Coastal lagoons and their watersheds as GWDE: a case study in the southwest coast of Portugal

The study of groundwater dependent ecosystems opened the opportunity to involve specialists of different areas of knowledge in order to obtain answers for complex interrelations between groundwater and the associated ecosystems. The actual study, carried out in two coastal lagoons of the Portuguese SW coast, showed the high dependency of the marine life and vegetation of the lagoons and associated streams discharging in the lagoons on the fresh water supply of these two lagoons and the high contribution they receive from groundwater in the dry period, which corresponds to more than half of each hydrologic year. Every year, the lagoons are artificially opened to the ocean for a few days to a few weeks, which dramatically changes the inside salinity. The sensitivity of these ecological niches is demonstrated by the strong dependence that some species that are more sensitive to high salinity waters show in relation to the entrance of freshwater resultant from the discharge of the phreatic aquifer of Sines sedimentary Basin. The great biodiversity of these lagoons and its precarious balance is only possible to preserve if the aquifer continue to act as a regulatory factor of the lagoon’s salinity. The equilibrium can be changed in the event of overexploitation of the phreatic aquifer, which is not at risk in the near future. In a scenario of climate change the lagoons will benefit from a slow increase in groundwater contribution, due to the rise of sea level, which will be accompanied by a rise in groundwater levels in the aquifer near the sea.

Influence of different land uses on groundwater quality in southern Portugal

In Alentejo region, southern Portugal, differences in groundwater samples from six groundwater bodies covered with different land uses were analysed based on the monitoring plan of the Alqueva multi-purpose project, created in the sequence of the construction of the Alqueva Dam on the Guadiana River, in South Portugal. For most of the groundwater bodies there is a statistical significant difference between magnesium, sulphate, chloride, and phosphate. All of these ions are strongly correlated with land use management. Groundwater, where land is covered by olive groves, has high levels of electric conductivity, calcium, potassium, sulphate, and phosphate. Dry land crops are correlated with calcium, magnesium, chloride and consequently, electric conductivity, phosphates and sulphate. Vineyards are strongly correlated with high sulphate and phosphate levels. This study clearly shows that different land uses within a certain groundwater body influence the water quality in a different way. Therefore, an appropriate soil management should be adjusted to each situation, taking into account the aquifer matrix and the overlying soil.

Modelo hidrogeológico tridimensional do aquífero de Ourém

Enquadra-se o aquífero de Ourém no Sinclinal de Ourém e na Bacia Lusitaniana. Propõe-se um modelo conceptual do aquífero de Ourém que tem em consideração a cota da base e do topo e a espessura da formação geológica que o constitui. Estabelece-se um paralelo entre os Membros da Formação da Figueira da Foz e as características hidrogeológicas do aquífero. Avalia-se o regime de exploração por métodos estatísticos robustos, de onde se concluiu que a captação de água desregulada tem levado a uma descida constante dos níveis piezométricos, atingindo em algumas áreas os 7 cm/mês, independentemente da precipitação anual nos últimos anos. Uma campanha de monitorização definiu o sentido NW-SE como o sentido preferencial de fluxo e a área NW do aquífero de Ourém como a área preferencial de recarga. Analisam-se qualitativamente as condições de fronteira do aquífero. ABSTRACT: A tridimensional conceptual model of the Ourém aquifer is defined, considering its top and bottom. The thickness of Figueira da Foz geological formation was calculated. A parallel between the Members of Figueira da Foz formation and hydrogeological characteristics of the aquifer is established. A robust statistical analysis concludes that the unregulated water abstraction of aquifer has led to a constant decrease of the piezometric levels. ln some areas the decreasing achieves 7 cm/month, independently of the annual rainfall. A piezometric monitoring campaign defines the NW-SE direction inside the preferential flow direction of the aquifer and the area NW of aquifer as the preferred aquifer recharge area. The aquifer boundary conditions are qualitatively evaluated.

Avaliação da vulnerabilidade à contaminação no sistema aquífero Évora-Montemor-Cuba

O principal objectivo desta dissertação é a aplicação de métodos empíricos para proceder à caracterização da vulnerabilidade à contaminação do Sistema Aquífero de Évora Montemor-Cuba, nomeadamente os índices DRASTIC, de Susceptibilidade (IS), GOD e o método EPPNA. A aplicação destes índices permitiu concluir que o Sistema Aquífero de Évora-Montemor-Cuba apresenta a maioria da sua área classificada com um índice de vulnerabilidade à contaminação baixo a moderadamente baixo, enquanto os aquíferos carbonatados apresentam grande parte da sua área classificada com um índice moderadamente alto a alto. O IS revelou-se uma ferramenta extremamente útil para ter uma visão espacial do território do ponto de vista da sua vulnerabilidade, quando associada aos usos do solo. No entanto, a complexidade dos sistemas naturais é sempre maior do que as simplificações necessárias para se poderem utilizar as ferramentas que permitem calcular estes índices, existindo permanentemente imprecisões associadas a estes cálculos. ABSTRACT: The aim of this Project is to apply different methods regarding the assessment of groundwater vulnerability to pollution in the Évora-Montemor-Cuba aquifer, namely the DRASTIC, IS, GOD and EPPNA. The greater area of the Évora-Montemor-Cuba aquifer has a vulnerability to pollution classified as low or moderate to low, while in the limestones aquifers the biggest area is classified as moderate to high or high. The IS index is a very useful tool to provide a spatial intuition of the territory, considering its vulnerability, when associated with the land use. However, the natural systems complexity is bigger than the necessary simplifications introduced in order to use these indexes, nevertheless there are permanent inaccuracies related to these results.