Repositório da Universidade dos Açores
Repositório Institucional da Universidade dos Açores
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Hydrogeophysics and Hydrogeology of volcanic islands, characterization of aquifers in the Azores
Publication . Borges, Paulo Filipe Silva; Rodrigues, Francisco Cota; Befus, Kevin Martin; Cruz, José Virgílio de Matos Figueira
ABSTRACT: Freshwater availability on small volcanic islands is increasingly threatened by human activities and climate change, underscoring the necessity for a deeper understanding of local hydrogeological systems to ensure sustainable water management. This study investigates the hydrogeology and water quality dynamics of two perched aquifers, one on Terceira and the other on Graciosa, two of the islands in the Azores archipelago (Portugal), employing a multidisciplinary approach that integrates geological, geophysical, and hydrochemical tools.
On Terceira Island, the São Sebastião depression hosts a perched aquifer system characterized by significant spatial and temporal variations in groundwater quality. Monthly groundwater sampling from hand-dug wells revealed fluctuations in electrical conductivity (EC), pH, temperature, and chloride (Cl⁻) content. Statistical methods, including cluster and principal component analysis (PCA), were applied alongside hydrochemical and geophysical approaches. The results indicated substantial spatial variability in groundwater quality related to cesspools, agriculture, and other human activities. Temporal analysis highlighted seasonal variations in groundwater temperature and pH, influenced by shallow water table dynamics and agricultural practices. The relationship between EC and Cl- content, along with nutrient analysis, suggests that septic systems and agricultural runoff contribute to groundwater contamination. The findings underscore the need for targeted groundwater management strategies, including enhanced monitoring, stricter regulation of agricultural practices, and the development of sustainable land and water management practices to ensure safe and adequate water resources for the future. Geophysical investigations were carried out using electrical resistivity technique (ERT) surveys, which provided insights into the spatial distribution of geological saturated layers, suggesting continuity of the aquifer and potential for productivity.
On Graciosa Island, which has the lowest average annual precipitation in the Azores (≈920 mm), groundwater faces complex issues related to saltwater intrusion, necessitating new solutions and management strategies. A conceptual hydrogeological model was developed based on published data, primarily about geology and hydrochemistry, along with field data. This model identifies a basal aquifer as the island's primary water source and some perched aquifers linked to springs and hand-dug wells. Groundwater recharge is mainly associated with direct infiltration of rainwater into the island’s surface, rapidly reaching the perched aquifers. Discharge inland occurs through springs and drilled wells. Over-exploitation of boreholes is contributing to the salinization of the basal aquifer, highlighting the need for improved water abstraction strategies. The occurrence, circulation, and storage of groundwater within the Graciosa volcanic structure are represented here through a hydrogeological conceptual model.
Further investigation of the perched aquifer on Graciosa Island revealed its potential as an alternative freshwater resource. Hydrochemical analysis, hydrostatic level measurements, and electrical resistivity tomography (ERT) confirmed the presence of a new perched aquifer in Guadalupe, sharing similarities with other perched aquifers across the Azores. Despite its relatively low mineralization, groundwater quality is compromised by high nitrate concentrations attributed to intensive agricultural activity. Given the increasing risk of saltwater intrusion into the basal aquifer, perched aquifers may serve as a crucial complementary water source to mitigate salinization risk.
This study enhances the understanding of groundwater occurrence, flow, and vulnerability in small island settings by integrating hydrogeophysical techniques with water quality assessments. The results provide critical insights for developing sustainable freshwater management practices, which are essential for ensuring long-term water security for island communities facing increasing climatic and human-induced pressures.
Assessment of volcanic hazards from explosive eruptions on islands: the case of São Miguel (Azores)
Publication . Aguiar, Simone Correia; Pacheco, José Manuel Rodrigues; Pimentel, Adriano Henrique Gonçalves; Sandri, Laura
ABSTRACT: Volcanic islands face unique challenges when impacted by explosive eruptions due to their geographic isolation, small land area, typical rough topography, and proximity of populated areas and infrastructure to volcanic centres. The stratigraphic record of island volcanoes is often incomplete or poorly preserved, generating large uncertainties regarding their past eruptive behaviour, limiting eruption forecasting.
São Miguel Island in the Azores Archipelago is one such case, hosting three active central volcanoes (Sete Cidades, Fogo, and Furnas) that have produced a wide variety of eruptions in the last millennia, ranging from highly explosive trachytic events to basaltic flank eruptions.
This work presents, for the first time in the Azores, a long-term Probabilistic Volcanic Hazard Assessment (PVHA) using São Miguel Island as a case study. The development of this type of analysis requires the integration of different sources of information, including the probability of future eruptions, the probability of opening new vents, and probabilistic numerical simulations of tephra fallout for different eruption scenarios, which are combined into Bayesian Event Trees to generate probability maps, hazard maps, and hazard curves.
Temporal analysis was performed first to estimate inter-event times (IET), i.e., the time intervals between successive eruptive events, using different statistical distributions, and to compute the probabilities of an eruption in the next 50 years for each central volcano. This was achieved by implementing an innovative methodology that focuses on the generation of synthetic catalogues by randomly assigning stratigraphic-consistent ages and accounting for age uncertainties of past events. Catalogues of basaltic (s.l.) and trachytic (s.l.) events (BT catalogues), and catalogues of trachytic (s.l.) events (T catalogues) were generated for each of the three central volcanoes.
The results revealed that Sete Cidades data are non-stationary, suggesting an incomplete eruptive record or changes in eruption frequency over time. The mean IET were shorter for Sete Cidades Volcano (154 yr and 205 yr for BT and T catalogues, respectively) than for Fogo (546 yr for BT catalogues and 909 yr for T catalogues) and Furnas volcanoes (318 yr for T catalogues). The mean probabilities of an eruption within the next 50 years are higher for Sete Cidades (21% for BT and 17% for T catalogues), followed by Furnas (13% for T catalogues), and Fogo (8% for BT and 5% for T catalogues).
Spatial analysis was performed separately for each central volcano to identify areas with a higher probability of hosting future eruptive centres. This was accomplished by implementing the kernel method and using the location of past vents, either central vents or eruptive fissures. Different datasets were considered for this analysis: basaltic (s.l.) and trachytic (s.l.) centres together, including fissures and central vents (BT datasets), trachytic (s.l.) vents of explosive and effusive events (T datasets), and only explosive trachytic (s.l.) vents (ET datasets).
Different kernel functions (Gaussian, Cauchy, Exponential, and Uniform) were explored and the best degree of clustering of eruptive centres (given by a smoothing parameter h) was determined for each dataset of each volcano. Vent opening probability maps (susceptibility maps) were computed by combining the pair (kernel function and smoothing parameter) that best described the empirical cumulative distribution function of the distance between eruptive centres. The results show that for the Sete Cidades BT dataset, the most likely locations to host future vents are located on the southeast flank (30%), the caldera (17%), and on the southwest flank (8.7%). However, when considering future trachytic (s.l.) vents, higher probabilities were obtained for the caldera (51%) and the southwest sector (28%). Explosive trachytic (s.l.) eruptions are more likely to occur only inside the caldera (83%). On what concerns Fogo Volcano, the most likely locations to host future eruptive centres (BT dataset) include the west-northwest flank (29%), the caldera (9.6%), and the southwest flank (6%). Regarding future trachytic (s.l.) events, the most probable locations to host new vents are the west-northwest flank (25%), the caldera (17%), and the north-northeast flank (15%). Explosive trachytic (s.l.) eruptions are more likely to occur inside the caldera (29%) and on the north flank (9.3%). For Furnas Volcano, the most probable locations to host future eruptive centres (BT dataset) are inside the caldera complex (34%), on the northern flank (31%), and on the eastern flank (15%). Regarding the opening of future trachytic (s.l.) vents, the most likely locations are the interior of the caldera complex (63%) and on the north flank (21%). In the case of explosive trachytic (s.l.) eruptions, future vents are highly probable inside the caldera complex (91%).
A long-term PVHA framework, rooted on Bayesian inference, was applied to each central volcano, focusing on explosive trachytic (s.l.) eruptions to evaluate the impact of tephra load on São Miguel Island over the next 50 years (absolute probabilities) and conditional to the occurrence of a future VEI 4 eruption (conditional probabilities).
The computed absolute probability maps indicate a higher probability of exceeding lower tephra load thresholds (e.g. 1 and 10 kg/m2) in the next 50 years compared to higher accumulations of tephra (e.g. 400 kg/m2), with Sete Cidades and Furnas volcanoes being the main contributors to exceeding these tephra loads.
The obtained hazard maps indicate that tephra loads between 200 kg/m2 and 300 kg/m2 and between 50 kg/m2 and 200 kg/m2 (thicknesses of 20 to 30 cm and 5 to 20 cm) are expected at locations close to Sete Cidades and Furnas, respectively, suggesting that these volcanoes represent a greater threat to local populations over the next 50 years.
The hazard curves computed for critical infrastructures such as the Ponta Delgada airport, Divino Espírito Santo hospital, and Pico Vermelho geothermal powerplant reveal that Sete Cidades Volcano represents the greatest threat to the airport and the hospital, while Fogo Volcano has the greatest impact on the geothermal powerplant within the next 50 years.
Combining the results of the PVHA for each volcano revealed that the area between Relva and Caloura parishes, in the southern part of São Miguel, and the area of Nordeste parish, are less vulnerable to tephra fallout in the next 50 years.
Key determinants of customer satisfaction in tourism and hospitality
Publication . Farinha, Carlos Filipe da Silva Ferreira; Tiago, Maria Teresa Pinheiro de Melo Borges; Avelar, Sónia Margarida Moreira
Esta investigação analisa o impacto da combinação entre inovação e sustentabilidade na satisfação dos clientes no turismo, uma indústria em constante transformação. Estudos anteriores tendem a considerar estes fatores de forma isolada. Assim, recorreu-se a uma investigação multi-métodos, composta por quatro estudos: uma análise bibliométrica, entrevistas a gestores do setor, um estudo de métodos mistos com turistas e um inquérito quantitativo em duas fases dirigido a hóspedes de hotéis. Os resultados destes estudos demonstram que tanto a inovação como as iniciativas de sustentabilidade podem potenciar a satisfação, sobretudo se implementadas em conjunto e de forma alinhada com as preferências dos clientes. Este impacto é mais expressivo através da melhoraria da perceção de qualidade, um mediador central que traduz a inovação e a sustentabilidade em maior satisfação. Nem todas as inovações são valorizadas da mesma forma: melhorias diretamente experienciadas pelos clientes têm um impacto mais forte na qualidade percebida e na satisfação, comparativamente a alterações não visíveis. Além disso, inovar sem ter em consideração as necessidades dos clientes pode ter efeitos indesejados, ao gerar frustração. A análise identificou ainda segmentos distintos de turistas com diferentes preferências como os “entusiastas da inovação”, mais recetivos a ofertas tecnológicas e sustentáveis, que contrastam com os “fiéis à qualidade”, que privilegiam consistência e mostram maior resistência a mudanças disruptivas. Estes resultados evidenciam a necessidade de adaptar as estratégias de inovação e sustentabilidade aos perfis e expetativas dos clientes, em vez de optar por soluções indiferenciadas. Ao propor um quadro conceptual integrador que articula a inovação com medidas sustentáveis, esta investigação demonstra que o alinhamento de novas ofertas com as preferências e o contexto dos clientes gera melhorias mais expressivas na sua satisfação. Ao mesmo tempo, a melhoria da satisfação conduz a resultados comportamentais desejáveis, como maior fidelização, recomendações positivas e uma maior disposição para pagar mais. Do ponto de vista prático, a investigação evidencia que as empresas no setor do turismo e hotelaria podem desenvolver uma vantagem competitiva ao combinar a inovação em serviços com iniciativas de sustentabilidade, alinhadas com as preferências dos segmentos-alvo.
O impacto económico da Covid-19 nas Microentidades da Região Autónoma da Madeira
Publication . Silva, Alison Michel Ramos da; Batista, Maria da Graça Câmara; Sousa, Áurea Sandra Toledo de; Fernandes, Paulo Filipe
Com características próprias de uma região insular e ultraperiférica, a economia da Região Autónoma da Madeira (RAM) depende fortemente do setor do turismo, tendo sido particularmente afetada pela pandemia da COVID-19. Considerando o peso das microentidades no tecido económico regional, totalizando 96% das empresas e quase metade dos postos de trabalho do setor privado na Região, este estudo teve como objetivo avaliar o impacto económico da pandemia nas microentidades com sede na RAM e analisar as respetivas estratégias de gestão e acesso aos apoios públicos.
Recorrendo a uma metodologia mista, que combinou análise documental, inquérito por questionário e entrevistas semiestruturadas, foi possível caracterizar os principais constrangimentos enfrentados, a eficácia das medidas de mitigação nacionais e regionais, e o papel da literacia financeira na capacidade de adaptação e tomada de decisão dos microempresários.
Os resultados revelam um impacto económico transversal, mitigado por medidas públicas percecionadas como eficazes, apesar de barreiras no acesso. A maioria dos empresários expressou satisfação com os apoios recebidos, sobretudo pela preservação dos postos de trabalho. Verificou-se ainda um processo de recuperação económica acelerado, favorecido pela retoma do turismo, mas sem mudança estrutural significativa nos modelos de gestão, condicionada por resistência à mudança, dependência continuada dos apoios públicos e níveis baixos de literacia financeira e digital.
Estes resultados permitem identificar pistas para o reforço da resiliência das microentidades, destacando a importância da capacitação técnica, da simplificação administrativa e da modernização dos processos de gestão.
PRISMAC – Análise, mitigação e gestão do risco de movimentos de vertente potenciados pelas alterações climáticas na Macaronésia.
Publication . Marques, Rui; Silva, Rui; Silva, Maria João
O projeto PRISMAC – Análise, Mitigação e Gestão do Risco de Movimentos de Vertente Potenciados pelas Alterações Climáticas na Macaronésia (ref.ª 1/MAC/2/2.4/0112) enquadra-se na necessidade de promover o desenvolvimento sustentável de regiões ultraperiféricas, nas quais fatores meteorológicos adversos, frequentemente agravados pelas alterações climáticas, contribuem para desequilíbrios ambientais e para a ocorrência de catástrofes naturais.