Modelo matemático de fluxo e transporte de massa do sistema multiaquífero Cretácio da região de Aveiro (Portugal)

Doutoramento em GeociênciasDesde meados da década de 1960, que o sistema multiaquífero Cretácico de Aveiro é intensamente explorado, o que conduziu gradualmente a uma acentuada depressão dos níveis piezométricos regionais. Este facto, porque tem lugar num aquífero costeiro e com uma limitada recarga natural, contribui para aumentar o risco de deterioração da qualidade da água subterrânea, quer por fenómenos de intrusão marinha, quer por mistura com águas de níveis aquíferos profundos com elevado grau de mineralização. Constituindo um recurso de água vital para toda a região, este sistema aquífero adquire um claro valor económico, que exige a adequada avaliação, exploração, gestão e conservação dos seus recursos. A tese Modelo matemático de fluxo e transporte de massa do sistema multiaquífero Cretácico da região de Aveiro (Portugal) representa nesse sentido um esforço sistemático para reunir e integrar toda a informação geológica, hidrogeológica, geoquímica e paleoclimática disponível sobre este sistema aquífero à escala regional, de modo a analisar e desenvolver um conhecimento mais completo do sistema, que permita criar condições para uma exploração sustentável dos seus recursos. Para isso procedeu-se à construção de um modelo tridimensional de diferenças finitas (MODFLOW) a partir de um modelo conceptual e à sua calibração e utilização para descrever o fluxo subterrâneo no aquífero Cretácico de Aveiro. O programa MODPATH foi usado para determinar e ilustrar as linhas de fluxo advectivo regional subterrâneo. O desenvolvimento de um modelo de fluxo e transporte de massa permitiu assim desenvolver um melhor conhecimento do sistema hidrogeológico no seu estado natural e avaliar o impacte ambiental resultante das actividades antrópicas. Permitiu ainda descrever: (1) os limites físicos e hidráulicos do sistema aquífero, e (2) as relações entre as águas superficiais e subterrâneas; (3) criar um modelo numérico que calcule o balanço de água subterrânea, a recarga natural ao sistema, as zonas de descarga e descrever a distribuição de fluxo regional; (4) relacionar o quimismo das águas subterrâneas com as principais direcções de fluxo subterrâneo, e (5) fazer uma previsão dos efeitos à escala regional de uma possível variação na recarga ou na bombagem do aquífero. Os dados geoquímicos foram usados para descrever as relações existentes entre o quimismo da água subterrânea, a mineralogia do aquífero e as principais direcções de fluxo subterrâneo actual e no passado. A variabilidade espacial nas concentrações dos principais solutos foi avaliada e relacionada com a variação das propriedades do aquífero à escala regional. As análises químicas e isotópicas da água subterrânea e do próprio material aquífero ao longo das principais direcções de fluxo foram usadas para avaliar os processos hidrogeológicos e geoquímicos predominantes no aquífero e para fazer a datação das águas subterrâneas.The Aveiro Cretaceous aquifer has been exploited for public and industrial supply since the nineteen sixties. Groundwater intensive exploitation is affecting the natural piezometric surface and threatening the balance of this natural system. In recent years, a continuous fall in the piezometric surface has been observed due to intensive groundwater abstraction leading in some areas to values of -25 m below mean sea level. Because it occurs in a coastal aquifer, partially confined and with limited natural recharge, there is the threat of it leading to gradual deterioration of the water quality, either because of saltwater intrusion or due to mixing with very high-mineralised waters from deeper aquifer levels, nowadays with higher water potentials. This aquifer has proven to be quite unique in Europe from the geochemical point of view. It is very important as an archive of past climate conditions in temperate regions of Europe and is nowadays recognised as a strategic water resource for the Aveiro region. It has clear economic importance requiring an adequate evaluation, exploitation, management and preservation of its resources. The thesis ‘Flow and transport model of the Aveiro Cretaceous multilayer aquifer (Portugal)’ represents a systematic effort to assemble geologic, hydrologic, and geochemical information, to analyse and develop an understanding of the system, and to develop predictive capabilities that will contribute to an effective sustainable management of the system. The approach followed required the construction of a three-dimensional finite difference groundwater flow model (MODFLOW), and its calibration and use to describe the regional flow. The particle-tracking program MODPATH was used to determine and illustrate simulated advective regional groundwater flow patterns. The use of computer simulation contributed to develop an understanding of the natural, undisturbed hydrologic system and the changes brought about in it by human activities. It also contributed to describe: (1) the physical and hydraulic boundaries of the aquifer system, and (2) the regional relations between surface water and groundwater; (3) to devise a numerical model to compute a regional groundwater budget, regional recharge and discharge areas and the patterns of regional groundwater flow; (4) to relate groundwater chemistry to these patterns of regional flow; and (5) to predict the effect of a possible variation in the recharge or volume of abstraction on a regional scale. Geochemistry data were used to describe the relations between groundwater chemistry, aquifer mineralogy, and present and past patterns of regional flow. The spatial variability in the concentrations of major solutes in groundwater was evaluated and related to aquifer properties at regional scale. Chemical and isotopic analyses of groundwater and aquifer material along with general directions of regional groundwater flow were used to evaluate the important hydrological and geochemical processes controlling groundwater chemistry and to estimate groundwater ages qualitatively

XXXV Congress of the International Association of Hydrogeologists, Groundwater and Ecosystems – Abstract Book

Resumos das comunicações do XXXV Congresso da Associação Internacional de Hidrogeólogos (IAH

Reservas estratégicas de água subterrânea na Região Centro (Projecto Images)

Comunicação apresentada em Powerpoint, composta por 12 slide

Spatial patterns of surface water quality in the Cértima River basin, central Portugal

The Cértima River is the principal source of water flowing into the Pateira de Fermentelos, which is one of the largest natural lakes of the Iberian Peninsula and has elevated conservation value. This study aims at a more comprehensive understanding of the spatial pattern in water quality and, thus, pollution problems in and especially upstream of the Pateira, including a comparison with a prior study in 2003. To this end, surface water samples were collected, in May 2007, at 29 sites covering the basin's four main types of water bodies, and analysed for electrical conductivity, dissolved oxygen, biochemical oxygen demand, total suspended solids, various nitrogen species, orthophosphate and chlorophyll a. The results confirmed the existence of marked pollution along the middle section of the Cértima's main course, which can be attributed to wastewater discharges of urban and animal husbandry origin in particular. This represents an important eutrophication risk to the Pateira. Current legislation and water management does not appear to tackle this risk in an entirely satisfactory manner, since the spatial patterns as well as actual values of key physic-chemical parameters do not appear to have changed markedly between 2003 and 2007. Amongst the various parameters, biochemical oxygen demand stands out for frequently exceeding the legal water quality standards. The type of water body proved helpful to explain part of the variation in some of the parameters. This includes clear differences in electrical conductivity between the right- and left-bank tributaries, illustrating well the heterogeneous and complex character of the Cértima basin.publishe

Thermal-Based Remote Sensing Solution for Identifying Coastal Zones with Potential Groundwater Discharge

Submarine Groundwater Discharge (SGD) is an essential process of the hydrological cycle by hydraulically connecting the land and sea. However, the occurrence, importance and effects of SGD remain largely underexplored. Here, we developed and validated a straightforward tool for mapping potential SGD areas in coastal ecosystems of Portugal. Our approach was based on the premise that relatively cooler groundwater discharging to warmer coastal waters manifests in the thermal band of satellite imagery acquired during the summer months. We then used Landsat 8 thermal infrared imagery (TIR) to derive sea surface temperature and standardized temperature anomalies maps. The results confirmed the capacity of TIR remote sensing for identifying SGD areas. The thermal analysis enabled us to acquire a useful visual-spatial correlation between the location of thermal anomalies and potentiometric surfaces of coastal aquifers. This way, over 20 potential SGD areas were identified. Our study makes an important contribute to our current SGD research status by developing a cost-efficient tool which can be used as a first level approach for large areas. Further investigation is needed to quantify the SGD and its potential effect in the receiving ecosystems, especially those located within environmentally protected areas

Groundwater and Ecosystems

Scientific contributions in 24 chapters of authors of different parts of the World, with great diversity of areas and investigation topics on the important temathic of groundwater and its dependent ecosystems

Human predisposition to cognitive impairment and its relation with environmental exposure to potentially toxic elements

International audienc

Submarine FREsh water dischargEs: characteriZation and Evaluation (Projecto FREEZE)

ABSTRACT: The flow of terrestrial groundwater towards the sea is an important natural component of the hydrological cycle (Church, 1996). Hydrological studies have shown that land derived fresh groundwater may discharge through the sea floor through a process known as submarine groundwater discharge (SGD, Taniguchi et al., 2002). Many studies have highlighted the ubiquitous occurrence on the near-shore environment (Bratton, 2004) and for carbonate acquiferous (limestones or dolomite) with dissolution flow conduits discharge in the form of submarine freshwater springs is a well-known phenomenon (Moore, 2008; Taniguchi et al., 2002). In Portugal, groundwater supplies about 70% of the fresh water needs and most of the aquifers are hosted in sandstones and limestones along the Portuguese coastline where more than 60% of the whole population dwells. It is assumed in various cases that the aquifers discharge to the sea based on the hydraulic heads, geology and geometry of the aquifers, and on the results of numerical models. The identification and quantification of groundwater submarine discharge is crucial for water and ecosystem management. At present, the over-exploitation observed in the main deep aquifers located in the Beira-Litoral, SetúbalPeninsula and Algarve regions (north, centre and south of Portuguese littoral) led to the prohibition of drilling new boreholes, which limits local investment and economic development. The project FREEZE - Submarine FREsh water dischargEs: characteriZation and Evaluation study on their impact on the Algarve coastal ecosystem (PTDC/MAR/102030/2008) is a Portuguese national research project funded by FCT. The project started officially in January 2010 and was devoted to the study of the freshwater submarine groundwater discharges (SGD's) at sea off Olhos de Água area (Algarve, South Portugal). The project focused part of its activity on mapping an area in the continental shelf where SGDs are known to occur in the intertidal zone and their monitoring; a remote sensing methodology for detection of SGDs in the offshore have been tested leading to shallow water physical oceanographic parameters acquisition. Estimation of freshwater SGD respect to the local groundwater reserves was another key project aim in the scope to evaluate a possible exploitation or to increase attention to the monitoring of present boreholes exploitation in the studied area. In addition particular attention was dedicated to the analysis and monitoring of the submarine ecosystems and biological communities associated to the discovered SGDs. To achieve all these goals a multidisciplinary team of geologists, geophysicists, oceanographers, hydro-geologists, geochemists and biologists has been gathered in the scope to collaborate approaching the same topic by different point of view. Most of the time, the various investigations/activities have been strictly connected one to each other assuring an immediate feedback and helping in this way to the planning of further initiatives.N/