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Água na agricultura: um bem a preservar, um custo a rentabilizar: auditoria a um sistema de rega.
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Abstract(s)
A produção de alimentos e o uso de água estão intimamente relacionados, sendo este
o principal fator que limita a produção agrícola em vastas zonas do globo (FAO, 2012).
O setor agrícola é o maior consumidor de água doce, tanto à escala global como
nacional (Selborne, 2002), e, segundo o PNA, é responsável por cerca de 75% do
consumo deste recurso em Portugal.
Atualmente, em relação à temperatura do ar, verifica-se um aquecimento em todas as
estações do ano, acompanhado de ondas de calor com maior duração. No tocante à
precipitação, constata-se uma diminuição da precipitação anual, acompanhada, por
vezes, de fenómenos extremos de precipitação no outono/inverno e de secas com maior
duração na primavera/verão. É por isso expectável, pelo IPMA, que no futuro haja um
aumento de temperatura e um decréscimo de precipitação. As consequências desta
mudança climática estão-se já a verificar, a nível nacional, em que já há escassez de
água nos meses de primavera/verão, altura em que ela é mais necessária para a
agricultura (Pires, 2022).
Face a este cenário, entende-se que se torna necessário rentabilizar a aplicação da
água na agricultura, colocando-se o enfoque na melhoria de oportunidade de rega e da
eficiência de aplicação. Há uma necessidade crescente de redução de perdas de água,
por forma a se protegerem os recursos hídricos naturais e, consequentemente, o meio
ambiente (DGDR, 2014).
O objetivo deste trabalho consiste em elaborar um roteiro de auditoria à eficiência de
um sistema de rega por aspersão, através de rampa polar. Para analisar a sua
funcionalidade, fez-se em paralelo uma avaliação a um sistema de rega com rampa
polar e comparou-se os resultados obtidos com a respetiva carta de rega.
Apesar de só se conseguir ter acesso a um número reduzido de dados, estes foram
suficientes para chegar a conclusões sobre a eficiência da aplicação da água nas regas
efetuadas. Não se conseguiu quantificar os custos de aplicação de água em excesso
nas regas, essencialmente custos energéticos, nem a dimensão da pegada ecológica
da cultura, também por falta de dados para o efeito, embora se constatasse que houve
rega excessiva.
Food production and water use are closely related, which makes water use the main factor limiting agricultural production in vast areas of the globe (FAO, 2012). The agricultural sector is the largest consumer of freshwater, both globally and nationally (Selborne, 2002), and, according to the PNA, is responsible for around 75% of the consumption of this resource in Portugal. Currently, we are seeing an increase in the air temperature in all seasons of the year, accompanied by longer lasting heat waves. With regard to precipitation, there is a decrease in annual precipitation, sometimes accompanied by extreme precipitation phenomena in the autumn/winter and longer lasting droughts in the spring/summer. It is therefore expected, by the IPMA, that in the future there will be an increase in temperature and a decrease in precipitation. The consequences of this climate change are already being seen at a national level, where there is already a shortage of water in the spring/summer months, when it is most needed for agriculture (Pires, 2022). Considering this scenario, it is understood that it is necessary to optimize the application of water in agriculture, focusing on improving irrigation opportunities and application efficiency. There is a growing need to reduce water losses in order to protect natural water resources and, consequently, the environment (DGDR, 2014). The objective of this paper is to create an audit script for the efficiency of an irrigation system, using a pivot. To analyze its functionality, an evaluation of a pivot irrigation system was carried out in parallel and the results obtained were compared with the respective irrigation chart. Despite only being able to access a small data pool, these results were sufficient to reach conclusions about the efficiency of water application in the irrigation that were carried out. Due to the lack of data, it was not possible to quantify the costs of applying excess water in irrigation, essentially energy costs, nor the size of the ecological footprint of the crop, although it was found that there was excessive watering.
Food production and water use are closely related, which makes water use the main factor limiting agricultural production in vast areas of the globe (FAO, 2012). The agricultural sector is the largest consumer of freshwater, both globally and nationally (Selborne, 2002), and, according to the PNA, is responsible for around 75% of the consumption of this resource in Portugal. Currently, we are seeing an increase in the air temperature in all seasons of the year, accompanied by longer lasting heat waves. With regard to precipitation, there is a decrease in annual precipitation, sometimes accompanied by extreme precipitation phenomena in the autumn/winter and longer lasting droughts in the spring/summer. It is therefore expected, by the IPMA, that in the future there will be an increase in temperature and a decrease in precipitation. The consequences of this climate change are already being seen at a national level, where there is already a shortage of water in the spring/summer months, when it is most needed for agriculture (Pires, 2022). Considering this scenario, it is understood that it is necessary to optimize the application of water in agriculture, focusing on improving irrigation opportunities and application efficiency. There is a growing need to reduce water losses in order to protect natural water resources and, consequently, the environment (DGDR, 2014). The objective of this paper is to create an audit script for the efficiency of an irrigation system, using a pivot. To analyze its functionality, an evaluation of a pivot irrigation system was carried out in parallel and the results obtained were compared with the respective irrigation chart. Despite only being able to access a small data pool, these results were sufficient to reach conclusions about the efficiency of water application in the irrigation that were carried out. Due to the lack of data, it was not possible to quantify the costs of applying excess water in irrigation, essentially energy costs, nor the size of the ecological footprint of the crop, although it was found that there was excessive watering.
Description
Dissertação apresentada para a obtenção do grau de Mestre na área de Engenharia Agronómica, na Escola Superior Agrária de Santarém, Instituto Politécnico de Santarém, 2023
Keywords
Água na agricultura Eficiência de rega Eficiência energética Balanço hídrico Carta de rega Water in agriculture Irrigation efficiency Energy efficiency Hydric balance Watering chart
Citation
Ferreira, José Nicolau Nobre (2023). Água na agricultura: um bem a preservar, um custo a rentabilizar: auditoria a um sistema de rega. 53 p. Dissertação apresentada para a obtenção do grau de Mestre na área de Engenharia Agronómica, na Escola Superior Agrária de Santarém, Instituto Politécnico de Santarém.