbonate aquifer. Moreover, zone 2 samples, located between zones 1 and 3, are explained by water–rock interaction in addition to mixing with Plio-Quaternary aquifer waters. The combination of geochemical simulations with GIS and hydrogeochemical analyses has proven to be effective in identifying and locating the different physicochemical processes in the aquifer areas, thus improving understanding of hydrogeochemistry in complex aquifers.

Assessing recharge in unconfined fractured rock aquifers is a challenging task due to the discontinuous nature of this medium. In this study, a methodology is proposed based on an analytical interpretation of the regional hydraulic head profiles of an unconfined fractured rock aquifer, to determine its recharge. This calculation is conducted for a regional groundwater system based on a one-dimensional Dupuit-Forchheimer model in steady-state conditions that yields the value of the ratio of the aquifer recharge to the aquifer hydraulic conductivity. The approach is tested on a crystalline bedrock aquifer (Kenogami Uplands) of the Canadian Shield located in the Province of Quebec in Canada. The results show an average hydraulic conductivity of the aquifer of 4.3 × 10−7 m/s and a recharge equivalent to approximately 0.4% (3.5 mm/year) of precipitation. These results are in agreement with other studies conducted on similar crystalline aquifers in the Canadian Shield. Editor D. Koutsoyiannis Citation ...

The concentrations of chlorofluorocarbons (CFC-11, CFC-12 and CFC-113) and tritium (3H) content in groundwater were used to date groundwater age, delineate groundwater flow systems and estimate flow velocity in the Hohhot basin. The estimated young groundwater age is fallen in the bracket of 21 ~ 50 a and indicates the presence of two different age profiles and flow systems in the shallow groundwater system. Older age waters occur under the topographically low areas, where the aquifer is double-layer aquifer system consisting of shallow unconfined-semi-confined aquifer and deep confined aquifer. This reflects long flow paths associated with regional flow. Groundwater (range from 21 to 34 years) in the north piedmont and east hilly areas, where the aquifer is a single-layer aquifer consisting of alluvial fans, are typically younger than those in the low areas. The combination of CFCs dating with hydrogeological information indicates that both local and regional flow systems are present at the basin. The regional groundwater flow mainly flows from the north and east to the southwest, the local groundwater flow system occurs nearby the Hohhot city. The mean regional groundwater flow velocity of the shallow groundwater is estimated about 0.73 km/a. These findings can aid in refining hydrogeological conceptual model of the study area. Copyright © 2012 John Wiley & Sons, Ltd.

The northern Djeffara aquifer system is located in the southeast ofTunisiaand extends over an area of400 km2. This multilayer system of aquifers is essentially recharged by infiltration of rain and by groundwater of the Continental Inter-calaire aquifer, and occurs mainly at two levels between 0 and180 mdepth that belong to the Mio-Pliocene to form the aquifers. A combined hydrogeologic and isotopic investigation using several chemical and isotopic tracers’, i.e., major ions, δ18O, δ2H and tritium, was carried out in order to determine the sources of water recharge to the aquifer and the origin of salinity. The results of geochemical and isotopic studies show that the groundwater in the south of the study area represents a mixture of the Djeffara aquifer groundwater and locally infiltrates modern recharge. In the northern part, the groundwater which resembles that of the Sekhira aquifer originates from locally infiltrated rain and runoff. The salinity of the groundwater is caused by dissolution of evaporate rocks (gypsum and halite minerals) in the aquifer system. The stable isotopes data do not support the hypothesis of mixing with seawater.