Navegando por Assunto "Groundwater"
Agora exibindo 1 - 7 de 7
- Resultados por Página
- Opções de Ordenação
- An approach to map karst groundwater potentiality in an urban area, Sete Lagoas, Brazil(2020-09-28) Magnabosco, Rafael; Galvão, Paulo; de Carvalho, Ana MacielDue to complex hydrogeological contexts, mapping groundwater potential zones in karst regions is a difficult task. This study was conducted on a karst terrain in Sete Lagoas, Brazil, where rapid urban growth without adequate water resources management resulted in the drilling of unproductive wells and possible aquifer over-exploitation due to the concentration of wells. The objective was to develop a method for mapping groundwater potentiality for karst aquifers, serving as water resources management tool, based on 3D geological modelling, field work and pumping test data, remote sensing, geophysics analysis and production of thematic maps, resulting in the hydrogeological conceptual model. The groundwater potentiality map showed that most potential zones are on the central area, limited by grabens, where limestones are in contact with unconsolidated sediments, on areas with higher density of morphostructural and geophysical lineaments, mainly in east–west and north–east directions, near karst surface features, on thicker karstified zones, with higher recharge rates.
Item Análise de suscetibilidade à eventos cárstico-geotécnicos em região centro-urbana do município de Sete Lagoas-MG(2023) Oliveira, Júlia Moura de; Schuch, Camila S.; Galvão, Paulo Henrique FerreiraEm regiões cársticas podem ocorrer diversos problemas atrelados à superexplotação de água subterrânea, sendo um deles os abatimentos de solo, fenômeno que pode estar relacionado à dissolução de rochas carbonáticas. A cidade de Sete Lagoas (MG) teve seu primeiro grande abatimento registrado em 1988 e, a partir daí, houve novas ocorrências ao longo dos anos. Este trabalho fundamenta-se na investigação da evolução da suscetibilidade cárstica-geotécnica em Sete Lagoas, entre as décadas de 1940 a 2020, bem como na análise acerca da ocupação do espaço urbano nesse período. A análise foi realizada por meio da elaboração de mapas de suscetibilidade em intervalos de 20 anos, ponderando fatores de predisposição geológica e hidrogeológica locais. A partir da soma desses fatores, obteve-se o mapa final denominado risco cárstico-geotécnico. Por meio da reclassificação dos valores, definiu-se diferentes níveis de risco na área, em uma escala de 0 (zero) a 10, que vão de baixo a alto risco. Com a elaboração desses mapas, pode-se analisar que a suscetibilidade cárstica-geotécnica vem evoluindo, sendo a região associada ao alto risco cada vez maior na área estudada. Se tratando exclusivamente do alto risco cárstico geotécnico, observou-se que nos últimos 20 anos de análise tem-se que a área associada aproximadamente dobrou de dimensão. Além disso, desde seu aparecimento em 1980, houve um crescimento de aproximadamente 2800% em sua área até o ano de 2020. Outra constatação foi de que a explotação de água subterrânea sem um planejamento adequado, durante um longo período, influencia diretamente na evolução desse risco devido à concentração de poços em pequenas áreas. O agrupamento de poços na área urbana do município gera a sobreposição dos cones de rebaixamento, diminuindo ainda mais os níveis de água subterrânea. Esse fato torna o fator hidrogeológico o mais influente no mapa cárstico geotécnico quando comparado ao fator geológico, sendo que o risco ligado à hidrogeologia se altera significativamente no período de tempo analisado. Desde o aparecimento da zona de alto risco cárstico geotécnico, em 1980, essa área está integralmente dentro da mancha urbana relativa as décadas analisadas. Os pontos de abatimentos também estão em sua totalidade dentro das manchas urbanas referentes aos anos de 2000 e 2020. Conclui-se que suscetibilidade cárstica geotécnico está evoluindo no decorrer do tempo. Pode-se perceber também a influência direta da explotação de água subterrânea sem gerenciamento adequado na evolução desse problema, podendo influenciar na ocorrência dos abatimentos na área urbana de Sete Lagoas, principalmente em regiões onde se tem alta concentração de poços.Item First Steps to understanding Intrinsic Vulnerability to Contamination of Karst Aquifers in Various South American and Caribbean Countries(2023) Souza, Rogério Tadeu de; Travassos, Luiz Eduardo Panisset; Heredia, Olga Susana; Paparas, Mariana Alicia; Sicilia, Silvia Alejandra; Patat, Franco Urbani; Ortega, Rosa María Valcarce; Rodríguez, Moraima Fernández; Corrales, Liane Gamboa; Enríquez, Nathalia Vanessa Uasapud; Duarte, Yameli G. Aguilar; Bautista, FranciscoProtecting groundwater in karst aquifers is extremely important. Vulnerability maps can greatly help proper decision making based on physical environmental attributes that influence how easily a contaminant applied to the land surface can reach groundwater due to anthropogenic activities, and the properties of the contaminants. Methods for determining vulnerability based on the COST Action 620 Approach, when applied in the study area, may lead to contradictory results. The main purpose of this study is to provide an overview of academic research on intrinsic karst aquifer vulnerability methodologies applied in South American and Caribbean countries. Secondly, it describes studies related to karst aquifers that, in some cases, lack specific information on intrinsic vulnerability. The objective is to encourage and to help develop specific methods for determining karst vulnerability in these regions. To achieve these purposes, a systematic literature review was conducted including studies conducted at institutions such as universities, national water institutes, and by geological services. Several methods have been used in the region such as COP, DRASTIC, RISK, EPIK, PI, PaPRIka, and the Slovene Approach. And some attempts have been made to develop a specific methodology that best suits the specificities of the region’s karst aquifers. South America and the Caribbean have almost 5 % of the world´s carbonate rocks. Some countries have large extensions of their territory covered by karst rocks, such as Peru, 15.4 %; Cuba, 67 %; and Mexico 25.29 %. Estimates indicate that more than 10 million people use water from karst systems in Mexico. In Cuba, 33 % of all available water volume originates from groundwater, and 91.51 % from karst aquifers. In Mexico, 13 studies have been conducted on the importance of karst aquifers, which mostly address the Yucatan Peninsula, followed by Brazil (9 studies), Cuba (5), Colombia (1) and Peru (1). Information about the theme is scarce in most of the other countries in the region. Some studies have incongruent results given the regional characteristics of tropical karst.- Geological and hydrogeological review of a semi-arid region with conflicts to water availability (southeastern Brazil)(2021-11) P.Bhering, Apolo; Antunes, I.M.H.R.; A.G.Marques, EduardoGroundwater consumption has become increasingly relevant for urban development. The city of Montes Claros (Minas Gerais, Brazil) is located in the border region of the Brazilian semi-arid polygon and has registered conflicts of water use for decades ago. The study area contains a complex karst system responsible for the heterogeneous permeability of water recharge and groundwater flow. The urban area of Montes Claros is located in the Vieira River watershed and contains different groundwater wells used to agro-industrial and human consumption. Almost groundwater captions have a low specific capacity with a consequent groundwater depletion. On the region, there are significant areas with a negative water balance concerning to water recharge and groundwater exploitation. Groundwater flow has a regional dominant direction of SW-NE, however locally, groundwater flow varies and could be identified some clusters with high hydrological potential. The contrast between hydrogeological features of the outcropping lithotypes added to the geological structures contribute to variations in the potentiometric level and in the productivity of aquifers. The main aim of this study is a reviewer of the regional hydrogeology of the municipality of Montes Claros to evaluate a potential groundwater availability on the urban area and minimize a groundwater overexploitation and scarcity. A detailed characterization of the local hydrogeology from Montes Claros region will be crucial to a definition of more efficient water supply policies on the management of water resources, particularly in a scenario of climate change and water scarcity in semi-arid areas.
Item Hydrogeology of Karst and Metapelitic Domains of the Semi-Arid Vieira River Watershed (Brazil)—A Contribution to Groundwater Resource Management(2023-05-29) Bhering, Apolo Pedrosa; Antunes, Isabel Margarida Horta Ribeiro; Marques, Eduardo Antonio Gomes; Paula, Rodrigo Sergio de; Silva, Antônio Roberto NunesWater scarcity is a problem in Brazil’s northern semi-arid domain. Montes Claros is the most populated Minas Gerais city in this context, and its socio-economic problems are related to water consumption and management. Aiming to help assess these problems, this study presents a new hydrogeological characterization. The 3D geological model was developed using drilling data from 125 public wells, field campaigns and satellite images for hydrogeological interpretation. The area has two main different aquifer systems underlying the Vieira River Watershed. The first is a karstic fissured aquifer, located in the Lagoa do Jacaré limestone Formation. The second is fissured aquifer systems in metapelites from the Serra da Santa Helena and Serra da Saudade Formations, which are characterized by low hydraulic transmissivity and locally higher specific capacity zones related to their structural features or carbonate intercalations. Monitoring data from new manual and automatic methods carried out in 16 selected points highlight that variations are related to (1) hydrogeological domains, (2) oscillations related to interference from neighboring wells, and (3) seasonal variation and irregular pluviometry in the region. This is important information that can help update our hydrogeological knowledge, provide information on surface and groundwater flow dynamics, and improve water resource management, with the aim of ensuring sustainability in exploitation.- Natural background levels and validation of the assessment of intrinsic vulnerability to the contamination in the Carste Lagoa Santa Protection Unit, Minas Gerais, Brazil(2019-12-21) Aragão, Frederico; Nunes Menegasse Velásquez, Leila; Galvão, Paulo; de Castro Tayer, Thiaggo; Nogueira Lucon, Thiago; Ruchkys de Azevedo, ÚrsulaThe contamination of karst aquifers by anthropogenic activities causes a major issue regarding environmental policies, since they present high sensitivity, influenced by unique features such as dolines, swallow holes, and conduits. This paper is focused on the Carste Lagoa Santa Protection Unit, MG, Brazil, and presents three main objectives: to determine the natural background levels of chloride, nitrate, sulfate, and phosphate; to indicate the locations where the concentrations of those parameters exceed the natural background levels in the existing vulnerability map and, finally, to determine the proportion of the areas (in percentage) where this surpassing occurs, according to the vulnerability classes (high, moderate and low). Results have shown values (90th percentile) of 2.4 mg/L, 1.0 mg/L, 5.3 mg/L, and 0.1 mg/L, for Cl−, NO3−, SO4−2, and PO4−3, respectively, indicating that for all four parameters, there were areas (mainly distributed within moderate vulnerability portions) where the values were surpassed, which suggests anthropogenic activity due to the presence of urban settlements and agricultural activities. Therefore, the proposal of natural background levels was essential to understand the hydrochemistry of the studied region.
Item Natural responses of Neoproterozoic dynamic karst springs to rainfall events, São Miguel Watershed, Minas Gerais, Brazil(2024-03-03) Marques, Tássia; Galvão, Paulo; Assunção, Pedro; Pandolf, Bruno; Marshall, Peter; Paiva, IsabelKarst aquifers consist of complex networks of conduits in which groundwater flows and recharge/discharge processes are generally more dynamic than in other types of aquifers. Due to their intrinsic heterogeneity and anisotropy, monitoring, quantifying, and analysing natural responses of karst springs is an efficient tool. Unlike Cenozoic and Mesozoic rocks, in Neoproterozoic karst systems, groundwater circulates and stores generally in dissolution features known as tertiary porosity, as the rock's primary porosity is recrystallized, considered negligible. This article studies the hydrodynamics of a karst portion of the São Miguel River basin, southwest of the state of Minas Gerais, Brazil. The region is predominantly composed of Neoproterozoic carbonate rocks, dating from about 570 to 540 million years ago. During a hydrological year (2019–2020), three karst springs (S1, S2, and S3) were daily monitored through their natural responses (variations of electrical conductivity, EC, temperature, T, and discharge, Q) to rainfall episodes. The data were interpreted based on the analysis of spring hydrographs, time series, recession curves (seasonal and intra-annual), and statistics of EC, T, and Q variations. The results show the three springs generally exhibit quick flow, typically karstic, in the case of hydrosystems with a well-structured and functional underground drainage network. The time series indicate the hydrosystem drained by S1 presents slower circulation and a lower degree of linearity, resulting from the higher sinuosity of the system, while the hydrosystems of S2 and S3 have similar behaviours, of quick water circulations immediately after a rainy episode. The degrees of karstification classify S1 and S2 as complex and extensive karst systems consisting of several subsystems, and S3 as a system in which the conduit network is more developed at the upper epiphreatic zone than near the outlet.