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• Numerical modeling approach to estimate time-varying river to riverbed travel times. • Advection-dispersion equation with time-dependent coefficients. • Tikhonov regularization is used to avoid spurious parameter fluctuations. • Substantially sub-daily flux transients in riverbed sediments of three urban rivers. Assessing solute transport in riverbed sediments is important for quantifying the effective reactivity of hyporheic sediments and the magnitude of exchange flows between rivers and their river beds. A typical approach of estimating transport in riverbed sediments is by measuring natural tracers such as fluctuations of temperature or electrical conductivity (EC) and fitting models to them that assume time-independent travel time distributions, implying steady-state flow. Here, we use a transport parameterization that is based on the advection–dispersion equation (ADE) with coefficients that continuously vary in time. The ADE is solved numerically and its solution is fitted to measured EC time series using Bayesian parameter inference. A continuous function of model parameters is constructed by smoothly interpolating between point values with different temporal resolution, and Tikhonov regularization is used to avoid spurious parameter fluctuations. The approach is tested using EC time series synchronously measured in river water and hyporheic porewater of two urban rivers in Germany and one urban river in South Australia. For all datasets the goodness of fit was improved by introducing a time-dependent EC offset. Estimated porewater velocities were highly transient in three out of the four datasets with values increasing by up to a factor of six over the course of a day. Flux transients were likely related to both variations of hydraulic gradients along and spatial shifting of flow paths. Comparison to stationary, non-parametric deconvolution indicated that transient flow may induce multimodality in stationary travel time distributions. Given the high temporal dynamics of transport in the streambed sediments of the three investigated urban rivers, we envision that the presented model is also a valuable tool to improve the assessment of reactive transport in riverbed sediments. [ABSTRACT FROM AUTHOR]

Bottled natural mineral waters from an andesitic aquifer in Slovenia are enriched in magnesium (1.1 g/l), sulphate (2.2 g/l) and dissolved inorganic carbon (204 g/l). We analysed major ions, trace elements, tritium activity, 14C, δ18OH2O, δ2HH2O,δ13CDIC, gas composition and noble gases in six wells. In addition, 87Sr//86Sr, δ34SSO4 and δ11B were analysed here for the first time. Stable isotopes with δ18O = −11.97 to −10.30‰ and δ2H = −77.3 to −63.8 confirm meteoric origin. CO2 degassing is evident at three wells, causing the oxygen shift of about −1.3‰. Tritium activity was detectable only in the shallowest well, where the freshwater component was dated to the 1960s. δ13CDIC in five waters is −1.78 to + 1.33‰, typical of carbonate dissolution. Radiocarbon is low, 1.03–5.16 pMC. Chemical correction with bicarbonate concentration and δ13C correction methods gave best mean residence times, slightly longer than previously published. Sulphate has δ34S 26.6–28.9‰ and δ18O 8.9–11.1‰ due to dissolution of evaporites in carbonate rocks. Boron at concentrations of 1.2–6.1 mg/l has two origins: δ11B = 11.3–16.4‰ from hydrothermal alteration and δ11B = 26.6–31.7‰ from carbonate dissolution. Strontium at concentrations of 0.5–22.0 mg/l has 87Sr//86Sr, indicating three sources: 0.7106 for Miocene clastic rocks, 0.7082 for Triassic carbonates and 0.7070 for Lower Oligocene andesitic rocks. CO2 represents the majority of the dissolved (> 98.84 vol%) and separated gas (> 95.23 vol%). Methane is only found in two wells with a max. of 0.30 vol%. All waters show excess helium and 16–97% of mantle-derived helium. Since all show subsurface degassing, the paleo-infiltration temperature could not be calculated. [ABSTRACT FROM AUTHOR]

In the present work measurements of chloride concentrations were used to assess the variability of infiltration conditions and contributions of surface water and local groundwater to the discharge of wells at Krajkowo riverbank filtration site (western Poland). Tests were performed on samples from 26 wells located in a well gallery close to the River Warta. Due to higher chloride concentrations in river water in comparison with local groundwater, significant differences in concentrations in samples from individual wells were noted. In particular, lower chloride concentrations in 11 wells were recorded, which can be linked to the local occurrence of low-permeability deposits in the superficial zone; a locally higher degree of riverbed sediment clogging in the highly convex meandering zone, where strong erosion of the riverbed occurred, which in turn led to increased clogging; the occurrence of a more intensive groundwater inflow into the river valley due to water infiltration from a smaller river entering the River Warta valley, as well as unfavourable conditions for the infiltration of surface water to the lower part of the aquifer with a greater thickness. Differences in chloride concentrations observed were also used to quantify approximately river water contribution to the well production. The average contribution of the River Warta to the recharge of the entire well gallery was estimated at 59.8%.

Stable isotope compositions of carbon and nitrogen (expressed as δ13C and δ15N) from the European common cuttlefish (Sepia officinalis) were measured in order to evaluate the utility of using these natural tracers throughout the Northeast Atlantic Ocean and Mediterranean Sea (NEAO-MS). Mantle tissue was obtained from S. officinalis collected from 11 sampling locations spanning a wide geographical coverage in the NEAO-MS. Significant differences of both δ13C and δ15N values were found among S. officinalis samples relative to sampling location. δ13C values did not show any discernable spatial trends; however, a distinct pattern of lower δ15N values in the Mediterranean Sea relative to the NEAO existed. Mean δ15N values of S. officinalis in the Mediterranean Sea averaged 2.5‰ lower than conspecifics collected in the NEAO and showed a decreasing eastward trend within the Mediterranean Sea with the lowest values in the most eastern sampling locations. Results suggest δ15N may serve as a useful natural tracer for studies on the population structure of S. officinalis as well as other marine organisms throughout the NEAO-MS.

Sustainable water resources management plans require advanced instrumentation to measure accurately both the water velocity and the discharge of the aquatic bodies. An innovative way to achieve this goal is with the use of non-contact, cost-effective, and efficient image-based methods. A studied water surface can be captured by subsequent images while surface velocity can be estimated by the movement of tracers on the water’s surface. Various software have been developed in order to utilize such tracing algorithms and to monitor the surface velocity of fluids. The objective of this study was to present the current status of these software, describe the main parameters, and provide applied examples of image-based velocimetry application. To achieve this firstly, a comprehensive review was conducted that focused on the scientific publications that have utilized particle image and tracking velocimetry methods on water bodies. Secondly, the main scope of this research was to record and analyze these publications based on the software that were used. This paper presents 30 software with their main features and few of their application examples. This should help other researchers choose the appropriate image-based velocimetry software to measure water velocity and discharge based on the needs of their study. [ABSTRACT FROM AUTHOR]

A large drilling campaign has been conducted across sediments of the Tertiary Molasse Basin and the underlying Mesozoic in Northern Switzerland in the context of underground disposal of radioactive waste. The ~300-400 m thick Mesozoic low-permeability rock sequence of interest is located between the regional aquifers made of Malm limestone at the top and dolomite/limestone formations of the Muschelkalk at the bottom. Locally, water-conducting zones occur in Dogger marl/limestone (Hauptrogenstein) below the Malm and/or in Keuper sandstone/dolomite above the Muschelkalk aquifer. Here we report on the distribution of the natural tracers δ 2H and δ 18O in porewater and groundwater from eight new boreholes in three study areas. The distribution of these tracers is the result of hydrogeological processes acting in the past, and their analysis offers unique possibilities to decode large-scale transport processes. The large data set allows us to compare the variability of δ 18O and δ 2H vertically as well as laterally in the three areas (∼20 km apart) and in the 2–4 boreholes in each area (a few km apart). The eight isotope profiles show many similarities, but also distinct features that are related to the lateral variation of aquifer properties, tectonic setting and topography, and the geometry of the aquifer-aquitard systems. Boundaries of the profiles are typically given by groundwater in the Malm (one location in the Dogger) and Muschelkalk aquifer, and locally by water-conducting zones in the Keuper. Maximum isotope values in the central part of the profiles plot to the right of the GMWL (Global Meteoric Water Line) to different degrees, as do values in the Malm aquifer. Towards the Keuper aquifer (if present) and the Muschelkalk aquifer, the values decrease smoothly and sharply, respectively, and approach the GMWL. The sharp decrease towards the Muschelkalk aquifer indicates a change in the isotope signature in the recent past or is related to low porosity and low diffusivity values in adjacent anhydrite layers. The two tracers δ 2H and δ 18O show different trends in the more central parts (almost constant or decreasing with depth, respectively). These differences are very likely inherited from pre-Pleistocene processes, i.e., before the present-day signatures in the aquifers came into play. Transport simulations are used to narrow down the timing of changes in the aquifer signatures in the more recent past (10 ka to few Ma ago). The data presented here demonstrate that (1) lateral variability is limited, even though the low-permeability zones are found at different depths, meaning that transport regimes were similar over large times of the past, (2) the known lateral variability of the Keuper aquifer is confirmed by the porewater profiles, (3) diffusion can explain the observed profile shapes and (4) signatures in the central parts of the low-permeability zone are oldest in the sense that they are furthest away from the GMWL. • Eight porewater profiles of δ 18O and δ 2H show similarities, but also local features. • The latter are related to local differences in aquifer properties. • Signatures in the central part are oldest, i.e., furthest away from the GMWL. • The data indicate dominance of vertical diffusion across the Mesozoic rock sequence. • The natural tracers δ 18O and δ 2H in porewater are essential in tracking large-scale transport. [ABSTRACT FROM AUTHOR]

Groundwater contamination due to municipal solid waste landfills leachate is a serious environmental threat. During recent years, the use of stable isotopes as environmental tracers to identify groundwater contamination phenomena has found application to environmental engineering. Deuterium (2H) and oxygen (18O) isotopes have successfully used to identify groundwater contamination phenomena if submitted to interactions with municipal solid waste landfills leachate, with a significant organic amount. The paper shows two case studies, in central and southern Italy, where potential contamination phenomenon of groundwater under municipal solid waste landfills occurred. In both cases, isotope compositions referred to 2H and 18O highlight a δ2H enrichment for some groundwater samples taken in wells, located near leachate storage wells. The δ2H enrichment is probably caused by methanogenesis phenomena, during which the bacteria use preferentially the hydrogen “lighter” isotope (1H), and the remaining enriched the “heavier” isotope (2H). The study of the isotope composition variation, combined with the spatial trend of some analytes (Fe, Mn, Ni) concentrations, allowed to identify interaction phenomena between the municipal solid waste landfills leachate and groundwater in both case histories. Therefore, these results confirm the effectiveness of 2H isotopes application as environmental tracer of groundwater contamination phenomena due to mixing with municipal solid waste landfills leachate.

The Aconcagua river basin (Chile, 32 °S) has suffered the effects of the megadrought over the last decade. The severe snowfall deficiency drastically modified the water supply to the catchment headwaters. Despite the recognized snowmelt contribution to the basin, an unknown streamflow buffering effect is produced by glacial, periglacial and groundwater inputs, especially in dry periods. Hence, each type of water source was characterized and quantified for each season, through the combination of stable isotope and ionic analyses as natural water tracers. The δ18O and electric conductivity were identified as the key parameters for the differentiation of each water source. The use of these parameters in the stable isotope mixing “simmr” model revealed that snowmelt input accounted 52% in spring and only 22–36% during the rest of the year in the headwaters. While glacial supply contributed up to 34%, both groundwater and periglacial exhibited a remarkable contribution around 20% with some seasonal variations. Downstream, glacial contribution averaged 15–20%, groundwater seasonally increased up to 46%, and periglacial input was surprisingly high (i.e., 14–21%). The different water sources contribution quantification over time for the Aconcagua River reported in this work provides key information for water security in this territory.

Abstract: As water grows scarcer in semiarid and arid regions around the world, new tools are needed to quantify fluxes of water and chemicals between aquifers and rivers. In this study, we quantify the volumetric flux of subsurface water to a 24 km reach of the Brazos River, a lowland river that meanders through the Brazos River Alluvium Aquifer (BRAA), with 8 months of high‐frequency differential gaging measurements using fixed gaging stations. Subsurface discharge sources were determined using natural tracers and End‐Member Mixing Analysis (EMMA). During a 4 month river stage recession following a high stage event, subsurface discharge decreased from 50 m3/s to 0, releasing a total of 1.0 × 108 m3 of water. Subsurface discharge dried up even as the groundwater table at two locations in the BRAA located 300–500 m from the river remained ∼4 m higher than the river stage. Less than 4% of the water discharged from the subsurface during the prolonged recession period resembled the chemical fingerprint of the alluvial aquifer. Instead, the chemistry of this discharged water closely resembled high stage “event” river water. Together, these findings suggest that the river is well connected to rechargeable bank storage reservoirs but disconnected from the broader alluvial aquifer. The average width of discrete bank storage zones on each side of the river, identified with Electrical Resistivity Tomography (ERT), was approximately 1.5 km. In such highly compartmentalized aquifers, groundwater pumping is unlikely to impact the exchange between the river and the alluvium. [ABSTRACT FROM AUTHOR]

Forested wetlands dominated by black ash ( Fraxinus nigra) are currently threatened by the rapid expansion of the exotic emerald ash borer (EAB; Agrilus planipennis , Coleoptera: Buprestidae) in North America, and very little is known about the hydrology and ecology of black ash wetlands. The ecohydrological response of forested wetlands following a canopy disturbance has the potential to affect critical ecosystem services, and the degree of this effect may largely depend on the wetland's hydrogeological setting. The main objectives of this study were to characterize the hydrologic connectivity of uninfested black ash wetlands and evaluate the water table response to a simulated EAB disturbance. We hypothesized that black ash wetlands in northern Michigan were (a) seasonally connected to, and derived the majority of their water from groundwater, and (b) wetland water tables would be elevated following a simulated EAB infestation due to decreased transpiration with the loss of black ash. The results indicate that the black ash wetland sites received most of their water from groundwater discharge. Significantly smaller site transpiration fluxes and significantly slower rates of drawdown were detected during the growing season in the girdled and ash-cut treatment sites, and these responses collectively produced significantly elevated wetland water tables when compared to control sites in the latter portions of the growing season. However, the wetlands' strong connection with groundwater sources likely buffered the magnitude of hydrological responses associated with the loss of black ash from the landscape. [ABSTRACT FROM AUTHOR]

Copyright of Grundwasser 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 mean residence time (MRT) of karst groundwater in three mountainous catchments of the Western Himalaya was estimated using multiple approaches: the tritium method, the sine wave model and tracer tests. Water samples were collected from precipitation, glacier melt, streams and karst springs for δ2H and tritium analysis during 2012 and 2013. High tritium values were observed in winter precipitation and low values in summer precipitation. The variation of tritium in karst springs was similar to that of the streams, whereas glacier melt showed lower tritium values. The MRT of cold karst springs was shorter than that of warm karst springs. The tracer breakthrough curves (TBC) retrieved for different springs suggested a short travel time for groundwater and possibly conduit flow. Deterioration of water quality and variation in flux magnitude are the two main practical consequences of the short travel time of karst groundwater in the region.EDITOR D. KoutsoyiannisASSOCIATE EDITOR K. Heal [ABSTRACT FROM PUBLISHER]

Monitoring injected CO 2 in CCS sites using oxygen isotopes of water has been demonstrated in field and laboratory experiments. Here, we examine natural CO 2 -rich springs in the Daylesford-Hepburn region, South East Australia, which show water 18 O depletion compared to local precipitation. Geochemical modelling shows that water-rock reactions are unlikely to have a significant effect on the observed δ 18 O values, which can only be explained by isotopic exchange with CO 2 . The water δ 18 O shift can be used for monitoring CO 2 impact on shallow groundwater aquifers, provided that there is sufficient CO 2 and distinction between water and CO 2 δ 18 O values exists. [ABSTRACT FROM AUTHOR]

Os sedimentos oriundos de áreas agrícolas são importante fonte de poluentes para os ecossistemas aquáticos. Existem várias fontes de sedimentos na escala de uma bacia hidrográfica rural, como lavouras, pastagens, florestas, rede fluvial e estradas. Cada uma tem características diferentes na magnitude de contribuição e potencial de contaminação. Identificar a origem dos sedimentos é fundamental na compreensão da taxa de emissão de sedimentos e no manejo dos sedimentos erodidos na escala de bacia. Este trabalho foi desenvolvido com o propósito de identificar as principais fontes de sedimentos de duas bacias rurais de cabeceira no Sul do Brasil, as quais são representativas do sistema agrário e das características fisiográficas da região. A metodologia utiliza a comparação entre os solos de diferentes fontes e os sedimentos em suspensão, usando traçadores naturais. A análise discriminante encontrou um grupo de variáveis capazes de distinguir as fontes de sedimentos. Com base na análise de classificação, as contribuições relativas de cada fonte nas bacias de Agudo e Arvorezinha foram, respectivamente: lavouras (68,3 e 55,5 %), estradas (28,1 e 37,6 %) e rede fluvial (3,6 e 6,9 %). Os resultados mostram que, além da contribuição predominante das lavouras, as erosões nas estradas e na rede fluvial contribuem significativamente para produção total de sedimentos nas bacias, demonstrando a importância dessa informação para controle da erosão do solo e manejo dos sedimentos na escala de bacia hidrográfica.Sediments in agricultural areas represent a significant source of pollution of aquatic environments. There are many different sediment sources at the level of a rural catchment (e.g. crop fields, pastures, forests, river banks, and roads), with different magnitude of contribution and contaminant potential. The identification of the sediment origin is important to understand the sediment transport rate and the management of sediment eroded at the catchment scale. The goal of this work was to identify the main sediment sources of two rural headwater catchments in southern Brazil, representative of the regional agrarian system and physiographic characteristics. The methodology was based on a comparison between soils of different sources and the eroded sediments using natural tracers. A set of variables was found by the discriminant soil analysis to distinguish the sources. Based on the classification analysis, the relative contribution of each source to the eroded sediments in the Agudo and Arvorezinha catchments was, respectively: crop fields 68.3 and 55.5 %, roads 28.1 and 37.6 % and bank erosion 3.6 and 6.9 %. Results show that besides the major contribution coming from crop fields, erosion from roads and drainage represents a significant part of the total sediment. Such information is essential to control soil erosion and for sediment management at the catchment scale.

Within the scope of monitoring water percolation through the 100-m thick vadose zone in the area of Postojnska jama continuous measurements of precipitation were carried out on the surface, and continuous measurements of water flowandphysicalandchemicalparametersof selected water trickles were performed under the surface. Occasional samples of percolating waters were taken for the analysis of water oxygen isotope composition. An exponential model of groundwater flowwaselaborated,bymeansofwhichtheretentiontime of water in individual trickles was estimated. Modelled retention times of groundwater range from 2.5 months to over one year.

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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.)

Summary Base flow is the ground water contribution to stream flow. Many activities, such as water resource management, calibrating hydrological and climate models, and studies of basin hydrology, require good estimates of base flow. The base flow component of stream flow is usually determined by separating a stream hydrograph into two components, base flow and runoff. Analytical methods, mathematical functions or algorithms used to calculate base flow directly from discharge, are the most widely used base flow separation methods and are often used without calibration to basin or gage-specific parameters other than basin area. In this study, six analytical methods are compared to a mass balance method, the conductivity mass-balance (CMB) method. The base flow index (BFI) values for 35 stream gages are obtained from each of the seven methods with each gage having at least two consecutive years of specific conductance data and 30 years of continuous discharge data. BFI is cumulative base flow divided by cumulative total discharge over the period of record of analysis. The BFI value is dimensionless, and always varies from 0 to 1. Areas of basins used in this study range from 27 km 2 to 68,117 km 2 . BFI was first determined for the uncalibrated analytical methods. The parameters of each analytical method were then calibrated to produce BFI values as close to the CMB derived BFI values as possible. One of the methods, the power function ( aQ b + cQ ) method, is inherently calibrated and was not recalibrated. The uncalibrated analytical methods have an average correlation coefficient of 0.43 when compared to CMB-derived values, and an average correlation coefficient of 0.93 when calibrated with the CMB method. Once calibrated, the analytical methods can closely reproduce the base flow values of a mass balance method. Therefore, it is recommended that analytical methods be calibrated against tracer or mass balance methods. [ABSTRACT FROM AUTHOR]

This paper focuses on analysis of the time series of 7 Be and 210 Pb activity measured in moss, and the amount, as well as duration of precipitation, to gain a better understanding of the possible relationships between airborne radionuclide deposition and precipitation. Here we consider whether the amount of these airborne radionuclides in moss samples is a cumulative measure of radionuclide deposition and decay, and a new approach for analyses of the relationships between precipitation and moss activity concentrations is suggested. Through these analyses it was shown that comparison of cumulative activity measured at one location using moss, normalized by values of cumulative amount or duration of precipitation, showed different regimes of airborne radionuclide deposition. [ABSTRACT FROM AUTHOR]

The study of Orangeville Rise (USA, Indiana) and Hubelj (SW Slovenia) karst springs’storm hydrographs was the principal theme of our research. We used three and four component hydrograph separation techniques that were based on natural tracers. The resultsare similar in both study areas. They are in agreement with actual research hypothesis where it is supposed that an important part of the karst aquifer’s recharge arrives, rapidly and in concentrated form, from the epikrarst zone. The synthesis of data demonstrates thatepikarst water could occupy up to 50 % of the karst spring discharge during the precipitation event that should not be neglected in karst aquifer’s protection strategies.

The hydrogeological characteristics of some springs supplied by high-mountain carbonate rock aquifers, located in the south of Piedmont, in Italy, are presented in this work. The aquifers have different geological-structural conditions, including both deep and superficial karstification. Their catchment areas are located in a typical Alpine context at a high altitude of about 2000 m. These aquifers are ideal representations of the different hydrogeological situations that can be encountered in the high-altitude carbonate aquifers of the Mediterranean basin. It is first shown how the high-altitude zones present typical situations, in particular related to the climate, which control the infiltration processes to a great extent. Snowfall accumulates on the ground from November to April, often reaching remarkable thicknesses. The snow usually begins to melt in spring and continues to feed the aquifer for several months. This type of recharge is characterized by continuous daily variations caused by the typical thermal excursions. The hourly values are somewhat modest, but snowmelt lasts for a long time, beginning in the lower sectors and ending, after various months, in the higher areas. Abundant rainfall also occurs in the same period, and this contributes further to the aquifer supply. In the summer period, there is very little rainfall, but frequent storms. In autumn, abundant rainfall occurs and there are therefore short but relevant recharge events. It has been shown how the trend of the yearly flow of the high mountain springs is influenced to a great extent by the snowmelt processes and autumn rainfall. It has also been shown, by means of the annual hydrographs of the flow and the electric conductivity of the spring water, how the different examined aquifers are characterized by very different measured value trends, according to the characteristics of the aquifer. [ABSTRACT FROM AUTHOR]

Comparing high-resolution depth profiles of different naturally occurring environmental tracers in aquitards should yield consistent and perhaps complementary information about solute transport mechanisms and the timing of major hydrogeological and climatological events. This study evaluated whether deep, continuous profiles of aquitard pore water chloride concentration could provide further insight into the paleohydrology of the Williston Basin, Canada, than possible using high-resolution depth profiles of stable H/O isotopes of water ( δ18O, δ2H). Pore water samples were obtained from extracts of cores taken over 392 m of the thick Cretaceous shale aquitard. Water samples were also collected from wells installed in the underlying regional sandy aquifer (Mannville Group; 93 m thick) and from seepage inflows into potash mine shafts (to 825 m below ground). Numerical modeling of the 1-D vertical Cl− profile supported diffusion dominated solute transport in the shales. The modeling also showed a similar time frame for development of the Cl− profile prior to activation of the aquifer as determined from the δ18O profile (20-25 Ma); however, it provided a significantly longer and potentially better-constrained time frame for evolution of the profile during the activation phase of the aquifer (0.5-1 Ma). The dominant paleoevent reflected in present-day profiles of both tracers is the introduction of glaciogenic meteoric water to the Mannville aquifer underlying the shale during the Pleistocene. The source area of this water remains to be determined. [ABSTRACT FROM AUTHOR]

Highlights: [•] Natural tracers reveal interaction between esker aquifer and connected surface waters. [•] Groundwater flow systems are distinguishable with repeated seepage measurements. [•] The subsurface may act as a phosphate source for surface water bodies. [Copyright &y& Elsevier]

Summary: The Lez karst spring, the main perennial outlet of the Lez karst system in southern France, plays an important role in supplying drinking water to the Montpellier metropolitan region. In order to investigate the origin of groundwater, its circulation patterns, and to understand the connectivity and compartmentalization of a karst system, a multi-tracer approach was used to describe the hydrogeology of the Lez karst system. Groundwater samples were collected from Lez karst during a range of hydrologic conditions (between March 2006 and August 2009) and analyzed for major and trace elements, total organic carbon, fecal, and total coliform. During the first recharge event of autumn, highly-mineralized water was observed at Lez Spring during the studied years. Multiple parameters of water during this rise were monitored with a fine time-step in 2008. Discriminate Factorial Analyses revealed the existence of different water-types discharging at Lez Spring. During high stage periods, highly mineralized water initially discharges from the spring, followed by rapid infiltration water. This behavior suggests that hydrodynamics affect groundwater circulation by soliciting different endmembers. These characteristics were observed on a larger scale when monitoring three intermittent springs connected to Lez Spring. A detailed analysis using bivariate diagrams of major, trace elements and elemental ratios provided insight into different water origins, associated lithologies, and mineral-solution reactions related to hydrodynamic responses. From the five identified water-types, the two more contrasting ones are emphasized: the first one corresponds to the most geochemically evolved waters, issued from deep layers where evaporite chemical fingerprinting has been identified. They are characterized by high mineralization and high concentrations in Cl, Na, Mg, Li, B and Br elements, and high Sr/Ca, Mg/Ca and Cl/Br ratios. The second water-type corresponds to the most diluted (low mineralized) waters with high concentrations of NO3, bacteria, Total Organic Carbon (TOC), and represents the flux of rapid infiltration waters. This endmember underlines the vulnerability of the system to surface infiltration and anthropogenic contamination through the infiltration of water via sinkholes and well-developed fracture networks. [Copyright &y& Elsevier]

Abstract: Natural tracers (Cl− and stable water isotopes) in pore water of the Opalinus Clay and adjacent formations were studied in the motorway tunnel at Mont Russelin, Switzerland. The Opalinus Clay occurs in the core of an anticline which is cut by a complex system of thrust faults. Concentration profiles of natural tracers were taken from 17 boreholes along a 363m long section. Pore waters of drillcore samples were analysed with indirect and direct methods. The Cl− and stable water isotope distribution in the pore water shows a regular and well defined profile, with a conspicuous decrease towards the overlying Dogger limestone aquifer. The highest Cl− values (approximately 23,000mg/L) are found in the core of the anticline in Liassic claystones underlying the Opalinus Clay. To quantify the large-scale transport properties of the Opalinus Clay formation, a 2D transport model was constructed and used to reproduce the observed concentration profiles. The calculations indicate that the observed tracer distributions are consistent with diffusion as the dominant transport process. Groundwater flow in the overlying Dogger aquifer was initiated about 2–4Ma ago, which is long after the folding of the Jura Mountains and probably coincides with the exposure of the aquifer to freshwater recharge following continued erosion of the anticline. The calculations suggest that tracer distributions are controlled by 1) the timing of freshwater recharge in the overlying limestone aquifer, 2) the shape of the anticline and 3) the magnitude and the anisotropy ratio of diffusion coefficients. [ABSTRACT FROM AUTHOR]

Abstract: This case study demonstrates how natural heterogeneities of formation and injection waters can be applied to a number of production related applications, extending into the mature life of a reservoir. Break-through of injection water, identification and characterisation of production intervals and evaluation of responses to operational events are some of the possible applications during production. The Oseberg Øst oil field in the North Sea represents a complex situation with commingled production from all Brent Group formations. The Sr isotope composition is an excellent parameter for defining the natural baseline of formation water, with a good spatial resolution and vertical stratification. Aquifer water from the Utsira Formation is injected for pressure support, and reinjection of produced water has also been applied since the onset of water production. Utsira Formation water has high Mg, low Ba and low Sr content compared to the reservoir formation waters. Isotopic compositions (δD and 87Sr/86Sr) are also distinct. A non-reactive behaviour of Ba and Sr is verified from binary cross-plots and geochemical modelling. Break-through of injection water could be identified in five production wells based on Ba/Mg ratios. In one of the reservoir compartments (Beta Saddle), water injection points were changed after approximately three years. The Ba/Mg ratio could also identify the second injection water break-through in one of the wells due to an intermediate period of higher formation water content. Since the Sr content in the Utsira water is low, the 87Sr/86Sr ratio is a good natural tracer for formation water movements even at high ratios of injected water. In particular, the vertical stratification of 87Sr/86Sr is useful for quantifying production from different intervals in commingled wells. A methodology for using operational events, such as production allocations or shut-ins, for characterisation of production zones is discussed. [Copyright &y& Elsevier]

Abstract: The Jandia Isthmus (Fuerteventura, Canary Islands) is a complex aeolian system composed of Pliocene and Pleistocene marine deposits, which are partially covered of carbonate crusts, palaeosols and sand sheets. The area has been greatly influenced by climate changes during the Quaternary. Nowadays this area presents an arid landscape dominated by the aeolian processes. Grain size, mineralogical and micropalaeontological analyses have been carried out to identify the source area of these wind-blown materials, considering five possible sources: windward beaches, Pliocene dune cliffs, Upper Pleistocene aeolian deposits, carbonate crusts and basaltic outcrops. Each one of these analyses has been used to discriminate between the possible sources. Especially useful has been the use of foraminifera as natural tracers of the aeolian dynamics, as well as the application of the Rietveld method to quantify the mineralogical composition from the X-ray diffraction analysis (XRD). These techniques indicate that erosion of the Upper Pleistocene aeolian deposits — which partially cover the Isthmus surface — is the process that presently supplies most of the aeolian sediments that blow across the Isthmus. This study suggests the existence of extensive backshore surfaces westward of the present shoreline, during both the Pliocene and the Upper Pleistocene. This backshore was the original source area of aeolian materials transported by the Trade Winds, combined with the dust supply from Saharan desert. [Copyright &y& Elsevier]

Streamflow generation in the semiarid, seasonally snow-covered, and forested mountain catchments of the Valles Caldera, New Mexico, was investigated using chemical tracers. Samples were collected from snow, subsurface flow from hillslopes, and streamflow at Redondo and La Jara Creeks from December 2004 to July 2005. A new modeling procedure was developed by combining diagnostic tools of mixing models and end-member mixing analysis to evaluate the assumptions of mixing models. This procedure was successfully used to determine conservative chemical tracers, identify the number of end-members that contribute to streamflow, and evaluate eligibility of end-members. The results show that streamflow at Redondo Creek was generated from two end-members: lateral subsurface flow (∼80%) and thermal meteoric water (∼20%). Streamflow at La Jara Creek was primarily from lateral subsurface flow alone. Overland flow of snowmelt was not a significant contributor to streamflow in either catchment. Lateral subsurface flow is an important process of streamflow generation in semiarid environments in the southwest United States and should play a critical role in regulating biogeochemical cycles. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the application of stable carbon isotope ratios as natural tracers in hydrocarbon reservoirs. Detailed mapping of hydrocarbon composition from closely spaced mud gas samples taken during drilling of horizontal production wells allows for the identification of reservoir compartmentalisation. This applies to reservoirs where fluid heterogeneities exist as a result of filling history or post accumulation hydrocarbon alteration. Case examples assessing fault seal properties are provided. An additional application of the methodology presented is in the detection of subtle spatial variations in reservoir rock quality that may have an influence on fluid flow within the reservoir. In several cases where fluid heterogeneities were detected in horizontal wells, subsequent time-lapse sampling of produced gas and stable carbon isotope measurements of these samples gave means for production allocation. The identification of lost production permitted the identification of an infill well target, and resulted in increased oil recovery by the drilling of a new production well. The use of gas isotopes in the evaluation of reservoir fluid heterogeneities and as natural tracers in the monitoring of reservoir fluids has proved useful in the understanding of reservoir connectivity and fluid flow. The work processes described give valuable insights and help improve reservoir management. [Copyright &y& Elsevier]

The role of an epikarst zone in the karst aquifer hydraulic behaviour was brought into focus in our studies referring to the catchment area of the Hubelj spring (SW Slovenia). This study points out the significance of effects of the fast preferential flow—epiflow, which is the main factor controlling solute/contaminant transport towards the aquifer saturated zone. The so-called epikarstic hypothesis is verified on the basis of the most significant research results that are supported by the most important findings from the literature. [ABSTRACT FROM AUTHOR]

The acidic discharge from Cement Creek, containing elevated concentrations of dissolved metals and sulphate, mixed with the circumneutral-pH Animas River over a several hundred metre reach (mixing zone) near Silverton, CO. during this study. Differences in concentrations of Ca, Mg, Si, Sr, and SO42- between the creek and the river were sufficiently large for these analytes to be used as natural tracers in the mixing zone. In addition, a sodium chloride (NaCl) tracer was injected into Cement Creek, which provided a Cl- 'reference' tracer in the mixing zone. Conservative transport of the dissolved metals and sulphate through the mixing zone was verified by mass balances and by linear mixing plots relative to the injected reference tracer. At each of seven sites in the mixing zone, five samples were collected at evenly spaced increments of the observed across-channel gradients, as determined by specific conductance. This created sets of samples that adequately covered the ranges of mixtures (mixing ratios, in terms of the fraction of Animas River water, %AR). Concentrations measured in each mixing zone sample and in the upstream Animas River and Cement Creek were used to compute %AR for the reference and natural tracers. Values of %AR from natural tracers generally showed good agreement with values from the reference tracer, but variability in discharge and end-member concentrations and analytical errors contributed to unexpected outlier values for both injected and natural tracers. The median value (MV) %AR (calculated from all of the tracers) reduced scatter in the mixing plots for the dissolved metals, indicating that the MV estimate reduced the effects of various potential errors that could affect any tracer. [ABSTRACT FROM AUTHOR]

Abstract: The origin of chloride-rich karstic spring waters representative of the Languedoc-Roussillon region has been investigated with a hydrochemical approach. To this end, the major and trace elements most often used in the study of saline environments have been considered (Cl, SO4, Br, B, Li). This study allowed distinguishing the different end-members of the various chloride-rich karstic spring waters (evaporitic, marine, geothermal). Associated with the Cl, Br and B contents, the Li/SO4 ratio appeared as a relevant tracer for the determination of the origin of lithium and by extension of the considered waters. To cite this article: O. Hébrard et al., C. R. Geoscience 338 (2006). [Copyright &y& Elsevier]

Abstract: Although footprint modelling has become an important and widely used tool in micrometeorology, the validation of existing models remains an outstanding problem. This study presents experimental approaches using natural tracer measurements to evaluate the performance of footprint models, which are intended to provide an inexpensive and practical alternative to footprint evaluation experiments releasing artificial trace gases. The approaches tested and discussed here are based on either eddy-covariance measurement complexes or small aperture scintillometers operated during field scale experiments in an area of well-defined heterogeneity. We tested two different footprint validation approaches based on natural tracer measurements: firstly, a comparison of measured flux differences and modelled land use differences for pairs of measurement positions and secondly, a correlation analysis between measured and modelled quantities using reference measurements. We tested these footprint validation approaches on two different footprint models, an analytical flux source area model and a forward Lagrangian stochastic trajectory model. For the test we utilised measurements from an intensive field scale measurement campaign from summer 2002 instead of performing a new experiment to derive the required data set. The results of this study clearly demonstrate that the two approaches tested here based on natural tracers provide a valuable tool for footprint validation purposes. The first approach highlighted qualitatively the agreement between flux differences and differences in the land use of the surrounding terrain determined by footprint calculations, while the second approach, the correlation analysis between measured and modelled quantities, also allowed the comparison of the two footprint models on a quantitative basis. However, due to experimental shortcomings of the employed data set, additional scatter compromised the accuracy of the results; therefore, no significant differences between both footprint models could be found in this study. [Copyright &y& Elsevier]

Abstract: This article introduces a methodology for integrating geochemical data in reservoir simulations to improve hydrocarbon reservoir models. The method exploits routine measurements of naturally existing inorganic ion concentration in hydrocarbon reservoir production wells, and uses the ions as non-partitioning water tracers. The methodology is demonstrated on a North Sea field case, using the field''s reservoir model, together with geochemical information (SO4 2−, Mg2+, K+, Ba2+, Sr2+, Ca2+ and Cl− concentrations) from the field''s producers. Based on the dataset, some of the ions are shown to behave almost as ideal seawater tracers, i.e. without sorption to the matrix, ion exchange with the matrix or scale formation with other ions in the formation water. Moreover, the dataset shows that ion concentrations in pure formation water vary according to formation. This information can be used to allocate produced water to specific water-producing zones in commingled production. Based on an evaluation of the available data, one inorganic component, SO4 2−, is used as a natural seawater tracer. Introducing SO4 2− as a natural tracer in a tracer simulation has revealed a potential for improvements of the reservoir model. By tracking the injected seawater it was possible to identify underestimated fault lengths in the reservoir model. The demonstration confirms that geochemical data are valuable additional information for reservoir characterization, and shows that integration of geochemical data into reservoir simulation procedures can improve reservoir simulation models. [Copyright &y& Elsevier]

We introduce the concepts of a novel approach that allows for the quantification of infiltrating non-polluted waters by a combined analysis of time series of pollutant concentrations and discharged wastewater volume. The methodology is based on the use of automated sensors for the recording of the pollutant concentrations. This provides time series in a high temporal resolution that are suitable for a detailed data analysis and discussion on the underlying assumptions. The procedure is demonstrated on two examples from recent measurement campaigns in Switzerland. [ABSTRACT FROM AUTHOR]