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Over the past decades, fractured and karst groundwater systems have been studied intensively due to their high vulnerability to nitrate (NO3−) contamination, yet nitrogen (N) turnover processes within the recharge area are still poorly understood. This study investigated the role of the karstified recharge area in NO3− transfer and turnover by combining isotopic analysis of NO3− and nitrite (NO2−) with time series data of hydraulic heads and specific electrical conductivity from groundwater monitoring wells and a karstic spring in Germany. A large spatial variability of groundwater NO3− concentrations (0.1–0.8 mM) was observed, which cannot be explained solely by agricultural land use. Natural-abundance N and O isotope measurements of NO3− (δ15N and δ18O) confirm that NO3− derives mainly from manure or fertilizer applications. Fractional N elimination by denitrification is indicated by relatively high δ15N- and δ18O-NO3− values, elevated NO2− concentrations (0.05–0.14 mM), and δ15N-NO2− values that were systematically lower than the corresponding values of δ15N-NO3−. Hydraulic and chemical response patterns of groundwater wells suggest that rain events result in the displacement of water from transient storage compartments such as the epikarst or the fissure network of the phreatic zone. Although O2 levels of the investigated groundwaters were close to saturation, local denitrification might be promoted in microoxic or anoxic niches formed in the ferrous iron-bearing carbonate rock formations. The results revealed that (temporarily) saturated fissure networks in the phreatic zone and the epikarst may play an important role in N turnover during the recharge of fractured aquifers.

Following a brief summary of some fundamentals in carbonate sedimentology (sedimentary petrography) that highlights the significance of organic matter, some examples of biocrystals in carbonate grains/particles, such as bioclasts or ooids, are provided as an introductory chapter to a discussion on gravitational cements versus endostromatolites. The gravitational cements, either marine (fibrous) or continental (dog-tooth), are made of hyaline (i.e., translucent) sparitic crystals whereas endostromatolites are made of colored sparitic crystals and/or micrite. Gravitational cements forms in the vadose zone whereas endostromatolites grow in small rock cavities in the marine phreatic zone. As such the latter can grow centripetally in all directions (not only downward).

Meteoric and mixing-zone diagenesis can dramatically alter the geochemical signatures of shallow marine carbonates. Most preserved pre-Cretaceous carbonates were deposited in shallow marine environments and thus may have been susceptible to meteoric and mixing-zone diagenesis. However, a quantitative understanding of how the geochemical composition of carbonates changes during diagenesis still requires further development. Here, we present a new two-dimensional (2D) reactive transport model coupled with a 2D coastal hydrology model to simulate carbonate diagenesis and provide insights into its impact on the isotopic and elemental compositions of carbonates in the geological record. Using this model, we have simulated the stratigraphic trends and relationship between isotopic records (for example, δ13C and δ18O values) observed in modern (Recent-Miocene) sections where the impact of meteoric diagenesis has been clearly characterized. Our model can also reproduce anomalous Neoproterozoic carbonate geochemical profiles where the effects of meteoric diagenesis have been debated. Further, our model indicates that linear carbonate C-O isotope co-variations can either be generated in the mixing zone between freshwater and marine pore waters, or in the freshwater phreatic zone with a downward decrease in recrystallization (with no net carbonate dissolution or precipitation) rate. In addition, numerous processes were observed to decouple δ18Ocarb values from other isotopic and elemental signatures during carbonate diagenesis, indicating that a lack of linear correlation between δ18Ocarb values and other geochemical variables does not necessarily suggest limited meteoric alteration. Sensitivity analyses show that the steady-state timescale is controlled by compositional differences between fluid endmembers, the calcite-water element distribution coefficient, the recrystallization rate, porosity, and the groundwater discharge rate. Given that reactive transport models have proven to be powerful theoretical tools in many disciplines of Earth sciences, our hope is that this model will promote a more quantitative understanding of meteoric and mixing zone diagenesis of marine carbonates.

The Classical Karst (sensu stricto) represents a complex hydro-geomorphological unit as well as one of the best-known karstic systems in the world. For this reason, it was selected as a model area both for applied research and for the conservation of its highly diverse subterranean fauna. With this paper, we aim to provide an overview of groundwater fauna in the phreatic zone of the Classical Karst aquifer, based on all published material along with new surveys, and search for patterns of species distribution within hydrogeological subunits, with a focus on the potential use of species as tracers of hydrological connections and groundwater flowpaths. The Classical Karst, with an area of approximately 750 km2, and adjacent to alluvial and flysch areas provides habitats for 83 stygobionts (accompanied by 16 stygophiles) and is one of the richest hotspots for groundwater fauna across the globe. The rate of endemism within the area is very high (around 50%). Multivariate statistical analyses revealed the faunal turnover between hydrogeological subunits, as well as the effect of water flow regime. Our approach, using species turnover and the species indicator value, allowed us to recognise groups of indicator species, which can be considered as descriptors of aquifer type and habitat structure, as well as water flow regime and groundwater flowpaths.

Aquifers with time variant catchment boundaries, regional flows, and inflows from surface streams and accumulations are common in karst areas. Due to the lack of reliable methods for determination of water balance in the phreatic zone of such aquifers, groundwater recharge estimation is a challenge task. This paper introduces a new method for estimation of groundwater recharge in karst – the so-called partial correlation method (PCM). The basic hypothesis is that the groundwater recharge rates can be determined from the time series of precipitation, air temperature, relative humidity, and spring discharge, by using a partial cross-correlation function as objective function. Following this hypothesis, a simple conceptual model of water balance in the soil cover, epikarst and vadose zone is developed, and an objective function for estimation of the optimal value of parameter of this model is proposed. PCM is applied on the catchment of Žrnovnica Spring located in the Dinaric karst area of Croatia. The results of application are compared with the results of previous studies, as well as with the results obtained by five empirical models that have been used for estimation of groundwater recharge in the Mediterranean karst. The effective infiltration coefficients obtained by PCM for the Žrnovnica Spring are generally in accordance with the previously published ones.

We report preliminary results of a field study of the natural discharge styles of a Pleistocene karst aquifer in uplifted Cenozoic coral-algal reef and lagoonal limestone. Discharge in deeply enscalloped embayments appears to be characterized by closely distributed springs and seeps that occur along the entire length of the bays. Along the rocky, cliff-dominated coastlines, discharge appears to be dominated by flow from cavernous openings and solution-widened fractures at the waterline, with occasional submarine springs. Documentation of the discharge styles and relative contributions of observed discharge points to total discharge, along with separate data on aquifer lithology and hydrology, provide bases for inferences regarding the degree and style of karst development. Observations from this study are consistent with separate evidence for a mixed karst in which flow may be relatively diffuse in the current phreatic zone, even though flow in the vadose zone has been observed to be strongly conduit-controlled in some areas. The following conclusions appear defensible on the basis of observations to date: (1) Discharge on embayed beaches is more evenly distributed than along the cliff-dominated coast. (2) The aquifer can best be described as mixed karst, and significant local variation can be expected in aquifer characteristics.

Shaft development can be documented on the basis of comparative studies of specific shaft lengths and shaft patterns. We calculated the specific length of shafts and the average specific shaft length of the shafts in some karst areas and we investigated the relation between the altitude of shaft floors and the specific shaft length. Taking the registered specific shaft lengths and the shaft patterns into consideration, it can be stated that some parts of the shafts developed paragenetically in the studied karst areas. In the Bakony Region, this was caused by surface water influx, rise of karst water level, and their simultaneous effect. As a result, shaft systems, bifurcating shafts and storeyed shafts developed. On glaciokarst areas, shafts may constitute a system with phreatic passages: either because a phreatic envi ronment developed in the vadose zone due to the permanent impoundment of karst water or because a phreatic passage got into the vadose zone since the karst became elevated. On the studied karst areas, the following shaft development types are distinguished: glacial-high mountain surface flood development type (1), glacial-high mountain karst water and surface flood development type (2), glacial karst water and surface flood later phreatic development type (3), shaft with a passage that got into the vadose zone (4).

Increasing background salinity in watersheds has largely been attributed to road salt retention in groundwaters due to their long residence times. However, laboratory studies demonstrate that soils temporarily store salts, either in porewater or adsorbed onto particles. Field studies of road salt retention in soils are nevertheless rare, and mechanisms of salt transport across multiple hydrological reservoirs (e.g., from soil to groundwater) are unknown. Thus, we collected roadside soil porewater and karst spring water weekly for ~1.5 yr to determine salt transport through the vadose zone into the phreatic zone. We observed dual retention mechanisms of sodium (Na+) and chloride (Cl−) in soils due to slow porewater movement, causing ion movement through the soil as slow as 1.3 cm/day, and cation exchange processes, leading to initial Na+ retention followed by later release months after application. Cation exchange processes also caused base cation loss from exchange sites into mobile porewater. Rapid Na+ and Cl− delivery to groundwater occurred through karst conduits during the winter. However, elevated background levels of salt ions in groundwater during the non-salting months indicated accumulation in the catchment due to slower porewater flow in the soil and rock matrix and delayed Na+ release from soil exchange sites.

The new railway line between Divača and Koper/Capodistria in south-western Slovenia is being built, a part of which crosses the southern outskirts of the Classical Karst plateaux. It will run through two tunnels, the northern tunnel T1 (6.7 km long) and the southern T2 (6 km long), which partially cross karst aquifer system. A multi-tracer test with injections of fluorescent dyes uranine and naphthionate, bypassing the karst vadose zone, was carried out to define the directions and dynamics of the underground water flow. The main goals were better understanding of the complex hydrogeological conditions in the area and assessment of possible environmental impacts on the nearby water sources. With tracing of uranine injected into a nearby cave stream, the direction of flow from the northern T1 tunnel mainly towards the Reka-Timavo aquifer system and further towards the Timava/Timavo springs was proved. The peak velocities, as determined from the peaks of the tracer breakthrough curves, range from 29 m/h to 36 m/h. Through the wider and well-connected conduits of the Reka-Timavo system, the peak velocities can reach up to 88 m/h. The recovery of uranine in an intermediate cave, i.e., Jama 1 v Kanjaducah, amounted to approximately 74 %. The northern section of the southern T2 tunnel is a part of a wider bifurcation zone between the Osapska Reka and the Boljunec/Bagnoli springs, where peak flow velocities between 10 and 13 m/h have been determined by tracing of naphthionate injected into a borehole located in the line of the planned tunnel. It has been estimated that about 25 % of the injected naphthionate flew out through the Osapska Reka spring and about 5 % through the Boljunec/ Bagnoli springs. Based on this research, proper monitoring of any potential negative impacts of the new railway line will be made possible. The study presents an approach to better planning of hazard control of traffic routes in complex and highly karstified rock settings.

Karst aquifers are hydraulic structures where dissolution conduits dictate complex spatial and temporal flow patterns. These aquifers are vertically divided into phreatic, epiphreatic and vadose zones. While the phreatic zone is permanently saturated, providing the major contribution to base flow, most of the flood event water is transferred through the epiphreatic zone. The spatial distribution of conduits within karst aquifers is largely unknown. The only technique giving accurate results is direct human exploration, although some limited information can be obtained from hydrograph analyses in springs and wells, through hydraulic tomography and by geophysical surveys.

The Lower Paleozoic gas reservoirs in central Sulige gas field are mainly accumulated in Ordovician ancient weathering crust karst carbonate reservoirs, and they are especially rich in the upper assemblage of Ordovician Majiagou formation (Ma51–Ma54 sub-members). However, the spatial distribution of gas is unclear yet because of the different denudation degree and uneven development of paleokarstification. This paper mainly focuses on the characteristics of paleogeomorphology and paleokarstification and their impact on natural gas accumulation. Geological stratifying has been done based on the observation of cores and thin sections, and the analysis of drilling, logging and seismic data. The paleogeologic map of pre-carboniferous was depicted according to the ancient weathering crust outcropped strata. Paleogeomorphology reconstruction is based on a comprehensive method combining the moulage method with the residual thickness method. Result indicates that the paleogeomorphology can be divided into western karst highland and eastern karst slope in the area investigated, and the denudation degree of ancient weathering crust in the west is more serious than that in the east. The karst highland can be divided into remnant hill and depression while the karst slope can be divided into gentle hill and shallow depression in detail. Paleokarst section can be vertically divided into epikarstic zone, vertical vadose zone, horizontal phreatic zone and deep slow flow zone based on the analysis of paleokarst identification mark and vertical dissection of single well. By analyzing the relationship between paleokarst characteristics and production data, the study shows that paleogeomorphology and paleokarstification have a significant control on nature gas accumulation and distribution. Gentle hills on karst slope are expected to be the most favorable areas for reservoirs horizontally, horizontal phreatic zone is more advantageous vertically, and second the vertical vadose zone.

The meteoric diagenetic environment has multiphase characteristic, but the scales of the reservoirs in different meteoric diagenetic environments have been rarely considered. On the basis of geological and well-logging analyses, three distinct phases of the meteoric diagenetic process were observed in the Ordovician of the Jingxi area in Ordos Basin, China. The phreatic zone formed in the first phase is partially preserved, whereas those formed in the second and third phases are completely retained. Strata in the western (close to the Central Uplift Belt) and eastern parts underwent bedding-parallel meteoric dissolution and cross-layer meteoric dissolution, respectively. The distributions of the dissolution formation thicknesses in two successive phases of the meteoric diagenetic process exhibit complementarity at the same positions in the plane. The favorable reservoirs at the top of the Ordovician are mainly distributed in the western parts. The second phase of the meteoric diagenetic process is most conducive to the formation of carbonate reservoirs. By dividing and comparing the multiphases of the meteoric diagenetic environment of carbonates, the favorable karst reservoirs can be predicted in each phase.

Most bauxite in China is located upon the karst surface, yet the relation between karstification process and bauxite formation is barely known. Here we discuss how the relation affects the karst and bauxite evolution through analyzing distributions of orebody parameters from 9,007 exploration wells (434 orebodies) in western Guangxi, South China block. In high-elevation karst terrain dominated by peaks, orebodies have greater average thickness, lower Al2O3 and higher Fe2O3T than those in low-elevation region dominated by depressions. Principal component and multifractal analyses show that the Al2O3, Fe2O3T and LOI and the orebody thickness, determined by depression geometry, have more even distributions in high-elevation terrain. This explains that the interaction between the oxidized, alkaline water in karst surface and the ferrous clay minerals that released H+ during bauxite secondary weathering was more intensive in high-elevation terrain than in low-elevation one. The interaction with self-organized nature is considered responsible for the even development of karstic depressions and bauxite orebody thicknesses in high-elevation terrain. In comparison, SiO2 distribution is more even in low-elevation terrain, where connected depressions near the phreatic zone facilitated SiO2 mobilization and even distribution.

This study focuses on the impact of surface reservoirs (fish ponds) on a multi aquifer coastal system, and the relation between the aquifer and the sea. The study was conducted in an Israeli Mediterranean coastal aquifer, which includes a sandy phreatic unit and two confined calcareous sandstone units. The geological description is based on 52 wells, from which 33 samples were collected for stable isotope analysis and 25 samples for organic and inorganic parameters. Hydraulic head and chemical measurements suggest that there is an hydraulic connection between the fish ponds above the aquifer and the phreatic unit, whereas the connection with the confined units is very limited. The phreatic unit is characterized by a low concentration of oxygen and high concentrations of ammonium and phosphate, while the confined units are characterized by higher oxygen and much lower ammonium and phosphate concentrations. Organic matter fluorescence was found to be a tool to distinguish the contribution of the pond waters, whereby a pond water signature (characterized by proteinaceous (tryptophan-like) and typical humic-matter fluorescence) was found in the phreatic aquifer. The phreatic unit is also isotopically enriched, similar to pond waters, with δ18O of −1‰ and δD of −4.6‰, indicating enhanced evaporation of the pond water before infiltration, whereas there is a depleted isotopic composition in the confined units (δ18O = −4.3‰, δD = −20.4‰), which are also OM-poor. The Phreeqc model was used for quantitative calculation of the effect of pond losses on the different units. The Dissolved Inorganic Nitrogen (DIN) in the upper unit increases downstream from the ponds toward the sea, probably due to organic matter degradation, suggesting contribution of DIN from shallow groundwater flow to the sea. 87Sr/86Sr and Mg/Ca in the brackish and saline groundwater of the lower confined units increase toward seawater value, suggesting that the salinization process in the region is connected to seawater intrusion and not to old brine from the underlying Cretaceous aquitard.

One of the greatest challenges in critical zone studies is to document the moisture dynamics, water flux, and solute chemistry of the unsaturated, fractured and weathered bedrock that lies between the soil and groundwater table. The central impediment to quantifying this component of the subsurface is the difficulty associated with direct observations. Here, we report solute chemistry as a function of depth collected over a full year across the shale-derived vadose zone of the Eel River Critical Zone Observatory using a set of novel sub-horizontal wellbores, referred to as the vadose zone monitoring system. The results of this first geochemical glimpse into the deep vadose zone indicate a dynamic temporal and depth-resolved structure. Major cation concentrations reflect seasonal changes in precipitation and water saturation, and normalized ratios span the full range of values reported for the world’s largest rivers.

Understanding the dynamics and mechanisms of soil water movement and solute transport is essential for accurately estimating recharge rates and evaluating the impacts of agricultural activities on groundwater resources. In a thick vadose zone (0-15 m) under irrigated cropland in the piedmont region of the North China Plain, soil water content, matric potential and solute concentrations were measured. Based on these data, the dynamics of soil water and solutes were analysed to investigate the mechanisms of soil water and solute transport. The study showed that the 0-15 m vadose zone can be divided into three layers: an infiltration and evaporation layer (0-2 m), an unsteady infiltration layer (2-6 m) and a quasi-steady infiltration layer (6-15 m). The chloride, nitrate and sulphate concentrations all showed greater variations in the upper soil layer (0-1 m) compared to values in the deep vadose zone (below 2 m). The average concentrations of these three anions in the deep vadose zone varied insignificantly with depth and approached values of 125, 242 and 116 mg/L. The accumulated chloride, sulphate and nitrate was 2179 ± 113, 1760 ± 383 and 4074 ± 421 kg/ha, respectively. The soil water potential and solute concentrations indicated that uniform flow and preferential flow both occurred in the deep vadose zone, and uniform flow was the dominant mechanism of soil water movement in this study. The piston-like flow velocity of solute transport was 1.14 m/yr, and the average value of calculated leached nitrate nitrogen was 107 kg/ha∙yr below the root zone. The results can be used to better understand recharge processes and improve groundwater resources management. This article is protected by copyright. All rights reserved.

Caves reaching the (epi)phreatic zone may provide the only access to groundwater in the internal parts of karst aquifers. Modern instruments enable unattended high frequency measurements of groundwater parameters in such caves. A network of distributed observation points may give new information on temporal and spatial pattern of groundwater flow. Such network, recording water level, temperature and specific electrical conductivity was established in all major ponors and active water caves of the karst aquifer between Planinsko Polje and springs of the Ljubljanica River, Slovenia. Up to three and a half years long records were analysed in view of available and relevant geological, speleological, meteorological and hydrological information, and basic hydraulic principles of the epiphreatic flow. The result of the interpretation were models of possible conduit networks of the three main flow subsystems draining Planinsko Polje. For each subsystem a hydraulic model comprising the main features of the inferred conduit network and inputs was made. The models were adjusted until their response to the typical flood situations gave a good qualitative fit to the response of the observation network. The results provide new insights into the mechanism of flood propagation through the system and its relation to the known conduit geometry. The hydraulic role of known cave passages is assessed and new flow pathways are proposed. Back-flooding within the aquifer causes an increase of head in the polje, followed by the activation of higher located ponor zones and flow pathways related to them. Hydrographs recorded in two caves located northwest from Planinsko Polje revealed pos sible high transmissivity zone of the Idrija Fault Zone and the mechanism of estavelles located at the polje’s north-western border. The approach taken in this work offers new insights into the relation between the conduit network geometry and flood mechanism. It can be used elsewhere in conduit-dominated systems with multiple accesses to groundwater flow and well constrained recharge.Key words: karst aquifer, epiphreatic zone, groundwater monitoring, hydraulic models, Planinsko Polje, Ljubljanica River.Dinamika podzemne vode med Planinskim poljem in izviri Ljubljanice, Slovenija Jame v epifraticni coni obicajno predstavljajo edini dostop do podzemne vode znotraj kraskega vodonosnika. Sodobni merilniki omogocajo kakovostne zvezne meritve razlicnih parametrov tudi v taksnih jamah. Merilna mreža z vec lokacijami znotraj izbranega vodonosnika lahko ponudi nove podatke o casovni in prostorski dinamiki toka podzemne vode. Taksna merilna mreža, z meritvami visine, temperature in elektroprevodnosti vode, je bila vzpostavljena v vseh pomembnejsih ponorih in vodnih jamah na obmocju med Planinskim poljem in izviri Ljubljanice. Do tri in pol leta dolgi nizi podatkov so bili analizirani z vidika razpoložljivih geoloskih, speleoloskih, meteoroloskih in hidroloskih podatkov ter osnovnih hidravlicnih nacel o epifreaticnem toku vode. Rezultat interpretacij so poenostavljeni modeli z domnevno razporeditvijo podzemnih kanalov v treh glavnih podsistemih, ki odvajajo Planisko polje. Za vsak podsistem je bil napravljen hidravlicen model z dotokom in mrežo kanalov, ki najbolje ponazarja resnicno stanje. Tekom raziskave so se hidravlicni modeli nadgrajevali do taksne mere, da je simulacija vodnega toka zadovoljivo ponazarjala dogajanje, izmerjeno v resnicnem okolju. Rezultati so prinesli nove ugotovitve o sirjenju in dinamiki poplavljanja skozi sistem ter njihovo povezavo s poznano geometrijo proucevanega vodonosnika. Ocenjena je bila hidravlicna vloga poznanih jamskih rovov, na podlagi njih pa interpretirane nove smeri pretakanja vode. Ugotovljeno je bilo tudi zajezitveno poplavljanje znotraj vodonosnika, ki vpliva tudi na vodostaj na polju in nadalje na aktivacijo visje ležecih požiralnikov ter njim sledecih kanalov. V dveh jamah severozahodno od Planinskega polja so visinski hidrogrami nakazali na obstoj bolj prepustnega obmocja Idrijske prelomne cone ter delovanje estavel na severozahodnem obrobju polja. Postopek, ki je bil uporabljen v pricujocem delu, omogoca nova dognanja o razporeditvi podzemnih kanalov in s tem povezano dinamiko poplavljanja v kraskem vodonosniku. Predstavljeno metodo je mogoce uporabiti tudi v drugih kraskih sistemih z dobro razvitimi kanali, z vec dostopi do toka podzemne toka vode in dobro poznanem dotoku v sistem.Kljucne besede: kraski vodonosnik, epifreaticna cona, spremljanje podzemne vode, hidravlicni modeli, Planinsko polje, Ljubljanica.

Vadose zone hydraulic properties impact the performance of surface-spreading MAR systems by controlling the rate of flow of water from land surface to the water table. Single- or double-ring or basin (pilot) infiltration tests are typically performed to estimate infiltration rates. Vadose zone hydraulic properties obtained from infiltration tests at land surface may differ greatly from those at depth, especially where the vadose zone is very thick. Evaluation of vadose zone properties is complicated by the zone being two phase (air and water), as opposed to the single-phase system of the phreatic zone. Vadose zone testing programs needs to consider the spatial variability in properties and the volume and area of investigation of tests relative to aquifer heterogeneity. Where project budgets and time are limited, the use of safety factors in design can compensate for uncertainty.

Asymmetric, pendant cements are considered good indicators for early lithification in the vadose zone. In the present study, asymmetric cements are recorded in thin-sections of a Lower Jurassic limestone from the Traras Mountains (northwest Algeria). Geopetal fabrics, however, indicate that these seemingly “pendant cements” are, in some places, oriented upwards, i.e., they have grown in the opposite direction from that expected, or they grew from grains towards the pore centers. These observations disprove their origin as gravitational cements precipitated from pendant water droplets on the undersides of grains as in the vadose zone. In contrast, a formation in the marine phreatic zone seems more probable. Under high-energy conditions, and after an early lithification stage with isopachous cements in the subtidal zone, strong tidally driven horizontal pore-water flow allowed sufficient seawater to pass through the slightly cemented but still highly permeable rock. Those grain sides, which were oriented towards the pore center, where faster flowing water prevailed, were more exposed to CaCO3-supersaturated percolating seawater and therefore the cements precipitated here show their greatest thickness. In relatively more protected areas around the margins of the pores, asymmetric cements are rarely developed. The resulting rock exhibits an unusual, heterogeneous cementation with preferential centripetal nucleation areas.

The present paper deals with a field experiments on evaporite rock samples and groundwater investigations in the Quinis test site, a hamlet of the Enemonzo municipality in NE Italy, were sinkholes occurred in the past and are still occurring causing severe damage to the existing infrastructures. The area is characterised by a Carnian evaporitic bedrock made of gypsum and anhydrite mantled by alluvial and colluvial deposits. In order to evaluate the loss of weight and volume of the subcropping evaporites as responsible for sinkholes, a field-experiment was carried out. Inside seven piezometers, at different depths, evaporitic rock samples were exposed to the naturally occurring variable climatic conditions such as degree of humidity, different air flow and hydrodynamic. The rock samples were installed at the beginning of April 2017 in the dry sections of piezometric tubes, in the vadose zone and in the phreatic zone. Data related to water level fluctuations were recorded by using data-logger devices and highlight significant changes in the water table. After 13 months of data recording (May 2018), rock samples were removed, reweighted and the volume loss measured. In addition, water from piezometer-experiment, representative of the groundwater circulation, were collected at different depths. The obtained results indicate that rock sample reduction is dependent on the hydrological regime and water chemistry and not on the number of days during which the samples remained submersed. In particular, the water geochemistry highlights the possible role in gypsum/anhydrite dissolution due to NaCl water admixing in a complex scenario. In additional, the geochemical data highlight the occurrence of some potentially toxic elements (As, Fe, Mn) at concentrations of concern in some water. This approach represents a novel contribution in the study of karst hazard in evaporites adding a tile to the knowledge of the fast evolutionary processes which cause sinkhole formation.

The process of zones formation in the layer was investigated. A new research method was developed for the saturation zone in the layer by discharge of sintering bowls with the structure conservation. Sintering mixture was pelletized using of melt paraffin instead of water. The destruction of the granules in areas with a dry charge material above the zone of saturation forms a zone of fine fractions with a height of about 6 mm with low gas permeability. Zone of fines increases the pressure loss in 1.4 times and the shrinkage of the layer – by 20–25 mm. Fines form a channel course of the gases in the zone of saturation clogging the channels with a diameter less than 0.6 mm. Negative impact on the permeability of the destruction layer of the pellets in the drying zone – intensive heating zone – and the saturation zone should be reduced to improve the efficiency of the sintering process.

Groundwater is the main need of society in everyday life. Groundwater is one of renewable resources but it doesn’t mean that it can be exploitated without limit. Several factors that affect the availability of groundwater derived from nature such as geological conditions, rainfall, and green areas should be considered. Water in the soil is stored in a porous layer and has a good permeability is called an aquifer. Cisarua area is located in West Bandung regency, West Java which is a hilly area that has a topography with a slope ranging from normal to steep. The land use in this area is still dominated with plantation and forest as green area. Groundwater aquifer characteristics in that area needs to be examined and analysed for the needs of the community and agricultural business. In this research, the writer used inversion modeling technique of geoelectric data to visualize the condition of subsurface. Resistivity inversion modelling of apparent resistivity data as a result of resistivity method with Wenner-Schlumberger configuration is then carried out with least-square method. The initial model is modified in an iterative manner such that the sum of square error of the difference between the model response and the observed data values is minimized. The result of resistivity modelling is used for analysis of aquifer characteristic such as lithology, depth and structure along with considering geological reference. As the result of modelling, the area of measurement is divided into three zones which are Zone of aeration, Zone of Saturation, and endapan formasi. Zone of aeration is located at depth 0-25 m with resistivity 20-100 Ohm.m and the predicted lithology is gravel or weathered soil. Zone of Saturation (akuifer) is located at depth 25-60 m with resistivity 4-30 Ohm.m and the predicted lithology is sandstone or clay. Endapan Formasi Cibereum is located at more than 60 m from ground with resistivity more than 100 Ohm.m and the predicted lithology is sandy tuff or dry breccia.

Multi-directional fluid flow and transport dynamics as intrinsic characteristics of hillslope flow regimes can strongly contribute to the quality evolution of groundwater resources and compartmentalization of subsurface ecosystems. However, their extent and importance in topographic highs (groundwater recharge areas) is typically less investigated, because productive groundwater bodies and thus monitoring activities are frequently lacking. In the Hainich Critical Zone Exploratory, we explored the hydrogeological functioning of the widely distributed setting of thin-bedded, alternating mixed carbonate-/siliciclastic bedrock, by using basic environmental timeseries. Up to 8-year records of weather parameters, ground temperatures, multi-depth hydraulic heads, and non-conservative tracers, were exploited applying a scheme for the exploratory analysis of dis-/continuous groundwater quality data. We identified transient, multi-directional flow dynamics, comprising fluctuating perched groundwater, localized recharge and groundwater mounding in the aeration zone that modify and partly reverse flow patterns in the phreatic zone. This interplay of flow dynamics within the hillslope aeration and phreatic zone causes significant re-distribution (e.g. oxygen, nitrate) that even overcome the “protective cover” of thick argillaceous strata by supplying surface-sourced substances to deep groundwater resources. As a factor for ecosystem compartmentalization, our results further suggest to carefully consider the hillslope multi-directional flow and matter exchange in biogeochemical models, as well as in resource protection and groundwater management practices.

Climate change may harm the growth and yield of sugarcane (Saccharum officinarum L.) without the introduction of appropriate irrigation facilities. Therefore, new irrigation methods should be developed to maximize water use efficiency and reduce operational costs. OPSIS (optimized subsurface irrigation system) is a new solar-powered automatic subsurface irrigation system that creates a phreatic zone below crop roots and relies on capillarity to supply water to the root zone. It is designed for upland crops such as sugarcane. We investigated the performance of OPSIS for irrigating sugarcane and evaluated its performance against sprinkler irrigation under subtropical conditions. We conducted field experiments in Okinawa, Japan, over the period from 2013 to 2016 and took measurements during spring- and summer-planted main crops and two ratoon crops of the spring-planted crop. Compared with sprinkler irrigation, OPSIS produced a significantly higher fresh cane yield, consumed less irrigation water and provided a higher irrigation water use efficiency. We conclude that OPSIS could be adopted as a sustainable solution to sugarcane irrigation in Okinawa and similar environments.

This paper monitor the deposition of Citrobacter in high porous medium in saline environment, the study investigate the behaviour of the contaminant in saline environment, the application of deterministic model developed simulation values that express the behaviour and effect from high porous medium, such shallow phreatic bed were observed to experiences fluctuation in soil porosity thus reflecting on the rate of concentration. The simulation developed locations that the concentration generated fluctuation to the depth were it was in significant in the formation, this was observed to be in an area were Citrobacter experiences degradation due to lack of microelement for growth. Moreso its deposition in shallow Phreatic zone has evaluated the rate of transport with respect to time and depth from the study carried out, it was observed to be predominantly influenced by high porosity in the formation, the influences of alluvium deposit in these condition could not influences the aquiferous zone by uniformity of the Phreatic deposited strata. Formation characteristics stated above were found significant in the migration of Citrobacter from surface to phreatic zone. The models were simulated and it produced theoretical values compared with other measured results, both parameters developed a favuorable fits validating the model.

The concept model of ancient buried hill karst reservoirs was built taking the NWKK carbonate rock oilfield in the South Turgay Basin in Kazakhstan as an example, and the characteristics of karst reservoirs and their controls on productivity were analyzed in vertical and horizontal directions. Vertically, the karst reservoirs can be subdivided into, from top to bottom, weathering crust zone, epikarst zone, caves zone, vadose zone and phreatic zone, in which the development of fractures is strengthened gradually; Six reservoir types, breccia pore, cave, vug, fracture-vug, fracture-pore and pore, were developed; Each karst zone has high oil production and low water cut in the initial stage because of the developed fractures and karst caves, but the production declines rapidly and the water cut rises fast. Horizontally, the karst reservoir characteristics are controlled by structure altitude and ancient lithofacies: the ancient buried hill with high structure altitude and loose lithology suffers from stronger weathering and leaching, has much more solution caves and holes, the main reservoir types are breccia pore, cave, and vug, while the ancient buried hill with low structure altitude and compacted lithology has highly developed fractures and stronger communication with bottom water, the main reservoir types are fracture-vug and fracture-pore, and the reservoirs have better productivity effect but rapid production declines and water cut rising. Different areas in plane should adopt different development techniques and policies. Key words: ancient buried hill, karst reservoir, reservoir characteristics, reservoir concept model, productivity characteristics, South Turgay Basin

Switching crop type and consequently changing irrigation and fertilization regimes lead to alterations in deep percolation and solute concentrations of pore water. Herein, observations from the deep vadose zone and model simulations demonstrate the changes in water, chloride, and nitrate fluxes under a commercial greenhouse following the change from tomato to lettuce cropping. The site, located above a phreatic aquifer, was monitored for 5 years. A vadose-zone monitoring system was implemented under the greenhouse and provided continuous data on both temporal variations in water content and chemical composition of the pore water at multiple depths in the deep vadose zone (up to 20 m). Following crop switching, a significant reduction in chloride concentration and dramatic increase in nitrate were observed across the unsaturated zone. The changes in chemical composition of the vadose-zone pore water appeared as sequential breakthroughs across the unsaturated zone, initiating at land surface and propagating down toward the water table. Today, 3 years after switching the crops, penetration of the impact exceeds 10 m depth. Variations in the isotopic composition of nitrate (18O and 15N) in water samples obtained from the entire vadose zone clearly support a fast leaching process and mobilization of solutes across the unsaturated zone following the change in crop type. Water flow and chloride transport models were calibrated to observations acquired during an enhanced infiltration experiment. Forward simulation runs were performed with the calibrated models, constrained to tomato and lettuce cultivation regimes as surface boundary conditions. Predicted chloride and nitrate concentrations were in agreement with the observed concentrations. The simulated water drainage and nitrogen leaching implied that the observed changes are an outcome of recommended agricultural management practices.

Summary Even though karstic aquifers are important freshwater resources and frequently occur in mountainous areas, recharge processes related to snowmelt have received little attention thus far. Given the context of climate change, where alterations to seasonal snow patterns are anticipated, and the often-strong coupling between recharge and discharge in karst aquifers, this research area is of great importance. Therefore, we investigated how snowmelt water transits through the vadose and phreatic zone of a karst aquifer. This was accomplished by evaluating the relationships between meteorological data, soil–water content, vadose zone flow in a cave 53 m below ground and aquifer discharge. Time series data indicate that the quantity and duration of meltwater input at the soil surface influences flow and storage within the soil and epikarst. Prolonged periods of snowmelt promote perched storage in surficial soils and encourage surficial, lateral flow to preferential flow paths. Thus, in karstic watersheds overlain by crystalline loess, a typical pedologic and lithologic pairing in central Europe and parts of North America, soils can serve as the dominant mechanism impeding infiltration and promoting shallow lateral flow. Further, hydrograph analysis of vadose zone flow and aquifer discharge, suggests that storage associated with shallow soils is the dominant source of discharge at time scales of up to several weeks after melt events, while phreatic storage becomes import during prolonged periods without input. Soils can moderate karst aquifer dynamics and play a more governing role on karst aquifer storage and discharge than previously credited. Overall, this signifies that a fundamental understanding of soil structure and distribution is critical when assessing recharge to karstic aquifers, particularly in cold regions.

Summary Above a shallow unconfined aquifer, a considerable amount of water is stored in the vadose zone. Through water exchange with the underlying unconfined aquifer, the vadose zone affects the groundwater table dynamics and overall behavior of the aquifer. In this paper, we examine tide-induced groundwater table fluctuations in unconfined aquifers influenced by vadose zone of finite thickness. Under the condition of small aquifer thickness ( D ) compared with the groundwater wavelength ( L ) (i.e., μ 2 = D / L 2 ≪ 1 ) and small boundary oscillation amplitude ( a ) (i.e., e = a / D ≪ 1 ) (where μ 2 and e are two parameters), an approximate analytical solution was derived to quantify systematically the vadose zone effects, with a particular consideration of capping by the ground surface, i.e., the upper boundary of the vadose zone. Depending on the extent to which the capillary rise is truncated by the ground surface, the vadose zone enhances the groundwater table fluctuations in an unconfined aquifer. However, the mean groundwater table height and exchange between surface water and groundwater are reduced due to the presence of the vadose zone. These effects are intensified with increased capillary rise, but weakened as the vadose zone thickens. This study provides a criterion for assessing the importance of vadose zone in modulating the response of unconfined aquifers to low-frequency forcing oscillations such as tides.

We characterize the fracture pattern, including both meso-scale joints and macro-scale faults, within the central sector of Sierra de las Nieves (Betic Cordillera, S Spain), which contains one of the largest karstification systems in Europe. Structural data were compared with the direction pattern of the karstic conduit network of the largest caves. Carbonate rocks were deformed in a collisional setting and exposed at the surface since the early Miocene. Normal and normal–oblique faults trending NW–SE to WNW–ESE are the most prominent brittle structures, having formed coevally with shorter NE–SW normal to normal–dextral after the main thrusting phase. In addition, two main open joint sets striking NW–SE and NE–SW developed on a broad scale. Orthogonal normal faults and open joints suggest an extensional setting characterized by horizontal minimum (S3) and intermediate (S2) stress axes of similar magnitudes that intermittently shifted their positions during the middle-to-late Miocene. Vertical water flow coming from direct recharge sectors tends to infiltrate across these high-dipping faults, mainly concentrating at fault intersections, thus favoring sub-vertical conduit formation within the vadose zone. Horizontal paleo-phreatic levels are perched linked to the recent uplift undergone by the sector, giving us the opportunity to analyze the incidence of fractures at the phreatic zone. Joint sets determine the hydraulic anisotropy within the former phreatic levels. Because our study illustrates the primary role of diverse tectonic structures during massive multiphase cave development above and below the water table, it could contribute to better constraining of the models of karstic conduit formation.

Tectonic research and morphological observations were carried out in six caves (Kalacka, Goryczkowa, Kasprowa Nizna, Kasprowa Średnia, Kasprowa Wyznia and Magurska) in the Bystra Valley, in the Tatra Mountains. There are three cave levels, with the youngest active and the other two inactive, reflecting development partly under epiphreatic and partly under phreatic conditions. These studies demonstrate strong control of the cave pattern by tectonic features, including faults and related fractures that originated or were rejuvenated during uplift, lasting from the Late Miocene. In a few local cases, the cave passages are guided by the combined influence of bedding, joints and fractures in the hinge zone of a chevron anticline. That these cave passages are guided by tectonic structures, irrespective of lithological differences, indicates that these proto-conduits were formed by “tectonic inception”. Differences in the cave pattern between the phreatic and epiphreatic zones at a given cave level may be a result of massif relaxation. Below the bottom of the valley, the effect of stress on the rock mass is related to the regional stress field and only individual faults extend below the bottom of the valley. Thus in the phreatic zone, the flow is focused and a single conduit becomes enlarged. The local extension is more intense in the epiphreatic zone above the valley floor and more fractures have been sufficiently extended to allow water to flow. The water migrates along a network of fissures and a maze could be forming. Neotectonic displacements (of up to 15 cm), which are more recent than the passages, were also identified in the caves. Neotectonic activity is no longer believed to have as great an impact on cave morphology as previously was thought. Those faults with displacements of several metres, described as younger than the cave by other authors, should be reclassified as older faults, the surfaces of which have been exposed by speleogenesis. The possible presence of neotectonic faults with greater displacements is not excluded, but they would have had a much greater morphological impact than the observed features suggest.

The Ogallala-High Plains aquifer is an important resource for irrigated agriculture in a semi-arid region of the United States. Steep declines in groundwater levels are putting increasing strain on the viability of the aquifer for irrigation, necessitating improved estimates of recharge rates and sources to the aquifer. This study uses a combined approach to obtain high resolution geochemical and isotopic composition of the vadose zone and aquifer pore fluids to better understand recharge dynamics to the aquifer. Significant differences between the shallow, intermediate and deep vadose zone and shallow and deep aquifer indicate modern precipitation is not providing a significant source of recharge to the aquifer across a large area (diffuse recharge). Rather, recharge to the aquifer is a result of either focused recharge or long-term, delayed drainage from the portion of the vadose zone which was saturated before irrigation development.

The "HYDRUS package for MODFLOW" is an existing MODFLOW package that allows MODFLOW to simultaneously evaluate transient water flow in both unsaturated and saturated zones. The package is based on incorporating parts of the HYDRUS-1D model (to simulate unsaturated water flow in the vadose zone) into MODFLOW (to simulate saturated groundwater flow). The coupled model is effective in addressing spatially variable saturated-unsaturated hydrological processes at the regional scale. However, one of the major limitations of this coupled model is that it does not have the capability to simulate solute transport along with water flow and therefore, the model cannot be employed for evaluating groundwater contamination. In this work, a modified unsaturated flow and transport package (modified HYDRUS package for MODFLOW and MT3DMS) has been developed and linked to the three-dimensional (3D) groundwater flow model MODFLOW and the 3D groundwater solute transport model MT3DMS. The new package can simulate, in addition to water flow in the vadose zone, also solute transport involving many biogeochemical processes and reactions, including first-order degradation, volatilization, linear or nonlinear sorption, one-site kinetic sorption, two-site sorption, and two-kinetic sites sorption. Due to complex interactions at the groundwater table, certain modifications of the pressure head (compared to the original coupling) and solute concentration profiles were incorporated into the modified HYDRUS package. The performance of the newly developed model is evaluated using HYDRUS (2D/3D), and the results indicate that the new model is effective in simulating the movement of water and contaminants in the saturated-unsaturated flow domains.

Hydrochemical solute concentrations in the shallow subsurface can be spatially highly variable within small scales, particularly at interfaces. However, most monitoring systems fail to capture these small scale variations. Within this study, we developed a high resolution multilevel well (HR-MLW) with which we monitored water across the interface of the unsaturated and saturated zone with a vertical resolution of 0.05-0.5 m. We installed three of these 4 m deep HR-MLWs in the riparian zone of a third-order river and analyzed for hydrochemical parameters and stable water isotopes. The results showed three distinct vertical zones (unsaturated zone, upper saturated zone, lower saturated zone) within the alluvial aquifer. A 2 m thick layer influenced by river water (upper saturated zone) was not captured by existing monitoring wells with higher screen length. Hydrochemical data (isotopes, total ions) were consistent in all HR-MLWs and showed similar variation over time emphasizing the reliability of the installed monitoring system. Further, the depths zones were also reflected in the NO

Little is known about how trace metals accumulate and cycle in conduits within the phreatic zone. These water-filled conduits can receive floodwater that allows metals to accumulate, similar to air-filled caves, but are more susceptible to reducing conditions following floods because oxygen is limited to dissolved concentrations. If sufficient reactive organic carbon is transported into the aquifer, oxygen consumption will lower Eh and mobilize manganese and iron. To evaluate this accumulation and mobilization of metals, we analyzed the geochemical and isotopic composition of water, solid metal oxide, and limestone samples from two phreatic systems in north-central Florida where river water displaces aquifer water following storms. River water was a net source of trace metals to the aquifer; however, manganese depletion in the interior of the metal oxides relative to concentrations in intruding river water indicates not all metals are retained in the aquifer as redox conditions changed. The metal oxides are actively incorporating metals from floods, with anthropogenically sourced lead from surface water on the outer portion of the metal oxide.

International audience; The concept of superficial structure relates to surficial deformations that are determined neither by tectonic deformation nor by surface geomorphic processes sensu stricto. This work addresses two mechanisms leading to structural surface disturbances in the Lutetian strata of the Eocene plateaux of the eastern Paris Basin. Firstly, mechanical release which is associated with stress-relief during Quaternary valley downcutting. It results in lateral spreading of the middle Lutetian limestone, and subsequent sub-erosion of underlying sands may cause valley-side cambering. Secondly, ghost-rock karstification in the phreatic zone which is leading to surficial collapse of the upper Lutetian cover. Geological structure (thickness and porosity of the middle Lutetian limestone) and valley-side slopes stratigraphy (position of the upper Ypresian sand) control the spatial distribution of these processes. Ghost-rock karstification, conditioned by tectonic joints is confined to the west; to the east, cambering processes occur where upper Ypresian sand aquifer and alluvial aquifer are connected. During the Quaternary, periglacial conditions account for cambering processes and also for a second phase of karstification within an aquifer perched in the active layer, and from mechanical release joints. Resultant morphological features are then inherited and cambering is even a fossil process where upper Ypresian sand crops out above the valley floor. Consequently, large-scale landforms, derived from the superficial structure, are essentially inactive.

In this paper, numerical simulations of regional-scale groundwater flow of North Bengal Plain have been carried out with special emphasis on the arsenic (As)-rich alluvium filled gap between the Rajmahal hills on the west and the Garo hills on the east. The proposed concern of this modelling arose from development that has led to large water table declines in the urban area of English Bazar block, Malda district, West Bengal and possible transport of As in the near future from the adjacent As-polluted aquifer. Groundwater occurs under unconfined condition in a thick zone of saturation within the Quaternary alluvial sediments. Modelling indicates that current pumping has significantly changed the groundwater flowpaths from pre-development condition. At the present pumping rate, the pumping wells of the urban area may remain uncontaminated till the next 25 yrs, considering only pure advection of water but some water from the As-polluted zone may enter wells by 50 yrs. But geochemical and other processes such as adsorption, precipitation, redox reaction and microbial activity may significantly retard the predicted rate by advective transport. In the rural areas, majority of the water pumped from the aquifer is for irrigation, which is continuously re-applied on the surface. The near-vertical nature of the flowpaths indicates that, where As is present or released at shallow depths, it will continue to occur in pumping wells. Modelling also indicates that placing all the pumping wells at depths below 100 m may not provide As-free water permanently.

Anaerobic ammonium oxidation (anammox) is recognized as an important process for nitrogen cycling, yet little is known about its role in the subsurface biosphere. In this study, we investigated the presence, abundance, and role of anammox bacteria in upland soil cores from Tianjin, China (20 m depth) and Basel, Switzerland (10 m depth), using isotope-tracing techniques, (q)PCR assays, and 16 S rRNA & hzsB gene clone libraries, along with nutrient profiles of soil core samples. Anammox in the phreatic (water-saturated) zone contributed to 37.5–67.6% of the N-loss (up to 0.675 gN m−2d−1), with anammox activities of 0.005–0.74 nmolN g−1soil h−1, which were even higher than the denitrification rates. By contrast, no significant anammox was measured in the vadose zone. Higher anammox bacterial cell densities were observed (0.75–1.4 × 107copies g−1soil) in the phreatic zone, where ammonia-oxidizing bacteria (AOB) maybe the major source of nitrite for anammox bacteria. The anammox bacterial cells in soils of the vadose zone were all 3copies g−1soil. We suggest that the subsurface provides a favorable niche for anammox bacteria whose contribution to N cycling and groundwater nitrate removal seems considerably larger than previously known.

The Frasassi caves present a unique opportunity to study sulfuric acid speleogenesis in a large karst system that contains active sulfidic processes as well as relict features produced by past speleogenetic episodes. The caves consist of a network of ramifying, mainly subhorizontal passages that reach more than 30 km in total length, and are organized in superimposed and interconnected levels. Sulfidic groundwaters are accessible in the lowermost levels. The water chemistry in the shallow phreatic zone is influenced by mixing phenomena between the sulfidic groundwaters and descending oxygenated water and, to some extent, gas exchange with the cave atmosphere. The sulfidic waters are corrosive with respect to limestone, with average limestone dissolution rates around 100 mm 10−3 year−1 for submerged tablets. The release of gases to the air also causes wall corrosion (linear corrosion rate up to 85 mm 10−3 year−1), which produces gypsum replacement crusts above the water table. Morphological and isotopic analyses show that large relict gypsum deposits in the upper dry levels were created by the same mechanism. Sulfide-oxidizing chemosynthetic bacteria living in the cave produce organic matter and support a rich and diverse ecosystem in the sulfidic branches, and these microorganisms contribute to sulfur cycling and cave formation processes. The evolution of the older cave levels during the Pleistocene was a complex result of changing regional geomorphological and hydrogeological regimes as well as local factors that affect water movement and gas exchange in the shallow phreatic zone within the cave.