DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Resultados da Pesquisa
Item Quantification by numerical simulation of the impact of gullies on the water budget of a basement area, southeastern Brazil.(2018) Lima, Péterson Gonçalves de; Bacellar, Luis de Almeida Prado; Drumond, Flávio NasserMany regions of the world are affected by high density of large gullies that can impact on water resources. As these impacts have not been properly evaluated, this study presents a quantification model by numerical simulation of the effect of gullying on the water budget. An active gully of a very eroded region (Bação Complex) was selected and systematically monitored during a hydrological year. The simulation of the gully area by finite element method enabled the quantification of impacts, such as baseflow reduction and groundwater drawdown in the vicinity of this erosional feature. The baseflow reduction, when extrapolated to the whole complex, showed a significant baseflow loss during the dry seasons and an increase of stream flows during the rainy seasons, favouring floods. The numerical simulation results indicate that these modifications are relevant and must be considered when managing aquifers in intensely gullied areas with problems related to water availability.Item The hydrogeologic potential conditioning factors of hydrographic catchments of Upper Velhas River Basin, Southeastern Brazil.(2010) Costa, Fernanda Martineli; Bacellar, Luis de Almeida PradoThe hydrogeologic potential of a drainage catchment represents its capacity of sustainable water production, with good maintenance of the baseflows. In basins of similar shapes and bio-climatic characteristics, the potential will depend on several physical and anthropogenic conditioning factors. The determination of the hydrogeologic potential is a complex procedure, but alternative methods exist, in which hydrologic series are used to determine certain indexes, such as the recession coefficient (a), the specific baseflow (SBF), the baseflow index (BFI), transmissivity and storativity. Aiming at the evaluation of the hydrogeologic potential and its conditioning factors in the Maracuja´ River Basin (southeastern Brazil), ten catchments were selected and monitored. The catchments have distinct geologic and geomorphologic characteristics but are submitted to similar climatic conditions. The hydrogeologic potential is higher in crystalline basement areas, especially where the relief is flat and the regolith is thick; however, it is lower in the areas affected by gullies. The advantages of the hydrologic method, in particular to regions where information is scarce, are that it is easily applied and of low cost, enabling the characterization of the hydrogeologic potential and contributing to the management of water resources.Item Analysis of the influence of gully erosion in the flow pattern of catchment streams, Southeastern Brazil.(2007) Costa, Fernanda Martineli; Bacellar, Luis de Almeida PradoThe baseflow of tributaries to the Velhas River in the northwest region of Ouro Preto County (São Francisco Basin, Brazil) has been declining in the last years, without a simultaneous decrease in the water input. This can only be attributed to badly planned human activities, which result in soil crusting or compaction, erosion, among other types of impact, such as groundwater overexploitation and wetland drainage. Almost all of the study area has been eroded by hundreds of large-size gullies. In order to analyze the influence of erosion in the hydrological behavior of small streams, two similar and contiguous catchments were selected. The only remarkable difference between them is a gully that occupies circa 42% of one of the catchments (“eroded catchment”). Rainfall, flow rates and chemical data were obtained throughout a hydrological year and the results showed that the eroded catchment presented smaller baseflow rates and bigger but short-lived stormflows. This contrasting flow regime is attributed to the gully, which is causing the partial withdraw of the regolith and the exposure of weathered rock. As the regolith has smaller hydraulic conductivities and higher storage coefficients, the exposure of weathered rock on the gully floor explains the odd flow behavior of the eroded catchment. Other studies in the same region confirm the impact caused by the gullies. Thus, the superposition of many gullies can cause decrease of the baseflow and increase of the stormflow. As gullies are very common erosion features in Brazil, they should be much more studied in order to better understand this and other similar types of environmental impact.Item Influência dos fatores geológicos, geomorfológicos e antrópicos da produção de fluxo de base em pequenas bacias hidrográficas na apa Cachoeira das Andorinhas, Ouro Preto (MG).(2014) Monteiro, Josefa Clara Lafuente; Bacellar, Luis de Almeida PradoApesar de sua relevância para a segurança hídrica da região metropolitana de Belo Horizonte a área da Área de Proteção Ambiental Estadual da Cachoeira das Andorinhas (APA/CA) ainda é carente de estudos detalhados quanto à disponibilidade hídrica superficial e subterrânea. Neste trabalho objetivou-se estabelecer a influência da geologia, geomorfologia e uso da Terra no potencial hídrico de pequenas bacias hidrográficas situadas na APA/CA. Foram selecionados três pares de bacias, cada par com condições geológicas e geomorfológicas semelhantes, mas com graus distintos de interferência antrópica. Utilizando-se dados de chuva e vazão, obtidos durante um ano hidrológico (Julho/2006– Julho/2007), estabeleceram-se os regimes pluvio-fluviométricos e determinaramse alguns parâmetros hidrológicos, como o fluxo de base pela técnica smoothed mínima e o coefi ciente de recessão (α) pela técnica matching strip. A análise conjugada destes parâmetros, de índices morfométricos e de dados físico-químicos das águas indicam que as bacias em áreas de relevo mais suave tendem a apresentar menores coeficientes de recessão e maiores volumes de fluxo de base. Portanto, nestas áreas o potencial hídrico é maior, já que a vazão das drenagens se mantém por mais tempo na estação seca. O relevo mais suave, com solo mais espesso e maior tempo de trânsito das águas subterrâneas, também justificam as águas mais redutoras e com maiores condutividades elétricas. Os dados também sugerem que as bacias da área com maiores proporções de florestas tendem a apresentar menores fl uxos de base por conta das maiores taxas de evapotranspiração. Os métodos aplicados se mostraram adequados para caracterizar o regime hídrico de pequenas bacias hidrográfi cas e podem ser importantes para a gestão de recursos hídricos.