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Recursos Hídricos Subterrâneos em Aquíferos Cársicos: Caso de Estudo do Sistema Aquífero de Cesareda
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Orientador(es)
Resumo(s)
A água subterrânea constitui um recurso hídrico estratégico, considerando a vulnerabilidade da
água superficial. Por isso é necessário compreender o funcionamento e a capacidade de armazenamento
dos sistemas aquíferos, para uma gestão sustentável dos recursos hídricos subterrâneos, e sua proteção
quantitativa e qualitativa.
Os sistemas aquíferos cársicos são os mais vulneráveis à contaminação e aqueles que, apesar de
serem drenados por nascentes de grande caudal, são mais sensíveis às variações de recarga, devido à
grande heterogeneidade das propriedades hidráulicas e, normalmente, elevada permeabilidade.
O trabalho de investigação desenvolvido no âmbito desta dissertação teve como objetivo
compreender o funcionamento do sistema aquífero da Cesareda e avaliar os seus recursos hídricos
subterrâneos. Foi realizado trabalho de campo para recolha de amostras de água em furos e nascentes,
ao qual se seguiu a recolha de informação sobre as características climáticas, geológicas e
hidrogeológicas existentes, bem como a consulta de metodologias de avaliação de recarga para avaliação
dos recursos disponíveis.
A avaliação de recargo do sistema foi realizada através de três métodos: Método de Índice de
Potencial de Infiltração (IPI); Índice de Recarga Efetiva (IRef); Método de Balanço Hídrico Mensal de
Thornthwaite (ao nível do solo). Através do IPI obteve-se a infiltração potencial do sistema aquífero
entre 34% e 58%, com média de 53%. O IRef avalia a infiltração de sistemas através de um índice que
varia entre 9,8 e 1, sendo 9,8 alta infiltração e 1 baixa infiltração a nula. A área apresentou valores de
IRef de 9,8 a 6,8 com uma média de 8,25. O método de Balanço Hídrico Mensal de Thornthwaite (ao
nível do solo) apresentou apenas superavit entre outubro e fevereiro.
A vulnerabilidade do sistema foi calculada pelo método de EPIK, demonstrando que 99% da
região se encontra na classe de “muito alta vulnerabilidade” e os restantes 1% dentro da classe “alta
vulnerabilidade”. Segundo a Portaria n.º 336/2019, do Diário da República, ambas as classes deveriam
ser consideradas Reserva Ecológica Nacional (REN).
Groundwater is a strategic water resource, given the vulnerability of the surface water. It is therefore necessary to understand how it functions and the storage capacity of aquifer systems, in order to sustainably manage the groundwater resources and protect them from over-exploitation and contamination. Karst aquifer systems are the most susceptible to contamination and those which, despite being drained by high-flow springs, are more volatile in terms of water quantity, due to the existence of long families of fractures ranging from small closed fractures to huge galleries. The aim of the research carried out as part of this dissertation was to understand how the Cesareda aquifer system works and assess its groundwater resources. Fieldwork was carried out to collect water samples from boreholes and springs, followed by gathering information on the existing climatic, geological and hydrogeological characteristics and consulting recharge assessment methodologies to evaluate the available resources. The system was assessed using three methods: the Infiltration Potential Index (IPI) method; the Effective Recharge Index (IRef); and the soil water balance by Thornthwaite (at the level of the soil). The IPI obtained potential infiltration of the aquifer system between 34% and 58%, with an average of 53%. The IRef assesses the infiltration of systems through an index that varies between 9.8 and 1, with 9.8 being high infiltration and 1 being low to zero infiltration. The area showed IRef values of 9.8 to 6.8, averaging 8.25. The soil water balance by Thornthwaite (at the level of the soil) showed that there was only superavit between October and February. The vulnerability of the system was calculated using the EPIK method, it assessed that 98.5% of the region is in the "very high vulnerability" class and the remaining 1.5% in the "high vulnerability" class. According to Portaria n.º 336/2019, of the Diário da República, both should be considered Reserva Ecológica Nacional (REN).
Groundwater is a strategic water resource, given the vulnerability of the surface water. It is therefore necessary to understand how it functions and the storage capacity of aquifer systems, in order to sustainably manage the groundwater resources and protect them from over-exploitation and contamination. Karst aquifer systems are the most susceptible to contamination and those which, despite being drained by high-flow springs, are more volatile in terms of water quantity, due to the existence of long families of fractures ranging from small closed fractures to huge galleries. The aim of the research carried out as part of this dissertation was to understand how the Cesareda aquifer system works and assess its groundwater resources. Fieldwork was carried out to collect water samples from boreholes and springs, followed by gathering information on the existing climatic, geological and hydrogeological characteristics and consulting recharge assessment methodologies to evaluate the available resources. The system was assessed using three methods: the Infiltration Potential Index (IPI) method; the Effective Recharge Index (IRef); and the soil water balance by Thornthwaite (at the level of the soil). The IPI obtained potential infiltration of the aquifer system between 34% and 58%, with an average of 53%. The IRef assesses the infiltration of systems through an index that varies between 9.8 and 1, with 9.8 being high infiltration and 1 being low to zero infiltration. The area showed IRef values of 9.8 to 6.8, averaging 8.25. The soil water balance by Thornthwaite (at the level of the soil) showed that there was only superavit between October and February. The vulnerability of the system was calculated using the EPIK method, it assessed that 98.5% of the region is in the "very high vulnerability" class and the remaining 1.5% in the "high vulnerability" class. According to Portaria n.º 336/2019, of the Diário da República, both should be considered Reserva Ecológica Nacional (REN).
Descrição
Tese de mestrado, Geologia do Ambiente, Riscos Geológicos e Ordenamento do Território, 2024, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Aquíferos Cársicos Infiltração Vulnerabilidade Recursos hídricos subterrâneos Teses de mestrado - 2024