Search

Free aquifers have become an important water supply option for underdeveloped and developing countries, due to the resource quality and relatively low extraction prices. However, overexploitation and the lack of territorial planning guidelines in these areas endanger groundwater availability and quality. In this context, this study aimed to analyze the vulnerability to groundwater contamination and contribute to the conservation of the ecosystem services, provided by the Guarani aquifer in Brotas, Brazil, by applying the PESTICIDE-DRASTIC-LU model. The application of this model allowed the identification of priority conservation areas within the context of ecosystem services that groundwater provides to local inhabitants. To this end, we collected, treated, and analyzed seven different hydrogeological data to understand the environmental dynamics of the system and to identify which areas are most vulnerable to aquifer contamination. The results pointed out that 64% of the study area presents zones of high and very high vulnerability to contamination, due to the local hydrogeological characteristics (sandy soils and rocks) and the various anthropogenic activities, mainly with large plantations of sugar cane and eucalyptus. In addition, the mapping allowed the spatial demonstration of the places that should be considered a priority for the conservation of ecosystem services provided by local groundwater. Thus, our results can serve as a baseline to define public action strategies for the preservation and sustainable management of the Guarani aquifer areas. [ABSTRACT FROM AUTHOR]

Free aquifers have become an important water supply option for underdeveloped and developing countries, due to the resource quality and relatively low extraction prices. However, overexploitation and the lack of territorial planning guidelines in these areas endanger groundwater availability and quality. In this context, this study aimed to analyze the vulnerability to groundwater contamination and contribute to the conservation of the ecosystem services, provided by the Guarani aquifer in Brotas, Brazil, by applying the PESTICIDE-DRASTIC-LU model. The application of this model allowed the identification of priority conservation areas within the context of ecosystem services that groundwater provides to local inhabitants. To this end, we collected, treated, and analyzed seven different hydrogeological data to understand the environmental dynamics of the system and to identify which areas are most vulnerable to aquifer contamination. The results pointed out that 64% of the study area presents zones of high and very high vulnerability to contamination, due to the local hydrogeological characteristics (sandy soils and rocks) and the various anthropogenic activities, mainly with large plantations of sugar cane and eucalyptus. In addition, the mapping allowed the spatial demonstration of the places that should be considered a priority for the conservation of ecosystem services provided by local groundwater. Thus, our results can serve as a baseline to define public action strategies for the preservation and sustainable management of the Guarani aquifer areas.

Petrographic analyses are presented for the Rivera, Tacuarembó and Cuchilla Ombú formations, which constitute the outcropping Guaraní Aquifer System in the Rivera and Tacuarembó departments, Uruguay. Sedimentary petrography studies were carried out with the objective of qualitatively and quantitatively evaluate the porosity of sedimentary rocks. To determine the porosity in sandstones, the method of impregnation of petrographic thin sections followed by point-counting of total pore area and interconnected pore area was used. Clast and matrix composition was determined using both optical microscope and scanning electron microscope (SEM), with an energy dispersive X-ray analyzer (EDS) The study shows average values of total porosity of 17% and effective porosity of 14% for the Rivera and Cuchilla Ombú aquifer units and average value of total porosity of 15% and effective porosity of 9% for the Tacuarembó unit. There are compositional differences between sandstones of the Rivera and Tacuarembó formations, the former being essentially quartz-arenites and the latter predominantly subarkoses and sublithic arenites.

Fascinating circular hydrothermal bowls 0.5 m in diameter occur in paleodunes of the 1.2 million km2 Botucatu paleoerg in the Fronteira Oeste of Brazil, Rio Grande do Sul, and were exposed upon erosion of presumed 2,000 m of basalt and rhyodacite cover of the Paraná Volcanic Province (1 million km2) since the Cretaceous (135 Ma). The tops of the paleodunes display low-temperature (150-50°C) hydrothermal structures comparable to those in basalts and rhyodacites. The source beds of sand injectites display evidence of sequential fault-valve action. The bowls represent a new structure in continental paleodunes. They present circular rims sealed by quartz and a flat horizontal bottom with a central sealed vent. The inclined internal rims of the bowls exhibit a radial set of linear fractures filled with quartz, forming prominent, sharp, positive structures. Their origin is ascribed to the work of water vapor originated in the heated freshwater aquifer. The concave ceiling was lifted a few millimeters along circular fractures long enough for quartz to be deposited. Erosional exhumation of the buried Botucatu hyperdry sand sea has revealed the effects, including the new structures described here, of hydrothermalism associated with a major igneous province upon a giant paleoerg turned-aquifer. [ABSTRACT FROM AUTHOR]

The research sought to understand how the Water Resources Legislation addresses the management of outcrop areas of the Guarani Aquifer System in the state of São Paulo, specifically in the Pardo and Tietê/Jacaré Water Resources Management Units. Therefore, a bibliographical review was carried out regarding the Brazilian and São Paulo laws of water resources, as well as a documentary research in the portal of the System of Information and Management of Water Resources. As a main result it was possible to verify that groundwater, mainly in the outcrop area of the SAG, is still superficially addressed, and there is no guarantee that the integrated and decentralized management of water resources will be effectible apply.

The control and extraction of natural resources throughout the world --like water-- is part of the global strategy of the United States of America in order to maintain a hegemonic position in the commodities market in energy, agriculture or mining exploitation sectors. This text studies the United States interests and those of global companies supported by them in relation to the water resource located in Paraguayan territory called Guaraní Aquifer (being of high geostrategic importance); it also analyzes the current national Paraguayan regulation that can guarantee the public ownership and management of water, avoiding the penetration and preponderance of private or foreign interests. [ABSTRACT FROM AUTHOR]

This paper estimated the total water storage variation in the southern rim of the Guarani Aquifer System during a three-year time span, making use of data provided by the Gravity Recovery and Climate Experiment. Monthly data were used to estimate the Bouguer anomaly in Southern Brazil. A direct modeling, using the Bouguer plateau, was applied to quantitatively estimate the water volume variation of a specific thickness in the studied region. Meteorological almanac data were compared to the gravitational alterations. We found a direct proportionality between the monthly rain average and the water table level. A simple model was found to forecast water accumulation as a function of rainfall regime, which is validated by a Pearson index of 0.82 that indicates a strong correlation between pluviometric and gravimetric data. In order to raise the stored water level near the recharge area by 1 mm, approximately 3 mm of rainfall is needed. [ABSTRACT FROM AUTHOR]

Copyright of Revista Jurídica (0103-3506) is the property of Revista Juridica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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

Highlights • This article explores convergences between the concept of scale in human and physical geography. • It examines Brazil's exertion of hydro-hegemonic power in South America. • It contributes to assessments of water politics in South America via a production of scale approach. • The article analyses the array of social interactions to produce hydropolitical scales. Abstract This article analyses the production of scale in the La Plata River Basin and Guarani Aquifer System within regional hydropolitics in South America. We argue that different political and ecological scales acquire prominence according to the national political goals at stake, reproducing multi-scalar politics within and beyond South America. To support this argument, this article presents a literature review on the concept of scale in geography that explores the production of, and interaction among scales. The article then takes a historical approach to the evolving scales associated with the cases of the La Plata River Basin and Guarani Aquifer System to show how Brazil exerts hydropolitical regional hegemony through the construction of infrastructure and signing of agreements and treaties. Rather than a simple case of conflict or cooperation over water resources, these episodes represent a continuum of political interactions engendered by specific political goals and involving different social actors. [ABSTRACT FROM AUTHOR]

Abstract: Recharge areas of the Guarani Aquifer System (GAS) are particularly sensitive and vulnerable to climate variability; therefore, the understanding of infiltration mechanisms for aquifer recharge and surface run‐off generation represent a relevant issue for water resources management in the southeastern portion of the Brazilian territory, particularly in the Jacaré‐Pepira River watershed. The main purpose of this study is to understand the interactions between precipitation, surface water, and groundwater using stable isotopes during the strong 2014–2016 El Niño Southern Oscillation event. The large variation in the isotopic composition of precipitation (from −9.26‰ to +0.02‰ for δ18O and from −63.3‰ to +17.6‰ for δ2H), mainly associated with regional climatic features, was not reflected in the isotopic composition of surface water (from −7.84‰ to −5.83‰ for δ18O and from −49.7‰ to +33.6‰ for δ2H), mainly due to the monthly sampling frequency, and groundwater (from −7.04‰ to −7.76‰ for δ18O and from −49.5‰ to −44.7‰ for δ2H), which exhibited less variation throughout the year. However, variations in deuterium excess (d‐excess) in groundwater and surface water suggest the occurrence of strong secondary evaporation during the infiltration process, corresponding with groundwater level recovery. Similar isotopic composition in groundwater and surface water, as well as the same temporal variations in d‐excess and line‐conditioned excess denote the strong connectivity between these two reservoirs during baseflow recession periods. Isotopic mass balance modelling and hydrograph separation estimate that the groundwater contribution varied between 70% and 80%, however, during peak flows, the isotopic mass balance tends to overestimate the groundwater contribution when compared with the other hydrograph separation methods. Our findings indicate that the application of isotopic mass balance methods for ungauged rivers draining large groundwater reservoirs, such as the GAS outcrop, could provide a powerful tool for hydrological studies in the future, helping in the identification of flow contributions to river discharge draining these areas. [ABSTRACT FROM AUTHOR]

Sponges harbor great diversity and an abundance of organisms. Although this community can vary temporally, and between and within sponge species, it is not known how an induced change in habitat-specific environmental conditions might affect the structure of macroinvertebrate assemblages associated with sponges. Here, a reciprocal transplant experiment of individuals of the estuarine sponge Halichondria melanadocia was conducted between two neighboring habitats (seagrass and mangrove prop root habitats) in the Southern Gulf of Mexico. Transplanted sponges experienced different hydrodynamic and light conditions. Multivariate analyses showed differences in community structure of associated assemblages among treatments, which were mainly driven by changes in the abundance of common species. Sponges moved from seagrass to mangrove habitat experienced a significant increase in abundance and taxonomic richness of 88 and 35%, respectively. Given that changes in the volume and aquiferous system (oscula diameter and density) of the hosts and in salinity were also recorded during the study period, it is concluded that the structure of the H. melanadocia-associated assemblages was not only influenced by the habitat change but also by other factors such as host morphology and short-term variations in the population abundance of associated organisms. [ABSTRACT FROM AUTHOR]

The aim of this work is to understand the exchange of water between the Serra Geral aquifer system (SGAS) and Guarani aquifer system (GAS). The objectives are two-fold. First, introduce the capability of the modified self-organizing maps (MSOM) as an unbiased nonlinear approach to estimate missing values of hydrochemistry and hydraulic transmissivity associated with the SGAS, a transboundary groundwater system spanning parts of four South American countries. Second, identify areas with potential connectivity of the SGAS with the GAS based on analysis of the spatial variability of key elements and comparison with current conceptual models of hydraulic connectivity. The MSOM is employed to calculate correlations (trends) between 27 variables from 1,132 wells. Hydraulic transmissivity is calculated from specific capacity values from well-pump tests in 157 locations. Hydrochemical facies estimates appear unbiased and consistent with current conceptualconnectivity models indicating that vertical fluxes from GAS are influenced by geological structure. The MSOM provides additional spatial estimates revealing new areas with likely connections between the two aquifer systems. [ABSTRACT FROM AUTHOR]

This article explores the governance of the Guarani Aquifer System (GAS) through the lens of critical hydropolitics and specifically through the framework of hydro-hegemony. This study is important as the GAS, which is one of the first examples of transboundary groundwater cooperation, has been studied through hydrological, geological and legal disciplinary approaches, but hydropolitical analyses of the issues raised in cooperation of this resource is still lacking. While a hydrological analysis of the GAS is important, it is not enough to comprehend and make sense of the governance and political agreements among the countries. For this reason, this article complements the existing studies on the hydrological, geological, and legal analyses published on this aquifer. By taking the case study of the GAS, this article makes important empirical contributions to the study of transboundary groundwater cooperation. This article argues that through critical hydropolitics, and in particular by consideration of the power asymmetries between states and their exploitation potential of groundwater, it is possible to more accurately understand the current water governance’s arrangements around the GAS. It also argues that critical hydropolitics fails to explain informal cooperation arrangements in the case of the GAS. [ABSTRACT FROM AUTHOR]

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in several products, although they can act as neurotoxic, hepatotoxic and endocrine disruptors in organisms. In Brazil, their levels in aquatic sediments are poorly known; thus, concerns about the degree of exposure of the Brazilian population to PBDEs have grown. This study aimed to quantify the presence of PBDEs in sediment samples from an important groundwater water supply in Ribeirao Preto, Brazil, and to contribute to studies related to the presence of PBDEs in Brazilian environments. Gas chromatography coupled with Electron Capture Detection (GC-ECD) was used for quantification after submitting the samples to ultrasound-assisted extraction and clean-up steps. Results showed the presence of six PBDE, BDE-47 being the most prevalent in the samples, indicating a major contamination of the penta-PBDE commercial mixture. The concentration of ΣPBDEs (including BDE-28, -47, -66, -85, -99, -100, -138, -153, -154 and -209) varied between nd (not detected) to 5.4 ± 0.2 ng g−1. Although preliminary, our data show the anthropic contamination of a direct recharge area of the Aquifer Guarani by persistent and banned substances.

Abstract International cooperation on groundwater takes many forms. The mobilization of different actors helps to promote cooperation initiatives in South America, where the most well known case is the Guarani Aquifer System (GAS). This article intends to analyze how international actors have motivated cooperation on transboundary aquifers and its repercussions in South America, especially in the case of the GAS.

The city of Ribeirão Preto, SP, is fully supplied by groundwater from the Guarani aquifer. The city has a total of 102 public supply wells registered in the Ribeirão Preto Water and Sewage Department, approximately 13,400 m³/h of water are uptaken from them. Some wells are located in the recharge area of the Guarani Aquifer, a region susceptible to anthropogenic pollution. This study aimed to evaluate the quality of water of public supply wells in Ribeirão Preto considering specific chemical parameters including pH, metals and nitrate. Three sampling collections were performed in 33 wells for water supply in Ribeirão Preto, in May and November 2008, and in July 2009, as well. Analyses of the metals Fe, Zn, Mn, Cr, Pb, Cu and Cd were performed using the Induced Plasma Spectroscopy technique (ICP-OES). The analyses of nitrate concentration were performed using spectrophotometric method. Regarding the metals and nitrate parameters, all samples were within the values established by the ordinance of the Ministry of Health No. 518 of 2004. Regarding pH, a small number of wells had pH below the limit of drinkable water, but values were very close to the lower limit established by the ordinance. Water of public supply wells in Ribeirão Preto are, in general, of good quality, showing no restrictions for use. Nevertheless, continuous monitoring of all public supply wells is necessary, especially regarding the presence of nitrate and chromium, second report of Company of Technology and Environmental Sanitation – Cetesb.

Este trabalho analisa a situação institucional do Mercosul em relação à gestão compartilhada dos recursos hídricos a partir do Sistema Aqüífero Guarani, importante reservatório de águas subterrâneas que ocorre no território da Argentina, do Brasil, Paraguai e Uruguai. Inicialmente é apresentado o quadro físico do aqüífero. Em seguida, são expostos os instrumentos de gestão ambiental do Mercosul e a pertinência em deslocar para esse bloco de países a coordenação do uso do Sistema Aqüífero Guarani - SAG. Ele teve como base uma pesquisa documental e a literatura sobre o tema.This study examines the institutional situation of Mercosur in relation to the management of shared water resources from the Guarani Aquifer System, an important reservoir of groundwater that occurs in the territory of Argentina, Brazil, Paraguay and Uruguay. Initially is displayed the physical conditions of the aquifer. Then they are exposed to environmental management tools and relevance in the Mercosur move to this block of countries to coordinate the use of the Guarani Aquifer System - SAG. It was based on a documentary research and literature on the subject.

We present a model of a polluted groundwater site. The model consists of a coupled system of advection-diffusion-reaction equations for the groundwater level and the concentration of the pollutant. We use the complete flux scheme for the space discretization in combination with the ϑ-method for time integration and we prove a new stability result for the scheme. Numerical results are computed for the Guarani Aquifer in South America and they show good agreement with results in literature. [ABSTRACT FROM AUTHOR]

The Guarani Aquifer Accord of 2010 represents a plan for the multiple, sustainable, equitable and reasonable use of the water of the Guarani Aquifer System and a pledge to prevent significant harm to this vast natural resource in South America. Based on good science and good international law, this regional agreement was reached by Brazil, Argentina, Uruguay and Paraguay, acknowledging the environmental, economic and geopolitical importance of the underground water linking the four states known as the "Guarani Aquifer System." The Guarani Aquifer Accord ("Acordo sobre o Aquífero Guarani" or "Acuerdo Aquífero Guarani") is the first regional treaty to be modeled after the International Law Commission Draft Articles on Transboundary Aquifers of 2008, which address "confined" aquifers that are outside the scope of the United Nations Watercourses Convention of 1997. This article explores the Guarani Aquifer Accord's provisions for exchanges of scientific and technical information, notification and consultation, direct negotiations, referral to a joint commission to be created once the Accord enters into force for evaluation and recommendations in case of a dispute, and the option of a subsequent arbitration protocol to be negotiated in future. Taken together, procedural requirements and the provisions in the Accord in favor of diplomatic and political resolution of future disputes over the use and protection of the water may forestall the need to resort to litigation in international courts or tribunals. This article concludes that, even absent an additional protocol for arbitration of disputes and absent the establishment of a joint commission to facilitate information exchange, convene regular meetings and build trust as contained in the agreement, the Guarani Aquifer Accord provides a framework for regional cooperation designed to avoid or resolve conflicts. [ABSTRACT FROM AUTHOR]

The Guarani Aquifer System (GAS) is a subsurface reservoir that contains the largest volume of fresh groundwater in South America. Despite the relevance of the GAS, a lack of attention has been paid to land use effects on its recharge. We present the most detailed long-term (2004–2011) results of land-use effects on recharge in an outcrop area of the GAS. Water table fluctuations (WTFs) were measured at 11 monitoring wells, which are distributed between different land uses (i.e. eucalyptus, sugarcane, citrus and grassland). Recharge was estimated using a point-scale method (WTF) for each monitored well. The annual recharge estimates for different land uses are eucalyptus forest (135 mm year-1), sugarcane (248 mm year-1), citrus areas (296 mm year-1) and grassland (401 mm year-1). The results indicate that the evapotranspiration seems to be a key parameter in the assessment of recharge in the study area. [ABSTRACT FROM PUBLISHER]

International cooperation on groundwater takes many forms. The mobilization of different actors helps to promote cooperation initiatives in South America, where the most well known case is the Guarani Aquifer System (GAS). This article intends to analyze how international actors have motivated cooperation on transboundary aquifers and its repercussions in South America, especially in the case of the GAS. [ABSTRACT FROM AUTHOR]

International law governing transboundary aquifers is considerably underdeveloped, with only a handful of bilateral and multilateral agreements governing specific aquifer systems to date. However, the significance of transboundary aquifers in addressing water security concerns is gaining recognition, and dialogue discussing the future of the international legal framework is growing in importance. Contributing to this dialogue, we seek to compare different legal instruments applicable to the management of transboundary aquifers in different regions. We draw from the experience of the processes that led to an established transboundary agreement in one region, and compare it to another region that is yet to establish a formal legal instrument. Specifically, we compare the Guarani Aquifer System in Latin America with international legal instruments applicable to the management of transboundary aquifers in the Southern African Development Community ( SADC). We identify several trends arising from the management of the Guarani Aquifer System that could have potentially valuable input for SADC countries currently embarking upon the initial stages of the management of a transboundary aquifer. Central to this article is the underlying question of whether these international legal instruments, which are placed in dramatically different contexts, can be compared in the first place. We conclude that such a comparison is useful only if undertaken as a process of knowledge acquisition, as such a broad comparative exercise is limited in its ability to produce direct policy recommendations. Gaining knowledge of regional governance practices in relation to differing aquifer characteristics is particularly important in this underdeveloped area, especially as discussions regarding the future for transboundary aquifer law are gaining momentum at the international level. [ABSTRACT FROM AUTHOR]

In crop farms, it is common to use animal livestock manure as soil biofertilizer, as well as agricultural defensives that can reach to ground and surface waters. Waterborne microorganisms as Salmonella and Escherichia coli can cause gastroenteritis to consumers, and the presence of chemical compounds can cause DNA mutation damages in exposed organisms. Thus, the present study aimed at quantifying E. coli and Salmonella in surface water from the Suruvi river (located above the Guarani aquifer) and evaluating the water genotoxic potential using Allium cepa as a model. For that, five sampling sites were established, and water samples were collected from March/2013 to June/2014, and submitted to bacteria enumeration, and genotoxicity assay. Moreover, rainfall volume and air temperature were measured. Results indicated the occurrence of Salmonella in 14 % of the samples and high amounts of E. coli (>1875 MPN/100 mL). The amount of E. coli decreased as the rainfall volume increased. The genotoxicity assay results showed that water contains substances, which are able to induce changes in mitotic index on the root meristem cells of A. cepa. In summary, surface water sources are contaminated with fecal material and genotoxic substances, emphasizing the importance of surveillance of surface and groundwater in this region, especially because of the proximity to the Guarani aquifer. [ABSTRACT FROM AUTHOR]

The increasing demand for natural resources, for agricultural use and urban development, could advance towards areas with possible risk of groundwater contamination, because they are not well planned and/or inadequate environmental studies appropriate to a particular condition of use. This situation is related to the natural vulnerability that evaluates soil type, geology, slope and permanent preservation area; identified as environmental conflicts, due to inappropriate activities, in areas with potential risk of groundwater contamination. Thus, the objectives of this study were to conduct a survey of potentially contaminating activities and to relate their areas of influence with the map of natural vulnerability, which defines the interrelationship among soil maps, geology, slope the municipality of Faxinal do Soturno -- RS, Brazil to check possible improper soil use. For this purpose, data were collected from wells and a potentiometric surface map was generated from the static level of wells, which allowed the estimation of groundwater flow. In the municipality, potential activities, including cemeteries, hospitals, fuel station, brick kilns and sawmills with potential risk of contamination were identified. With available technical procedures, potentially contaminating activities were identified in areas of medium and high vulnerability, which characterizes the possible risk of contaminating the groundwater in the municipality in question. [ABSTRACT FROM AUTHOR]

The Guarani Aquifer System (GAS) is the largest transboundary groundwater reservoir in South America, yet recharge in the GAS outcrop zones is one of the least known hydrological variables. The objective of this study was to assess the suitability of using remote sensing data in the water-budget equation for estimating recharge inter-annual patterns in a representative GAS outcropping area. Data were obtained from remotely sensed estimates of precipitation ( P) and evapotranspiration (ET) using TRMM 3B42 V7 and MOD16, respectively, in the Onça Creek watershed in Brazil over the 2004-2012 period. This is an upland flat watershed (slope steepness <1 %) dominated by sandy soils and representative of the GAS outcrop zones. The remote sensing approach was compared to the water-table fluctuation (WTF) method and another water-budget equation using ground-based measurements. On a monthly basis, the TRMM P estimate showed significant agreement with the ground-based P data ( r = 0.93 and RMSE = 41 mm). Mean(±SD) satellite-based recharge ( R) was 537(±224) mm year. Mean ground-based recharge using the water-budget ( R) and the WTF ( R) methods were 469 mm year and 311(±75) mm year, respectively. Results show that 440 mm year is a mean (between R, R and R) recharge for the study area over the 2004-2012 period. The latter mean recharge estimate is about 29 % of the mean historical P (1,514 mm year). These results are useful for future studies on assessing recharge in the GAS outcrop zones where data are scarce or nonexistent. [ABSTRACT FROM AUTHOR]

The Capiibary catchment, SE Paraguay, forms part of the Guarani Aquifer System and is intensively used for cashcrop agriculture (soy bean, wheat, maize), with two or more harvests per year. The aim of this study was to investigate the effects of no-till agriculture with frequent herbicide and fertilizer applications on groundwater quality under subtropical climate. Water samples taken from 81 wells showed rather low nutrient (e.g. nitrate) concentrations, probably due to the high humus content of the no-till soils and the prevalent climatic conditions which allow constant microbial recycling of nutrients. The denitrificaton potential of the aquifer is, however, small. Further analysis in seven wells showed no indication of pesticides in groundwater. This is probably attributable to a combination of the effects of no-till agriculture and the subtropical climate. [ABSTRACT FROM AUTHOR]

To understand transboundary groundwater governance in the South American Guarani Aquifer System, we surveyed global and regional experts about the region’s groundwater quantity and quality, ownership and rights, and regulation and administration. Respondents (1) perceived groundwater quality and withdrawal as under-regulated, and relevant information and data as inadequate; (2) suggested that contamination and overdrafting remain mostly incipient and localized along international borders; and (3) viewed groundwater as a shared resource administered by the state for the public, rather than as private property. Respondents suggested that while there is progress towards implementing a formal transboundary aquifer agreement, local-to-national-scale governance is important. [ABSTRACT FROM PUBLISHER]

Radiogenic 4He is produced by the decay of uranium and thorium in the Earth's mantle and crust. From here, it is degassed to the atmosphere and eventually escapes to space. Assuming that all of the 4He produced is degassed, about 70% of the total 4He degassed from Earth comes from the continental crust. However, the outgoing flux of crustal 4He has not been directly measured at the Earth's surface and the migration pathways are poorly understood. Here we present measurements of helium isotopes and the long-lived cosmogenic radio-isotope 81Kr in the deep, continental-scale Guarani aquifer in Brazil and show that crustal 4He reaches the atmosphere primarily by the surficial discharge of deep groundwater. We estimate that 4He in Guarani groundwater discharge accounts for about 20% of the assumed global flux from continental crust, and that other large aquifers may account for about 33%. Old groundwater ages suggest that 4He in the Guarani aquifer accumulates over half- to one-million-year timescales. We conclude that 4He degassing from the continents is regulated by groundwater discharge, rather than episodic tectonic events, and suggest that the assumed steady state between crustal production and degassing of 4He, and its resulting atmospheric residence time, should be re-examined. [ABSTRACT FROM AUTHOR]

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

Groundwater economic models have refined optimal extraction rules while lagging behind in the study of optimal spatial policies. This paper develops a theoretical model to estimate welfare gains from optimal groundwater management when the choice variable set is expanded to include well location decisions as well as optimal groundwater extraction paths. Our theoretical results show that if there is spatial heterogeneity in groundwater, the welfare gains from optimal location of wells are substantial even if extraction rates are unregulated. Furthermore, second-best economically defined spacing regulations may possibly have better efficiency results (and lower implementation costs) than first-best uniform taxes or quotas. An application of the model to a real-world aquifer shows the importance of including well location decisions in spatially differentiated groundwater models and the need for (1) robust estimates of the gains from optimal management and; (2) spatially explicit regulations. [ABSTRACT FROM AUTHOR]

Abstract: Like other regions around the world, southern Brazil has experienced periods of drought, having to find alternative water resources for producing drinking water during these times. The deep wells drilled in the Guarani Aquifer could help with this water imbalance, but the water, in some places, is brackish. This work is an exploratory study of the use of the brackish water from the Guarani Aquifer as an alternative supply for drinking water, using reverse osmosis to reduce the content of F−, SO4 2− and TDS (Total Dissolved Solids). The desalinated water obtained from reverse osmosis at a pressure of 2MPa and a cross-flow velocity of 1.61m.s−1 showed rejections of approximately 94% for SO4 2−, 97% for TDS and 100% for F−. Blended water, produced by mixing groundwater and permeate, was proposed to optimize the produced drinking water with a recovery rate of 93%. Reverse osmosis is an excellent alternative for the supply of water in southern Brazil. [Copyright &y& Elsevier]

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

This paper presents a geological model of Corrientes province (Argentina) based on Bouguer gravity anomaly data, obtained in 2073 measurement points. To build the model, the IGMAS+ interactive program was used. Two areas of approximately 135,000km2 were modeled in this study. The selection of these areas was based on the sectors where the largest number of gravity anomaly measurements was made and other type of data was available to perform the parameterization (i.e, lithology profiles in boreholes, seismic profiles and audio-magnetotelluric AMT soundings). The initial geological configuration proposed was composed by four layers: basement, sediments (Paleozoic–Lower Cretaceous), basalts (Serra Geral Group, Lower Cretaceous) and post-basaltic sediments. The result shows a basement compartmentalized in structural blocks separated by large faults. The connection of Asunción and Río Grande Arches is confirmed along a structural high that crosses Corrientes province from SE to NW. The basaltic layer shows lateral changes in its thickness, due to faulting, almost disappearing on the NW of Corrientes. This structural configuration has a special hydrogeological importance because it produces the rise of the Guaraní Aquifer System sedimentary series near the surface and the intense fracture network makes this area prone to local recharge and regional discharge. [ABSTRACT FROM AUTHOR]

The Guarani Aquifer System includes six Brazilian states and smaller areas in Paraguay, Uruguayand Argentina. It consists predominantly of Mesozoic siliciclastic sediments of aeolian and fluvial origin in Brazilreferred to as the Pirambóia and Botucatu formations, in the Parana Basin. Regarding its stratigraphic compartments, theaquifer presents three main flow units that are identified and named after the genetic facies: dune, interdune and channelones. The structural compartmentation of the aquifer was defined from integration of previously publishedmorphostructural maps drawn from radar, satellite, digital elevation model, and also regional aeromagnetometric andgravimetric data. The main goal of the present study was to establish the structural and stratigraphical control of theaquifers regional hydrodynamics and hydrochemistry. From the flow units identified, the mean hydraulic conductivity ofthe aquifer was determined based on its sediments selection, granulometric and clay content. Top and bottom values ofthe hydrostratigraphic units were interpolated by using structural lineaments as break lines. Once the flow units and thestructural compartmentation of the aquifer were defined and its spatial variations known, its dynamic potential flowpatterns were identified, which revealed the strong structural influence on its hydrodynamics and hydrochemistry. Thepotential flow maps and the flow direction maps obtained may help in the delimitation of preferential recharge anddischarge areas as they depict a hydraulic conductivity zoning and the structural and stratigraphic control of the systemsinput and output.

Abstract: La Plata Basin (LPB) is situated in Argentina, Bolivia, Brazil, Paraguay and Uruguay, is one of the largest catchment in South America, extending over 3.1millionkm2, has enormous economic and social importance for the region. The Guarani Aquifer System (GAS) is located in the eastern and midsouthern South America and underlies in some areas of Argentina, Brazil, Paraguay and Uruguay, with an estimated total surface about 1,090,000km2. Most of the GAS area is located in the LPB. The Global Environment Facility (GEF) has supported several programs in the LPB region. Among them, the Framework Program for the Sustainable Management of the Water Resources of the La Plata Basin with respect to the Effects of Climate Variability and Change (LPB Project) and the Environmental Protection and Sustainable Development of the Guarani Aquifer System Project (GAP). Experiences gained during the development of the GAP have provided learning opportunities that could be useful in the implementation of new GEF projects, particularly the LPB Project. This paper draws primarily upon lessons learned from the GAP that are currently being considered in the LPB Project. [Copyright &y& Elsevier]

High fluoride concentrations (up to 11 mg/L) have been reported in the groundwater of the Guarani Aquifer System (Santa Maria Formation) in the central region of the state of Rio Grande do Sul, Southern Brazil. In this area, dental fluorosis is an endemic disease. This paper presents the geochemical data and the combination of statistical analysis (Principal components and cluster analyses) and geochemical modeling to achieve the hydrogeochemistry of the groundwater and discusses the possible fluoride origin. The groundwater from the Santa Maria Formation is comprised of four different geochemical groups. The first group corresponds to a sodium chloride groundwater which evolves to sodium bicarbonate, the second one, both containing fluoride anomalies. The third group is represented by calcium bicarbonate groundwater, and in the fourth, magnesium is the distinctive parameter. The statistical and geochemical analyses supported by isotopic measurements indicated that groundwater may have originated from mixtures of deeper aquifers and the fluoride concentrations could be derived from rock/water interactions (e.g., desorption from clay minerals). [ABSTRACT FROM AUTHOR]

It has been determined that the fluorine concentration reaches up to 11 mg L in the porous-confined Santa Maria Aquifer, Guarani Aquifer System, in the central region of the state of Rio Grande do Sul, southern Brazil. Due to the elevated fluorine content in the groundwater, which is the major supply for drinking water, several incidences of dental fluorosis occurred. This area is the largest tobacco producer in Brazil and has a long history of fertilizer application. The fluorine in the local groundwater is likely to have come from the use of apatite-based fertilizers. This hypothesis was tested by soil and water analyses. Fluorine concentration has been monitored in the field for 2 years. The data combined with laboratory experiments on the adsorption and leaching of fluorine in soils showed that fluorine is easily retained by adsorption on aluminum clay-rich soils (Udults). The local clay-rich soils present high cation exchange capacity, aluminum content, and low pH; they act as a trap for fluorine derived from fertilizer and play an important role in the mobility of fluorine. [ABSTRACT FROM AUTHOR]

The article focuses on the extreme challenges of Guarani Aquifer System (GAS) arising from the significant impact of Brazilian legal regime forms. It analyzes the multilateral policy challenges to the GAS that arisen from internal and external threat and proposes a combating strategy. It offers an international dispute resolution framework drawn from U.S. water law and depicts amendment to the jurisdiction to resolve disputes challenging the GAS.