Navegando por Autor "Galvão, Paulo"
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- 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 Hydrodynamic and hydrodispersive behavior of a highly karstified neoproterozoic hydrosystem indicated by tracer tests and modeling approach(2023-04) Assunção, Pedro; Galvão, Paulo; Lucon, Thiago; Doi, Bruno; Fleming, Peter Marshall; Marques, Tássia; Costa, FelipeBrazilian Neoproterozoic carbonate rocks, dating from about 740–590 million years ago, contain the oldest karst-structured terrains on Earth, resulting in groundwater flow pathways in highly heterogeneous and anisotropic conduit networks. Unlike Paleozoic and Mesozoic rocks, in Neoproterozoic karst systems, groundwater circulates and stores practically through dissolution features characterized as tertiary porosity, as the rock’s primary porosity is recrystallized, considered negligible. However, studies using hydrodispersive equilibrium and non-equilibrium models to estimate flow and transport parameters to base the hydrodynamic behavior of these areas are not common. This paper proposes this, by a set of techniques involving dye tracer tests and the analysis of breakthrough tracer curves (BTCs) in a highly karstified Neoproterozoic terrain. For this, three karst springsheds, in the east, west, and south areas of the São Miguel river watershed, in Alto São Francisco karst region, Brazil, were choose and studied with dye tracer tests using Rhodamine WT and Uranine during dry and wet seasons, associated with regional/local (hydro)geological-structural, geomorphological, and speleological data. The results identified spatial and seasonal variations of water flow and transport parameters, recharge and discharge zones, and water dynamic and speleogenetic evolutions. BTCs models showed the karst systems are very dynamic with seasonal variations, and heterogeneities (bypass, loops and stagnant zones) control the variation of flow and transport parameters. The hydrodispersive parameters (mean flow velocity, and longitudinal dispersion coefficient) and coefficients of non-equilibrium models (partition, β, and mass transfer, ω) show a direct dependence on hydrogeological and speleogenetic contexts. Furthermore, the comparison with other karst systems around the world showed that Neoproterozoic karst has a more stable hydrodynamic behavior under hydrological conditions.Item Karst Hydrological Connections of Lakes and Neoproterozoic Hydrogeological System between the Years 1985–2020, Lagoa Santa—Minas Gerais, Brazil(2024-09-12) Pacheco Neto, Wallace; Paula, Rodrigo de; Galvão, PauloThis study focuses on a complex Brazilian Neoproterozoic karst (hydro)geological and geomorphological area, consisting of metapelitic–carbonate sedimentary rocks of ~740–590 Ma, forming the largest carbonate sequence in the country. At the center of the area lies the Lagoa Santa Karst Environmental Protection Area (LSKEPA), located near the Minas Gerais’ state capital, Belo Horizonte, and presents a series of lakes associated with the large fluvial system of the Velhas river under the influence, locally, of carbonate rocks. The hydrodynamics of carbonate lakes remain enigmatic, and various factors can influence the behavior of these water bodies. This work analyzed the hydrological behavior of 129 lakes within the LSKEPA to understand potential connections with the main karst aquifer, karst-fissure aquifer, and porous aquifer, as well as their evolution patterns in the physical environment. Pluviometric surveys and satellite image analysis were conducted from 1984 to 2020 to observe how the lakes’ shorelines behaved in response to meteorological variations. The temporal assessment for understanding landscape evolution proves to be an effective tool and provides important information about the interaction between groundwater and surface water. The 129 lakes were grouped into eight classes representing the hydrological connection patterns with the aquifers in the region, with classes defined for perennial lakes: (1) constantly connected, (2) seasonally disconnected, and (3) disconnected; for intermittent lakes: (4) disconnected during the analyzed time interval, (5) seasonally connected, (6) disconnected, (7) extremely disconnected, and (8) intermittent lakes that connected and stopped drying up. The patterns observed in the variation of lakes’ shorelines under the influence of different pluviometric moments showed a positive correlation, especially in dry periods, where these water bodies may be functioning as recharge or discharge zones of the karst aquifer. These inputs and outputs are conditioned to the well-developed karst tertiary porosity, where water flow in the epikarst moves according to the direction of enlarged karstified fractures, rock foliation planes, and lithological contacts. Other factors may condition the hydrological behavior of the lakes, such as rates of evapotranspiration, intensity of rainfall during rainy periods, and excessive exploitation of water.- 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.
- Natural Hydrogeochemical Background Levels in the Carste Lagoa Santa Protection Unit, Minas Gerais, Brazil(2020-11-05) Aragão, Frederico; Velásquez, Leila Nunes Menegasse; Galvão, Paulo; Vieira, Luísa CostaThe identification of hydrogeochemical anomalies in karst water resources represents a crucial step in Brazil’s water management plans. Accelerated urban and industrial development occurs in the region that includes the Carste Lagoa Santa Protection Unit, State of Minas Gerais, which may negatively impact its water quality. This paper establishes Natural Background Levels (NBL) of waters collected from deep tubular wells and springs for Si4+, Ca2+, Mg2+, Na+, K+, HCO3, SO42, Clto understand sources of possible geogenic and anthropogenic anomalies. Areas with surpassed thresholds were compared with geological, hydrogeochemical, and land use data. Every parameter, except for chloride, showed elevated concentrations due to lithologic origin. The NBLs for waters of wells and springs are, respectively, 17.9 and 12.7 mg/L (silica), 97.0 and 91.5 mg/L (calcium), 4.9 and 2.9 mg/L (magnesium), 6.2 and 3.8 mg/L (sodium), 1.0 and 0.3 mg/L (potassium), 285.5 and 254.6 mg/L (bicarbonate), 9.4 and 13.6 mg/L (sulfate). Chloride, analyzed only in groundwater, presented 6.7 mg/L indi-cating a possible influence of upstream urban areas of Lagoa Santa and Pedro Leopoldo municipalities. Volatile and Semivolatile Organic Compounds were also analyzed, but all of them were below the detection limit. This work is important to comprehend the NBL of major elements, reveal geogenic anomalies, and distinguish car-bonate aquifer units from the impure ones.
- Natural Hydrogeochemical Background Levels in the Carste Lagoa Santa Protection Unit, Minas Gerais, Brazil(2021-01) Aragão, Frederico; Velásquez, Leila Nunes Menegasse; Galvão, Paulo; Vieira, Luísa CostaThe identification of hydrogeochemical anomalies in karst water resources represents a crucial step in Brazil's water management plans. Accelerated urban and industrial development occurs in the region that includes the Carste Lagoa Santa Protection Unit, State of Minas Gerais, which may negatively impact its water quality. This paper establishes Natural Background Levels (NBL) of waters collected from deep tubular wells and springs for Si4+, Ca2+, Mg2+, Na+, K+, HCO3−, SO42, Cl− to understand sources of possible geogenic and anthropogenic anomalies. Areas with surpassed thresholds were compared with geological, hydrogeochemical, and land use data. Every parameter, except for chloride, showed elevated concentrations due to lithologic origin. The NBLs for waters of wells and springs are, respectively, 17.9 and 12.7 mg/L (silica), 97.0 and 91.5 mg/L (calcium), 4.9 and 2.9 mg/L (magnesium), 6.2 and 3.8 mg/L (sodium), 1.0 and 0.3 mg/L (potassium), 285.5 and 254.6 mg/L (bicarbonate), 9.4 and 13.6 mg/L (sulfate). Chloride, analyzed only in groundwater, presented 6.7 mg/L indicating a possible influence of upstream urban areas of Lagoa Santa and Pedro Leopoldo municipalities. Volatile and Semivolatile Organic Compounds were also analyzed, but all of them were below the detection limit. This work is important to comprehend the NBL of major elements, reveal geogenic anomalies, and distinguish carbonate aquifer units from the impure ones.
Item Natural Hydrogeochemical Background Levels in the Carste Lagoa Santa Protection Unit, Minas Gerais, Brazil(2021-01) Aragão, Frederico; Velásquez, Leila Nunes Menegasse; Galvão, Paulo; Vieira, Luísa CostaThe identification of hydrogeochemical anomalies in karst water resources represents a crucial step in Brazil's water management plans. Accelerated urban and industrial development occurs in the region that includes the Carste Lagoa Santa Protection Unit, State of Minas Gerais, which may negatively impact its water quality. This paper establishes Natural Background Levels (NBL) of waters collected from deep tubular wells and springs for Si4+, Ca2+, Mg2+, Na+, K+, HCO3-, SO42, Cl- to understand sources of possible geogenic and anthropogenic anomalies. Areas with surpassed thresholds were compared with geological, hydrogeochemical, and land use data. Every parameter, except for chloride, showed elevated concentrations due to lithologic origin. The NBLs for waters of wells and springs are, respectively, 17.9 and 12.7 mg/L (silica), 97.0 and 91.5 mg/L (calcium), 4.9 and 2.9 mg/L (magnesium), 6.2 and 3.8 mg/L (sodium), 1.0 and 0.3 mg/L (potassium), 285.5 and 254.6 mg/L (bicarbonate), 9.4 and 13.6 mg/L (sulfate). Chloride, analyzed only in groundwater, presented 6.7 mg/L indicating a possible influence of upstream urban areas of Lagoa Santa and Pedro Leopoldo municipalities. Volatile and Semivolatile Organic Compounds were also analyzed, but all of them were below the detection limit. This work is important to comprehend the NBL of major elements, reveal geogenic anomalies, and distinguish carbonate aquifer units from the impure ones.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.