Estimativa da vulnerabilidade natural de aqüíferos: uma contribuição a partir da resistividade e condutância longitudinal

Este trabalho descreve os resultados obtidos com o método da eletrorresistividade usando a técnica da sondagem elétrica vertical (arranjo Schlumberger) aplicada em estudos ambientais envolvendo as águas subterrâneas. A vulnerabilidade natural de aqüíferos, importante ferramenta em estudos ambientais, pode ser estimada a partir de métodos geoelétricos, cujos parâmetros resistividade e condutância longitudinal, aliados ao tipo de ocorrência dos aqüíferos (livre a confinado) e profundidade do nível d'água, permitiram obter um índice de vulnerabilidade natural correspondente ao normalmente utilizado. Os resultados, aplicados em uma fase preliminar de estudos, são bons, permitindo um melhor direcionamento e programação das fases posteriores.

Uso e gestão de águas subterrânea em Araguaína/TO

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

O uso de técnicas geoestatísticas para o mapeamento da vulnerabilidade natural do Aquífero Guarani em área de recarga: aplicação na região de Ribeirão Bonito - SP

Pós-graduação em Geociências e Meio Ambiente - IGCE

Mapeamento da condutividade hidráulica da cobertura do aquífero Guarani, situado na bacia hidrográfica dos rios Jacaré-Guaçú e Jacaré-Pepira, na porção centro-norte do estado de São Paulo

Given the importance of preserving the water quality of the Guarani Aquifer, the work done in the hydrographic basin of the rivers Jacaré-Guaçú e Jacaré-Pepira, located in the central-northern São Paulo state, was made to map the hydraulic conductivity from the use of some empirical methods associated with granulometric analysis and in situ testing, specifically with the Guelph permeameter. All results were submitted to a correlation analysis and subsequently mapped using the methodology of minimum curvature, based on numerical techniques Spline. These procedures provide for studies of aquifer vulnerability and assist in decision making in environmental projects and guidelines for urban planning

Mapeamento geoestatístico da vulnerabilidade do Aquífero Guarani no município de Ribeirão Bonito - SP

The Guaraní aquifer has relevant importance both as a source of water for several urban centres and the development of agriculture and livestock. In recharge areas the aquifer is free and, therefore, subject to contamination of effluents and tailings deposited on soils that cover it. Thus, it becomes crucial not only its protection at all levels, as the knowledge of its degree of natural vulnerability. The present work used geostatistics modeling techniques to study the natural vulnerability of the Guaraní aquifer in the city of Rio Bonito, State of São Paulo, southeastern Brazil, where the Guarani aquifer is exposed. These techniques, extensively used in evaluation studies of mineral deposits and oil tanks, can be adapted to produce a spatial classification or a regionalisation of probabilistic indices of vulnerability. By ordinary kriging method maps of vulnerability classification were obtained. To determine the vulnerability of the aquifer was employed the Aquifer Vulnerability Index (AVI), which requires knowledge of unsaturated zone thickness and permeability. The final product was a map with probabilistic index of vulnerability of the Guaraní aquifer, which presented values between 0 to 0.33 years, framing the area studied in AVI class extremely high vulnerability

Stochastic simulation of time-series models combined with geostatistics to predict water-table scenarios in a Guarani Aquifer System outcrop area, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Using neural networks for estimation of aquifer dynamical behavior

The systems of water distribution from groundwater wells can be monitored using the changes observed on its dynamical behavior. In this paper, artificial neural networks are used to estimate the depth of the dynamical water level of groundwater wells in relation to water flow, operation time and rest time. Simulation results are presented to demonstrate the validity of the proposed approach. These results have shown that artificial neural networks can be effectively used for the identification and estimation of parameters related to systems of water distribution.

Stable isotopes (H-2, O-18 and C-13) in groundwaters from the northwestern portion of the Guarani Aquifer System (Brazil)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Radon in groundwaters from Guarany aquifer, South America: environmental and exploration implications

Groundwater and sandstone samples were analyzed for radon in Guarany aquifer, Parana sedimentary basin, South America. The dissolved radon ranged between 3 and 3303 pCi/l, being lognormally distributed, with a modal value of 1315 pCi/l, and a median value of 330 pCi/l. Rn-222 leakage experiments for sandstones yielded a theoretical value of 1390 pCi/l for Rn-222 in water, showing that theoretical modeling can reliably be used to interpret laboratory and field data. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

A combined method for evaluating radon and progeny in waters and its use at Guarani aquifer, São Paulo State, Brazil

A combined method for evaluating radon (Rn-222) and progeny (Pb-214 and Bi-214) in water was developed by using inexpensive alpha scintillation Counting and gamma ray spectrometry through NaI(Tl) scintillation detectors. A groundwater sample collected at the Pocos de Caldas alkaline massif in Brazil was submitted to the technique in order to assure its applicability by comparing the volumetric activities by different methods. Similar volumetric activity was determined for Pb-214 and Bi-214 in the sample analyzed that is compatible with the expected condition of radioactive equilibrium between these nuclides. The combined method was successfully used to analyze groundwater samples from Guarani aquifer in S (a) over tildeo Paulo State, Brazil, and the results of the measurements indicated that Pb-214 and Bi-214 provide useful information concerning the evaluation of the drinking water quality in terms of radiological aspects. This is because they are directly identified in the water samples, without the need of requiring the assumption of the establishment of the transient equilibrium condition with its parent Rn-222. (c) 2005 Elsevier Ltd. All rights reserved.

Hydro(radio)chemical relationships in the giant Guarani aquifer, Brazil

This investigation was carried out within the Parana sedimentary basin and involved the sampling of 78 pumped tubular wells for evaluating the hydrochemistry and radioactivity due to the nuclides (238)U, (234)U, (222)Ra, (226)Ra, and (228)Ra in the Brazilian part of Guarani aquifer. Several significant correlations were found involving the geostatic pressure, for instance, specific flow rate, CO(3)(2-), SO(4)(2-) temperature, dissolved O(2), free CO(2), pH, redox potential Eh, conductivity, Na, HCO(3)-, CO(3)(2-) , SI(calcite), Cl(-), F(-), SO(4)(2-), and B. Carbonates precipitation was evidenced by inverse correlation between CO(3)(2-) and Ca, Mg, Sr, and Ba, whereas Na exhibited an opposite trend, dissolving rather than precipitating with increasing CO(3)(2-) concentration. An inverse correlation between 3 and K was found, possibly related to the increasing tendency of K to recombine with the thickness of the clayey layers. HCO(3)-played an important role on Na, Ca, Mg, and Sr dissolution. The dissolved U content and (234)U/(238)U activity ratio data were plotted on a two-dimensional diagram that was successfully utilized on identifying an unreported zone of U accumulation, though not necessarily of economic size and grade. The variability in chemical and radionuclides data indicated an important influence of the underlying Paleozoic sediments in the composition of waters from Guarani aquifer. The available data allowed estimate the groundwater residence time by two U-isotopes disequilibrium methods. Values of 45-61 ka were initially calculated, depending on the adopted porosity (15-20%), but a longer residence time (- 640 ka) was also estimated, which is more compatible with the hydraulic conductivity data in Guarani aquifer and groundwater flow velocity occurring at Milk River aquifer, Alberta, Canada. Such time range agrees with previously reported (14)C ages exceeding 30 ka BP at the more central parts of the Parana sedimentary basin. (c) 2005 Elsevier B.V. All rights reserved.

Some possible evolutionary scenarios suggested by Cl-36 measurements in Guarani aquifer groundwaters

The Guarani aquifer underlies 1.2 M km(2) in the Parana sedimentary basin of South America and is an important source of water for industry, agriculture, and domestic supplies. To determine the sustainability of this aquifer we need to understand the dynamics of the groundwater system. This paper describes the first Cl-36 measurements on aquifer groundwaters and some measurements on South American rainwaters, thought to be indicative of the recharge water. The results are compared to previous work in the region, including other radioisotope analyses. A simple model is developed, incorporating radioactive decay, allowing scenarios to be developed for mixing different waters at different mixing rates. Thus, mixing scenarios consistent with other hydrogeological and hydrogeochemical data could be assessed. A model that mixes fresh recharging waters with formational waters, that contain elevated chloride levels, but low (in situ) Cl-36 levels, can explain most of the results presented here. The expectation that rainwater samples would provide a good end-member for modelling recharge proved problematic, however. As a consequence, it is suggested that either: the recharge waters are not sourced from the same locations as the rains; that the current rainfall and fallout conditions were significantly different in the past; or that the low levels of chloride in rainfall may have allowed some contamination of the samples by old (Cl-36-free) chloride during the recharge process. (c) 2008 Elsevier Ltd. All rights reserved.

Dissolved Po-210 and Pb-210 in Guarani aquifer groundwater, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development of environmental and natural vulnerability maps for Brazilian coastal at Sao Sebastiao in São Paulo State

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)