Publication
Avaliação do sistema hidrográfico do Graben das Lages
| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| Resumo, Índice, Introdução | 230.71 KB | Adobe PDF | ||
| Documento Principal | 4.7 MB | Adobe PDF |
Authors
Abstract(s)
O Graben das Lajes é uma depressão tectónica, localiza-se na vertente NE do vulcão dos Cinco Picos, entre a escarpa das falhas das Fontinhas a SW e de Santiago a NE. Do ponto de vista hidrogeológico esta zona está associada ao troço mais oriental do aquífero de base da ilha Terceira, recarregado, em grande parte, nas zonas centrais da ilha onde a precipitação é mais elevada. Para além do aquífero basal o Graben das Lajes comporta duas massas de água subterrâneas suspensas localizadas a profundidades distintas. Na zona litoral SW do Graben das Lajes existem três zonas lagunares associadas a descargas das massas de água acima referidas – os pauis da Praia da Vitória, Belo Jardim e Pedreira do Cabo da Praia. Estas massas de água superficiais têm particular importância ecológica, dada a sua grande biodiversidade.
No sentido de conhecer com detalhe esta zona a nível hidrológico, o presente trabalho tem como objetivo: determinar o sentido do fluxo hídrico nos aquíferos suspensos e de base; compreender os processos de recarga, circulação e descarga, e a influência que a tectónica tem nestes processos; avaliar qualitativamente a água basal dos furos de captação para consumo humano e da água superficial dos três pauis; e por fim determinar o estado trófico dos Pauis da Praia da Vitória, Belo Jardim e Pedreira do Cabo da Praia.
A metodologia seguida neste trabalho comportou um inventário detalhado de pontos de água, medições de níveis hidrostáticos nos furos e poços e uma avaliação qualitativa da água do aquífero basal, a montante, com base em dados de furos de captação fornecidos pela empresa Praia Ambiente, e a jusante, nos próprios pauis, utilizando-se elementos cedidos pelo Projeto LIFE CWR. Utilizou-se como referência qualitativa a legislação portuguesa em vigor para os parâmetros de qualidade de água. Nos casos em que esta é omissa seguiram-se as normas aplicadas no Canada e Holanda. Na determinação do estado trófico nos três pauis utilizaram-se dados da concentração de fósforo total e foram aplicados dois índices, o índice do estado trófico de Carlson (1977) modificado por Toledo (1983) e o de Lamparelli (2004).
No seguimento do estudo do sentido do fluxo hídrico, admite-se a existência de uma subdivisão do Graben da Lajes em três plataformas distintas, a plataforma das Fontinhas, a plataforma das Lajes e a plataforma do Juncal, considerou-se que estas falhas que dividem estas plataformas são parcialmente impermeáveis, tendo um papel fundamental na direção do fluxo. A impermeabilidade das falhas tectónicas muda a direção do fluxo dentro da zona, contrariando o fluxo radial admitido para regiões insulares.
Na análise qualitativa da água para consumo humano registaram-se duas concentrações acima dos valores paramétricos legais nacionais e estrangeiros: manganês e hidrocarbonetos, ambas no furo do Areeiro. Qualitativamente, a água dos três pauis, encontra-se em conformidade com a legislação utilizada como referência, sendo registada apenas uma concentração de arsénio, cádmio e chumbo acima destes valores.
Quando aplicados os índices tróficos aos três pauis, concluiu-se que todos se encontravam eutrofizados em 2016 e 2017. O fósforo nos três pauis terá proveniências diferentes das descritas na literatura, chegando principalmente por via subterrânea aos corpos de água e não por escoamento superficial como acontece em lagos com caraterísticas semelhantes.
ABSTRACT: Lajes Graben is a tectonic depression, located in the NE slope of the Five Peaks volcano, between Fontinhas fault to SW and Santiago’s fault to NE. From the hydrogeological point of view, this zone is associated with the easternmost section of the Terceira Island basal aquifer, recharged in large part in the central zones of the island where precipitation is highest. In addition to the basal aquifer the Lajes Graben contains two perched groundwater bodies located at different depths. In the SW coastal area of the Lajes Graben there are three lagoons associated with discharges of the above mentioned water masses - the wetlands of Praia da Vitória, Belo Jardim and Pedreira do Cabo da Praia. These surface water bodies are of particular ecological importance given their great biodiversity. In order to know this zone in detail at the hydrological level, the present work aims to: determine the direction of the water flow in the perched and basal aquifers; understand the processes of recharge, circulation and discharge, and the influence that tectonics has on these processes; to evaluate qualitatively the basal water of wells for human consumption and the surface water of the three wetlands; and finally determine the trophic status of the wetlands of Praia da Vitória, Belo Jardim and Pedreira do Cabo da Praia. The methodology followed in this work included a detailed inventory of water points, measurements of hydrostatic levels in the wells and wells and a qualitative assessment of basement aquifer water, upstream, based on data from wells supplied by Praia Ambiente, and downstream, in the wetlands itself, using elements provided by the LIFE CWR Project. The Portuguese legislation for water quality parameters was used as a qualitative reference. In cases where this is omitted, the standards applied in Canada and the Netherlands have been followed. In the determination of the trophic state in the three wetlands, total phosphorus concentration data were used and two indices were applied, the Carlson (1977) modified by Toledo (1983) and Lamparelli (2004) index. Following the study of the direction of the water flow, the existence of a subdivision of the Lajes Graben in three different platforms, the platform of the Fontinhas, the platform of the Lajes and the platform of the Juncal, was admitted that these faults that divide these platforms are partially impermeable, playing a key role in the flow direction. The impermeability of tectonic faults changes the flow direction within the zone, counteracting the admitted radial flow to island regions. In the qualitative analysis of water for human consumption, there were two concentrations above national and foreign legal parametric values: manganese and hydrocarbons, both in the Areeiro well. Qualitatively, the water of the three wetlands is in accordance with the legislation used as reference, with only a concentration of arsenic, cadmium and lead being recorded above these values. When the trophic indexes were applied to the three wetlands, it was concluded that all of them were eutrophicated in 2016 and 2017. The phosphorus in the three wetlands will have different origins than those described in the literature, arriving mainly by underground water bodies and not by surface runoff as happens in lakes with similar characteristics.
ABSTRACT: Lajes Graben is a tectonic depression, located in the NE slope of the Five Peaks volcano, between Fontinhas fault to SW and Santiago’s fault to NE. From the hydrogeological point of view, this zone is associated with the easternmost section of the Terceira Island basal aquifer, recharged in large part in the central zones of the island where precipitation is highest. In addition to the basal aquifer the Lajes Graben contains two perched groundwater bodies located at different depths. In the SW coastal area of the Lajes Graben there are three lagoons associated with discharges of the above mentioned water masses - the wetlands of Praia da Vitória, Belo Jardim and Pedreira do Cabo da Praia. These surface water bodies are of particular ecological importance given their great biodiversity. In order to know this zone in detail at the hydrological level, the present work aims to: determine the direction of the water flow in the perched and basal aquifers; understand the processes of recharge, circulation and discharge, and the influence that tectonics has on these processes; to evaluate qualitatively the basal water of wells for human consumption and the surface water of the three wetlands; and finally determine the trophic status of the wetlands of Praia da Vitória, Belo Jardim and Pedreira do Cabo da Praia. The methodology followed in this work included a detailed inventory of water points, measurements of hydrostatic levels in the wells and wells and a qualitative assessment of basement aquifer water, upstream, based on data from wells supplied by Praia Ambiente, and downstream, in the wetlands itself, using elements provided by the LIFE CWR Project. The Portuguese legislation for water quality parameters was used as a qualitative reference. In cases where this is omitted, the standards applied in Canada and the Netherlands have been followed. In the determination of the trophic state in the three wetlands, total phosphorus concentration data were used and two indices were applied, the Carlson (1977) modified by Toledo (1983) and Lamparelli (2004) index. Following the study of the direction of the water flow, the existence of a subdivision of the Lajes Graben in three different platforms, the platform of the Fontinhas, the platform of the Lajes and the platform of the Juncal, was admitted that these faults that divide these platforms are partially impermeable, playing a key role in the flow direction. The impermeability of tectonic faults changes the flow direction within the zone, counteracting the admitted radial flow to island regions. In the qualitative analysis of water for human consumption, there were two concentrations above national and foreign legal parametric values: manganese and hydrocarbons, both in the Areeiro well. Qualitatively, the water of the three wetlands is in accordance with the legislation used as reference, with only a concentration of arsenic, cadmium and lead being recorded above these values. When the trophic indexes were applied to the three wetlands, it was concluded that all of them were eutrophicated in 2016 and 2017. The phosphorus in the three wetlands will have different origins than those described in the literature, arriving mainly by underground water bodies and not by surface runoff as happens in lakes with similar characteristics.
Description
Mestrado (Trabalho de Projeto), Engenharia e Gestão de Sistemas de Água, 19 de julho de 2019, Universidade dos Açores.
Keywords
Aquífero Fluxo Hídrico Qualidade da Água Ilha Terceira (Açores) Açores Aquifer Water Flow Water Quality Azores
Citation
Pimentel, César Miguel Meneses. "Avaliação do Sistema Hidrográfico do Graben das Lages". 2019. 137 p.. (Mestrado em Engenharia e Gestão de Sistemas de Água). Angra do Heroísmo: Universidade dos Açores, 2019. [Consult. Dia Mês Ano]. Disponível em www:<http://hdl.handle.net/10400.3/5422>.