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Publication
Seleção de potenciais locais para a implantação de reservatórios de água para o apoio à agricultura no concelho de São Brás de Alportel
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Abstract(s)
No concelho de São Brás de Alportel por forma a fomentar a prática da agricultura de regadio, torna-se necessário proceder-se à construção de reservatórios para a acumulação de água de origem superficial.
Foi fundamental iniciar este trabalho caraterizando esta região por isso numa primeira fase, procedeu-se à descrição do clima, da rede viária, da geologia, dos solos, da hidrografia, da agricultura do concelho.
Com recurso à Deteção Remota e a Sistemas de Informação Geográfica começaram por ser identificadas as parcelas de regadio do concelho. O estudo foi desenvolvido a partir da aquisição, processamento e análise de imagens de Índice da Diferença Normalizada e Índice de Humidade da Diferença Normalizada de verão e inverno do satélite Sentinel-2, aplicando técnicas de processamento de imagem para extração das áreas de regadio.
Com recurso aos modelos digitais de elevação foram delimitadas as bacias hidrográficas. Foi realizada uma caracterização das mesmas e foi possível obter os dados relativos às características da rede de drenagem e direções do escoamento.
Identificaram-se áreas propícias para a construção de reservatórios, considerando variáveis específicas na tomada de decisão. Os critérios incluíram a localização a uma distância superior a 100 metros da rede viária e de linhas de alta tensão, a exclusão de áreas situadas nos polígonos destinados à agricultura no concelho e a preferência pela zona da serra devido às características do solo que asseguram uma menor impermeabilização do fundo, resultando em custos reduzidos.Por fim, foi calculado o balanço hidrológico dos reservatórios com vista a estimar a capacidade de armazenamento e disponibilidade hídrica para a rega ao longo do ano.
Neste estudo, de facto, é apresentado um exemplo de como a elaboração do balanço hidrológico pode ser apoiada nos SIG e de como pode ser construída uma base de apoio na gestão de recursos hídricos para o abastecimento da agricultura.
In the municipality of São Brás de Alportel, in order to encourage the practice of irrigated agriculture, it is necessary to build surface water reservoirs. It was essential to begin this work by characterising the region, so the first step was to describe the climate, road network, geology, soils, hydrography and agriculture of the municipality. Remote Sensing and Geographic Information Systems were used to identify irrigated plots in the municipality. The study made by acquiring, processing and analysing summer and winter Normalized Difference Vegetation Index and Normalized Difference Moisture Index images from the Sentinel-2 satellite and applying image processing techniques to extract the irrigated areas. Using digital terrain models, the river basins were delimited and an exhaustive characterization of the basins was obtained, from which it was possible to obtain data on the characteristics of the drainage network, in which the flow directions were defined. Favourable areas were found for the construction of reservoirs. The variables included in the choice were: location more than 100 metres from the road network and high voltage power lines, being outside the polygons that correspond to the existing agriculture in the municipality, and the best conditions for building a reservoir were found to be in the mountains. Finally, the hydrological balance of the reservoirs was calculated in order to estimate storage capacity and water availability for irrigation throughout the year. In fact, this study provides an example of how the preparation of the hydrological balance can be supported by GIS and how a basis can be built to support the management of water resources for agricultural supply.
In the municipality of São Brás de Alportel, in order to encourage the practice of irrigated agriculture, it is necessary to build surface water reservoirs. It was essential to begin this work by characterising the region, so the first step was to describe the climate, road network, geology, soils, hydrography and agriculture of the municipality. Remote Sensing and Geographic Information Systems were used to identify irrigated plots in the municipality. The study made by acquiring, processing and analysing summer and winter Normalized Difference Vegetation Index and Normalized Difference Moisture Index images from the Sentinel-2 satellite and applying image processing techniques to extract the irrigated areas. Using digital terrain models, the river basins were delimited and an exhaustive characterization of the basins was obtained, from which it was possible to obtain data on the characteristics of the drainage network, in which the flow directions were defined. Favourable areas were found for the construction of reservoirs. The variables included in the choice were: location more than 100 metres from the road network and high voltage power lines, being outside the polygons that correspond to the existing agriculture in the municipality, and the best conditions for building a reservoir were found to be in the mountains. Finally, the hydrological balance of the reservoirs was calculated in order to estimate storage capacity and water availability for irrigation throughout the year. In fact, this study provides an example of how the preparation of the hydrological balance can be supported by GIS and how a basis can be built to support the management of water resources for agricultural supply.
Description
Keywords
Município de São Brás de Alportel Bacia hidrográfica Deteção remota Índices de vegetação Sistemas de informação geográfica