Hydrochemical Information Research Articles

Assessing the groundwater quality of El Fahs aquifer (NE Tunisia) using multivariate statistical techniques and geostatistical modeling

This study is the first attempt to characterize the quality status of El Fahs aquifer by combining graphical tools, multivariate statistical techniques and traditional geostatistical methods. Water samples are collected from thirty-six observation wells during April 2016 to characterize the physicochemical properties of the aquifer. Subsequently, these samples are partitioned into three hydrochemically distinct water classes (i.e., C1, C2, and C3) using the K-means clustering method. Principal Component Analysis is used to reduce the dimensionality of the dataset prior performing the clustering computations, resulting in clusters of higher quality than the non-reduced case in terms of Silhouette coefficient. Piper diagram is used to display the chemical composition of the samples, revealing the dominant role of Mg–Ca–Cl water type for all three classes, whereas Sodium and Sulfate were found to be the second most important cations and anions respectively. Indicator kriging (IK) is used to identify the probability of occurrence of the hydrochemical classes beyond the sampling locations. It is found that Class 1, associated with fresh groundwater component, is most probable to occur at the central part of the plain, mainly due to the presence of a dense hydrological network, whereas Classes 2 (agricultural activities) and 3 (dissolution of evaporate geological formations) are expected to occur at the southern and northern regions respectively. IK also identified the regions associated with high levels of uncertainty, mostly occurring in a large portion of the northern area due to the absence of available hydrochemical information. The results showed that integration of graphical methods, multivariate statistical techniques and geostatistical modeling, is an efficient approach for characterizing the hydrochemical status of the aquifer system, to spatially optimize the groundwater monitoring well networks and quantify the uncertainty levels of the water classes in a systematic way.

Combining multi-isotope technology, hydrochemical information, and MixSIAR model to identify and quantify nitrate sources of groundwater and surface water in a multi-land use region.

Accurate identification of nitrate(NO3-) sources is the premise of non-point source pollution control in watersheds. The multiple isotope techniques (δ15N-NO3-, δ18O-NO3-, δ2H-H2O, δ18O-H2O), combined with hydrochemistry characteristics, land use information, and Bayesian stable isotope mixing model (MixSIAR), were used to identify the sources and contributions of NO3- in the agricultural watershed of the upper Zihe River, China. A total of 43 groundwater (GW) and 7 surface water (SFW) samples were collected. The results showed that NO3- concentrations of 30.23% GW samples exceeded the WHO maximum permissible limit level, whereas SFW samples did not exceed the standard. The NO3- content of GW varied significantly among different land uses. The averaged GW NO3- content in livestock farms (LF) was the highest, followed by vegetable plots (VP), kiwifruit orchards (KF), croplands (CL), and woodlands (WL). Nitrification was the main transformation process of nitrogen, while denitrification was not significant. Hydrochemical analysis results combined with NO isotopes biplot showed that manure and sewage (M&S), NH4+ fertilizers (NHF), and soil organic nitrogen (SON) were the mixed sources of NO3-. The MixSIAR model summarized that M&S was the main NO3- contributor for the entire watershed, SFW, and GW. For contribution rates of sources in GW of different land use patterns, the main contributor in KF was M&S (contributing 59.00% on average), while M&S (46.70%) and SON (33.50%) contributed significantly to NO3- in CL. Combined with the traceability results and the situation that land use patterns are changing from CL to KF in this area, improving fertilization patterns and increasing manure use efficiency are necessary to reduce NO3- input. These research results will serve as a theoretical foundation for controlling NO3- pollution in the watershed and adjusting agricultural planting structures.

ОЦЕНКА СОСТОЯНИЯ ВОДНЫХ ЭКОСИСТЕМ ПО ИНТЕГРАЛЬНЫМ ГИДРОХИМИЧЕСКИМ ПОКАЗАТЕЛЯМ В ГОСУДАРСТВЕННОМ МОНИТОРИНГЕ СОСТОЯНИЯ И ЗАГРЯЗНЕНИЯ ОКРУЖАЮЩЕЙ СРЕДЫ

The paper presents some methodological approaches to the development of the aquatic ecosystems state classifier according to integral hydrochemical indicators. The classifier has been developed based on the analysis of the Roshydromet long-term routine hydrochemical information for a large number of rivers and their reaches located in various natural and climatic zones of Russia. Criteria for assessing the state of aquatic ecosystems have been established taking into account water salinity: from natural, equilibrium, and stressful to critical or catastrophic. Testing of the methodological approaches and verification of the state assessment results was carried out by the example of individual river ecosystems in the European part of Russia. The majority of ecologically safe river ecosystems functioning in their natural state have been shown to belong to waters with low salinity and to be located in northern regions. In the center and the south of the European part of Russia, river ecosystems in equilibrium, stressful, or critical state dominate.

The Hydraulic Connection Analysis of Dongying Geothermal Fluid Using Hydrochemical Information and Isotope Data in Tianjin Coastal Regions

Dongying’s Paleogene geothermal resources are an important part of the geothermal resources of the Tianjin coastal region. The extent of the geothermal fluid resources and the supply relationship have become increasingly important, and will determine whether demand targets can be met. Dongying’s Paleogene formation in the Tianjin coastal regions is widely distributed to the east of the Cangdong fracture, but it is absent west of the Cangdong fracture. On the basis of introducing the geological characteristics and depositional characteristics of the Dongying formation, we analyzed the hydraulic conductivity of the Cangdong fracture to the Dongying formation geothermal reservoir from the aspects of geological condition, dynamic of groundwater level and hydrologic geochemistry. Based on the hydrochemical information and the isotope data gained during the water quality evaluation and isotope data analysis process, we discovered the main chemical composition, hydrogen and oxygen isotope data and geothermal fluid age are significantly different between the Dongying formation geothermal reservoir and the overlying and underlying geothermal reservoirs. It is inferred that the hydraulic conductivity of the Cangdong fracture to the Dongying formation geothermal reservoir in this area is weak, and along the Haihe fracture, where the Haihe fracture intersects with the Cangdong fracture, there is a certain hydraulic conductivity. In addition, there is no obvious hydraulic connection between the Dongying formation and the upper and lower geothermal reservoirs.

Remediation of chlorinated aliphatic hydrocarbons (CAHs) contaminated site coupling groundwater recirculation well (IEG-GCW®) with a peripheral injection of soluble nutrient supplement (IEG-C-MIX) via multilevel-injection wells (IEG-MIW)

An innovative Groundwater Circulation Well (GCW) process was configured, installed, and tested for optimizing the distribution of a soluble nutrient supplement in a heterogeneous aquifer for reductive dehalogenation. This generated an in-situ bioreactor for the enhanced treatment of chlorinated aliphatic hydrocarbons (CAHs). At a site in Barcelona, Spain, trichloroethylene (TCE) concentration was found in the source area to a maximum value of up to 170 mg/L, while the degradation products like 1,2-dichloroethylene (1,2-DCE) and vinyl chloride (VC) were detected in significantly lower concentrations or were even absent. The novel system combined a vertical recirculation well (IEG-GCW®) and four multilevel injection wells (IEG-MIWs) to introduce the carbon solution into the aquifer. A 12 m deep IEG-GCW® equipped with 2 screened sections were located in the center of the 4 IEG-MIWs. The GCW induced flow moves the groundwater in an ellipsoidal recirculation cell to spread the supplements from the central GCW and from the peripheral MIWs in the aquifer body. Two multilevel sampling wells (IEG-MLSWs®) in the radius of influence (ROI) monitor the remediation process to capture hydrochemical variations along the vertical aquifer sections. A multi-source model harmonizes geological and hydrochemical information during different remediation stages, guiding the adaptation of the remediation strategy to physicochemical conditions and unmasking the decontamination mechanics induced by the remedial actions. Hydrochemical monitoring of MLWS and the stable carbon isotopic signature of cis-1,2-DCE and VC show the mobilization of secondary contamination sources triggered by recirculation during remediation, the stimulation of microbiological activity following nutrient supplement via GCW and MIWs, and the strong decrease of CAHs concentrations at different aquifer levels. Evidence from the first application at the field scale reveals a significant increase in the chloroethane biodegradation rate and short-term effectiveness of the innovative remediation strategy. GCW-MIWs synergy represents a promising strategy to degrade CAHs in a shorter period through the combination of a controllable hydraulic system, effective nutrient distribution, and the monitoring of the remediation process.

Assessment of the depth of the upper boundary of the hydrogen sulphide zone of the black sea with the buoys' data of 2015-2022

Biocenoses of the Black Sea are ones of the most vulnerable natural systems of the Earth. About 87 % of the Black Sea water volume is occupied by the hydrogen sulfide zone. Ecosystems of the thin layer of the upper oxygen zone are extremely sensitive to both anthropogenic impact and the influence of natural factors, the intensification of which has been observed recently due to rapid global climate change. The aim of the work is to assess the depth appearance, spatial distribution and change of the upper boundaries of the hydrogen sulfide zone of the Black Sea with the buoys ARGO data. In the article it was used hydrophysical and hydrochemical information obtained from the oceanographic database of the ARGO project in the Black Sea for the period from March 2015 to March 2022, such as: temperature, salinity, dissolve oxygen and hydrogen sulfide. A total of 591 arrays were analysed. A critical analysis of the quality of the selected information was carried out. The profile data has been adjusted. When processing the material, the method of optimal interpolation, graphic and statistical analysis were used. The original programs of UkrSCES were used. It was concluded according to the results of the work that the upper boundary of the anaerobic zone of the Black Sea in areas of buoy drift was located at depths of 100-180 meters. The difference in the indications for determining the boundaries according to two independent criteria: the depth of the water bodies with a hydrogen sulfide concentration of 3 μmol/kg, and the depth of the iso-surface of the conditional density of 16.18, which on average fluctuated within ±7 meters. In some areas, significant fluctuations in the upper limit of the anaerobic zone, caused by the influence of local hydrodynamic vortices, or removal of intrusive water from the Bosphorus Strait, were noted. The spatiotemporal variability of the sub-oxygen zone in the areas of buoy-profilometer drift, as well as the areas where this layer has minimum and maximum power.

МНОГОЛЕТНЯЯ ИЗМЕНЧИВОСТЬ ИОННОГО СТОКА КРУПНЫХ РЕК АРКТИЧЕСКОЙ ЗОНЫ РОССИИ

Studies of river ion runoff and its temporal variability are important. It affects coastal waters and is interrelated with climatic changes in the Arctic region. Long-term data on the chemical runoff of macrocomponents (chlorides, sulfates, hydrocarbonates, calcium and magnesium ions) at the outlet sections of large Arctic rivers in Russia - Pechora, Usa, Yenisei, Ob, Pur, Taz, Lena, Yana and Kolyma are given. The values of volumes and modules of chemical runoff were calculated on the basis of long-term (1980-2018) hydrological and hydrochemical information from the state observation system of Roshydrom-et. It is shown that the change in the absolute values of the chemical runoff is consistent with the water inflow. Greatest contribution to the ionic runoff is made by hydrocarbonates. The intra-annual change in the water inflow and the macrocomponents runoff occurs synchronously. There is a decisive role of water runoff in the formation of chemical runoff from the catchments of large Arctic rivers. Comparison of the chemical runoff modulus indicator made it possible to classify them into low, medium or high ionic runoff rivers. It was found that the maximum runoff of macrocomponents occurs from the catchment of the Usa river. It is may be due to active processes of chemical denudation and climate change.

Subsurface hydrological processes and groundwater residence time in a coastal alluvium aquifer: Evidence from environmental tracers (δ18O, δ2H, CFCs, 3H) combined with hydrochemistry

As an important part of the water cycle, the hydrologic process and chemical compositions of groundwater have changed significantly due to the joint influence of climate change and human activities. Groundwater salinization becomes a serious threat to water security in coastal areas. In order to assess the relationships between surface water, groundwater and seawater in the coastal plain, we performed a synthesis study based on hydrochemical-isotopic data, hydro-dynamical records and environmental tracers. Deuterium and oxygen isotopes and water chemical indicators were used to identify pollution status, salt sources and migration processes. Radioactive isotopes and gaseous tracers were used to obtain reasonable groundwater age. With the help of multi-tracer approach, the surface-groundwater interaction, salinization of groundwater and nitrate pollution were identified in the Yang-Dai River plain, northern China. The estimated groundwater ages determined from chlorofluorocarbons (CFCs) and tritium (3H) ranges from 18 to 41 years in this area, suggesting a modern groundwater circulation. The spatial distribution of the groundwater age varies significantly due to horizontal hydrogeological heterogeneity. The total dissolved solids (TDS) content of the groundwater near the Well Field (average: 970 mg/L) was higher than the TDS values in samples derived from places located at an equivalent distance to the coastal line (average is 708 mg/L), which resulted from the vertical seawater intrusion through river channels and pollutant inputs from agriculture activities. The nitrate concentrations in groundwater were elevated up to 271 mg/L and increased with increasing groundwater age, which was another water environment problem that should be solved urgently but lacks sufficient attention for years. This study provides a conceptual model with a number of comparable hydrochemical information, which is significant for regional pollution control and water resources management.

Применение Веб-ГИС-технологий в задачах экомониторинга на примере загрязнений озер Мурманской области

When carrying out long-term environmental monitoring programs, a whole series of problems arise related to storage, processing, visualization of data obtained, their presentation in a form suitable for making managerial decisions and / or public perception. The received volume of primary information requires structured storage, a special multivariate analysis to identify long-term trends and assess dangers of possible negative phenomena, a different level of accessibility and generalization of results for various information consumers. At the same time, copyrights of the information owners must be respected. As a solution to these problems, it is proposed to use GIS-oriented information systems for storing and processing the accumulated information. The paper considers the main aspects of creating a GIS portal for publishing results of hydrochemical studies of water objects in the Murmansk region. A review of existing developments and approaches to solving this problem is given. A technique for creating a GIS portal based on open source software is proposed. Issue of implementing copyright protection mechanisms for owners of hydrochemical information considered partially. Currently, a pilot version of the GIS portal has been developed, which stores the web version of the map «Hydrochemical characteristics of the lakes of the Murmansk region». In the future, it is planned to supplement the resource with the blocks «Hydrology», «Bottom sediments of Murmansk region lakes», «Hydrobionts of Murmansk region lakes» and visualization tools for primary data. This work is carried out as part of a project to increase availability of environmental information for both the public and decision-makers. The project may also be of interest to scientific organizations. Keywords: hydrochemical information, GIS, QGIS, GIS portal.

Analysis of the total phosphorus runoff in the Neva River

The paper deals with the problems of water quality assessment taking into account the features of hydrochemical information. The analysis of dynamics of total phosphorus into the Neva River runoff from 1978 to 2017 is presented.

Sensitivity Assessment of a Runoff Formation Model in the Mozhaisk Reservoir River Basin

The physically based model of river runoff formation with a daily resolution ECOMAG was adapted for the Mozhaisk Reservoir with an area of 1360 km2. A large series of numerical experiments were carried out in order to investigate the sensitivity of the model to the spatial resolution of land surface characteristics and the size of calculation cells. Digital elevation models (DEMs) of three different spatial resolutions (50, 100 m, and 2 km) were used along with model schematizations of the catchment area and river network with varying detail. In addition, the model sensitivity to sets of calibration parameters when modelling genetic runoff components was studied, as a part of the approaches to mitigating the problem of equifinality. The importance of incorporating additional hydrochemical information for a correct description of the spatial and temporal genetic structure of river runoff is shown.

EU Nitrates Directive, from theory to practice: Environmental effectiveness and influence of regional governance on its performance

Despite the European Nitrate Directive (ND) being issued almost 30 years ago, groundwater nitrate contamination is still a serious threat to ecosystems and human health. In one of the areas most affected by nitrates, the Lombardy Plain (Italy), the effectiveness of the ND and the capacity of governance to support its application correctly was assessed using a socio-hydrogeological approach. Nitrate trends over 11 years show that most regions present steady or increasing concentrations, highlighting how contamination can affect previously impaired situations and supposedly resistant and resilient aquifers. Stakeholder network analysis reveals that the governance framework does not support knowledge dissemination and changes in farmers’ attitudes, hindering water quality improvements. Nitrogen input needs to be reduced and manure relocation monitored. The local governance scale has a key role in enhancing ND dissemination. Reports to the EU Commission should integrate multi- or interdisciplinary evaluation of trends, including governance dynamics, alongside hydrochemical information.

Rivers in the Russian Arctic support zones and their current status

Implementation of projects to create support zones is closely linked to the optimization of the system of state control over the environmental situation in the Russian Arctic. Previous studies have shown that zones of ecological disadvantage, as well as impact areas, have formed on these territories. In this regard, the urgency of developing and adapting scientific methods for monitoring the status and methods of regulating the quality of freshwater ecosystems is growing. Recent studies show that the reasons for changing the quality of freshwater ecosystems are the introduction of the substances with anthropogenic origin into the water mass and the modification of chemical components of the natural water environment, changes in its physical characteristics and other properties of the freshwater ecosystem.The aim of this work is to assess the hydrological and environmental state of the river ecosystems in the support zones of the Russian Arctic. The analysis of the long-term regime hydrochemical information (1990–2010) of the state observation network of the Roshydromet was carried out using methods of complex indicators calculating and risk of anthropogenic impact assessments.Variability of the water pollution degreeis analyzed. Priority and critical hydrochemical indicators are identified. It is shown that the role of the anthropogenic component is currently determinative in the transformation of their hydrochemical regime for the river ecosystems of the support zones under study. Their hydrochemical regime is characterized by high spatial, interannual and intra-annual variability of the component composition of the aquatic environment; formation of a higher “anthropogenically-altered natural background”; periodic accumulation in the water environment of priority pollutants to concentrations of tens of hundreds of times the maximum permissible concentrations, an increase in the frequency of cases of high and extreme high pollution.

Hydrological and hydrochemical behavior of a riparian zone in a high-order flatland stream.

Hydrological and hydrochemical processes occurring within riparian zones in temperate mid-latitudes flatland areas have significant implications for water management by controlling nutrient transfer between the watershed and the stream system. The riparian zone in a high-order flatland stream located within a 7063-km2 agricultural watershed in Argentina was investigated to study its hydrological connectivity to upland zones, interactions with the stream, and their implications for groundwater hydrochemistry. The analysis was based on 9-year-long time series of groundwater/stream water levels collected along a 220-m-long transect comprising six piezometers, a river stage sensor, and hydrochemical information from 37 groundwater/stream water sampling campaigns. Samples were analyzed for electrical conductivity (EC), Cl-, SO4+2, (Ca+2 + Mg+2), pH, and redox potential (ORP). Data were interpreted using descriptive statistics, statistical tests, groundwater flux calculations, and identification of hydrological patterns and associated hydrochemical responses. The system was hydrologically controlled by shallow groundwater. Three representative landscape hydrological patterns were identified: disconnected, incipient-weakly connected, and fully connected. Groundwater hydrochemistry was closely linked to hydrological connectivity, which played an important role in the mobilization and fluxes of solutes. Overall, groundwater EC, Cl-, SO4+2, and (Ca+2 + Mg+2) concentrations decreased from upland to lowland. For full connectivity, Cl- concentrations reduced 33%, while SO4+2 reduced 42%, demonstrating the system's buffering capacity. This investigation constitutes the first attempt to formulate the riparian zone functioning in this agricultural region and has contributed to the understanding on the complex interactions between hydrologic regimes of large flatland-high-order streams and shallow groundwater systems in fine-texture sediments.

Microbial Function and Hydrochemistry within a Stratified Anchialine Sinkhole: A Window into Coastal Aquifer Interactions

Anchialine sinkholes provide insight into coastal aquifer systems and coastal mixing processes. Aquifer microbial community function is usually inferred from hydrochemical information, but there are few direct studies of microbial communities in the Floridan Aquifer. Hospital Hole is a 43 m-deep stratified sinkhole under the Weeki Wachee River, FL, with three distinct brackish layers: a hypoxic layer, a chemocline and a sulfidic anoxic layer. Illumina sequencing and bioinformatic tools were used to reconstruct metabolic functions and interactions of microbial communities in each layer. Each layer appears to originate from different parts of the coastal mixing zone and has a distinct microbial community with unique functions, which are influenced by the respective hydrochemistry. Sulfide oxidation and nitrate reduction are the most abundant functions. Syntrophy between methane oxidizers, methanogens and sulfate reducers is present. Similarities between the hydrochemistry and potential connectivity of Hospital Hole and the Floridan Aquifer coastal mixing zone suggest that microbial communities of Hospital Hole could be a surrogate for the coastal mixing zone of the aquifer in the absence of direct studies. Understanding how groundwater microbial communities react to saltwater intrusion and nutrient flux will be useful in predicting how coastal aquifer regions might react to anthropogenic change.

Estimating the water budget in a semi-arid region (Torrevieja aquifer—south-east Spain) by assessing groundwater numerical models and hydrochemical data

The driest area of Europe is located in the south-east of Spain. In this region, water plays an essential role for the development and maintenance of the major economical engines for society, tourism and agriculture. In the coastal areas, water scarcity increases the risk of saltwater intrusion connected also to the overexploitation of aquifers. The adequate management of coastal aquifers requires to integrate climatic and hydrogeological information, but it is common to find incomplete datasets and uncertainties about the sources and sinks of water. The Torrevieja coastal aquifer gathers all these challenges with limited information available and essential questions about the aquifer functioning. The water budget has an imbalance between inputs from precipitation–irrigation return and outputs connected to water supply pumping for population and agriculture. Initial estimates indicate an annual deficit of 4.36 Mm3 that would produce short-term changes in the hydrodynamic system. However, the aquifer has been continuously exploited for the last 30 years which indicates the necessity of reviewing the hydrogeological characteristics of the region. A set of new conceptual models has been tested with numerical models to present alternative possibilities about the hydrogeological functioning combined with the analysis of hydrochemical data. The evaluation of the conceptual models revealed that up to 75% of the groundwater being extracted could proceed from a lower aquifer that has not been monitored. The improved water budget indicated a much lower annual deficit in the Torrevieja aquifer (0.2–0.8 Mm3) occasionally positive in years with high precipitation but introduces new questions about the recharge and origin of groundwater in the lower aquifer. In semi-arid areas, water is crucial facing climatic change and desertification processes; in this work, it is presented how the use of numerical models combined with hydrochemical information is a useful approach to provide new perspectives and improve water management.

Hydrogeology of the Sterkfontein Cave System, Cradle of Humankind, South Africa

Abstract A water level rise of almost 3 m in the space of two years in the Sterkfontein Cave system since late-2009 necessitated the re-routing of the tourist path through the cave to successively higher elevations on three occasions. It also raised concern for a possible association with copious acidic and sulphate-rich mine water drainage from the West Rand Goldfield (a.k.a. Western Basin) starting in early-2010, and the related threat to the UNESCO-inscribed fossil site. Although these circumstances have had little impact on the tourist value of the site, a prognosis of the impact on cave water level and quality is indicated by virtue of its karst setting and palaeontological significance. Historical and recent potentiometric data, together with ancillary hydrogeological and hydrochemical information acquired in the course of a water resources monitoring programme for the broader Cradle of Humankind World Heritage Site, provides new insight into the hydrogeology of the cave system. An improved understanding of the hydrophysical and hydrochemical response of the cave water system sheds light on the location of this system within the water resources environment. It is proposed that the present-day maximum cave water level is constrained to an elevation of ~1440 m above mean sea level. The recent electrical conductivity of 78 mS/m for cave water is 32% greater than the 59 mS/m recorded in mid-2010 and earlier. Similarly, the recent sulphate concentration of 161 mg/L is 178% greater than the 58 mg/L recorded before 2010. Compared to coeval values for ambient karst groundwater represented by the normative Zwartkrans Spring water, the magnitude of the increases in the springwater are similar, viz. 48% (from 84 to 124 mS/m) in salinity and 166% (from 154 to 409 mg/L) in sulphate. Although a distinct mine water impact is evident in both instances, the values indicate a muted impact on the cave water chemistry compared to the springwater. These and other documented observations better inform the threat from various poorer quality water sources to the fossil site in particular, and to the broader karst water resource in general. This contextualises concern for the hydroenvironmental future of Sterkfontein Cave and other nearby fossil sites such as Swartkrans, Rising Star and Bolt’s Farm. The dynamic response of the water resources environment to a variety of hydrological and hydrogeological drivers reinforces the need for monitoring vigilance across a range of disciplines.

CARACTERIZAÇÃO DE PROCESSOS HIDROGEOQUÍMICOS EM ÁGUAS SUBTERRÂNEAS DO SISTEMA AQUÍFERO SANTA MARIA, NA REGIÃO CENTRAL DO RIO GRANDE DO SUL

A study was carried out of the hydrogeochemical processes involving the groundwater of the western portion of the Santa Maria Aquifer System (SMAS) in the central region of Rio Grande do Sul. The objective of this study was to characterize the behavior of a portion of the groundwater between São Pedro do Sul, Santa Maria and Restinga Seca municipalities, based on a model between water/rock interaction. Mineralogical and hydrochemical information were analyzed, aiming to model the hydrogeochemical evolution of the aquifer in these municipalities. For this purpose, a processing of the information in a geochemical modeling code was performed, using as previous reference mineralogical studies. The results pointed out the main geochemical interactions responsible for groundwater chemistry, which is strongly dependent of the chemical composition of the recharge waters and the mineralogical contribution of the sedimentary rocks of this aquifer system. The groundwater saturation states showed subsaturation processes tending to the balance of carbonate minerals, indicating the dissolution of these minerals, mainly calcite, as well as supersaturation of clay-minerals ilite, montmorillonite (smectite) and kaolinite, in both cases tending to the alkalinization of the environment. The characterization of the hydrogeochemical properties of aquifers is important for a correct understanding of the processes that occur in it and dominate the regional hydrogeology.

Relação entre padrões hidroquímicos e as profundidades de fraturas com entra-das de água em rochas vulcânicas ácidas da formação serra geral

Este trabalho buscou avaliar a existência de diferentes padrões hidroquímicos dos aquíferos fraturados do Sistema Aquífero Serra Geral (SASG), relacionando esses padrões com as profundidades das entradas de água, no município de Carlos Barbosa-RS. Para este trabalho foram utilizadas informações hidroquímicas da água referentes a duas amostragens realizadas em 12 poços tubulares e 3 fontes. Para análise dos dados empregou-se os diagramas de Schoeller e Stiff, além da análise estatística de agrupamento, a fim de verificar padrões semelhantes entre os pontos amostrados. Observou-se uma boa correlação entre os padrões hidroquímicos e a profundidade das entradas de água, o que permitiu a elaboração de um modelo conceitual hidroquímico, onde foram identificadas águas com baixa concentração de íons em grupo de poços que possuem entradas de água localizadas em profundidades inferiores a 30 metros. Também foi identificado um grupo de poços cujas entradas de água estão localizadas entre 50 e 112 metros e apresentam águas com maior concentração de íons como cálcio, sódio, bicarbonatos. A explicação dessas diferenças pode estar relacionada com a circulação de água e com tempo de interação água-rocha que ocorre de forma diferente dependendo da profundidade das entradas de água.

Using airborne EM and borehole NMR data to map the transmissivity of a shallow semi-confined aquifer, western NSW

SUMMARY The Broken Hill Managed Aquifer Recharge (BHMAR) project aimed to define key groundwater resources and aquifer storage options in the lower Darling River floodplain of western NSW. The project was multidisciplinary and utilised airborne electromagnetics (AEM), borehole nuclear magnetic resonance (NMR) and LiDAR DEM data and lithological, hydrostratigraphic and hydrochemical information to develop a suite of hydrogeological and groundwater property maps and products. This abstract discusses the methods and results of estimating the transmissivity of the semi-confined target aquifer. Hydrostratigraphy and hydraulic texture classes were mapped by interpreting the AEM data in conjunction with borehole geophysics and lithological information. Aquifer transmissivity was statistically derived by combining borehole NMR hydraulic conductivity estimates with the mapped 3D distribution of texture classes and hydrostratigraphic units. Using a statistical and GIS approach, the derived aquifer thicknesses in the key areas ranged from 20 - 40 m and the lower and upper transmissivity bounds ranged from 1 to 10 m 2 /d, and 10 m 2 /d to 1000 m 2 /d, respectively.