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Impactos das alterações climáticas nos recursos hídricos do Algarve
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As regiões mediterrânicas são bastante vulneráveis às alterações climáticas, o que se espera que resulte em temperaturas mais elevadas e diminuição da precipitação, com consequências para a evapotranspiração e, consequentemente, para a pressão sobre a água disponível para irrigação. A adaptação às alterações climáticas exige, portanto, mudanças na forma como os recursos hídricos são utilizados e no tipo de culturas que são irrigadas, a fim de conservar a água e manter uma agricultura sustentável. Este trabalho apresenta um estudo para a região do Algarve, no sul de Portugal. O principal objetivo é compreender como a oferta e o consumo de Recursos Hídricos irá (ou terá de) mudar num cenário mais árido. A análise centra-se nas bacias hidrográficas mais importantes da região e nas redes de irrigação correspondentes, composto por 3 sistemas de irrigação distintos; as culturas irrigadas são dominadas por pomares cítricos, milho, hortícolas e arroz. O balanço hídrico mensal foi calculado utilizando o modelo hídrico Thornthwaite Mather, que utiliza a precipitação, a evapotranspiração potencial, a retenção de água do solo e propriedades de geração de escoamento, a vegetação e as propriedades de utilização de água. Após a aplicação do modelo para a situação de referência (normal climatológica 1970-2005), os cenários futuros gerados foram divididos em três diferentes períodos: 2006-2040, 2041-2070, e 2071-2100. Foram considerados os cenários de emissões do RCP 4.5 (nível médio) e 8.5 (grave), conforme simulados por nove modelos climáticos regionais que utilizam resultados EUROCORDEX. Os resultados foram depois utilizados para compreender o stress hídrico através do Índice de Exploração de Água e identificar potenciais medidas de adaptação.
Mediterranean regions are highly vulnerable to climate change, which is expected to lead to lower precipitation and higher temperatures, with consequences for evapotranspiration demands and for the available water to meet them through irrigation. Adapting to climate changes therefore requires changes to how water resources are used, and on the type of crops selected for irrigation, in order to conserve water and maintain a sustainable agriculture. This work presents a study for the Algarve region in southern Portugal. The main objective is to understand how water resources’ supply and demand will (have to) change in a drier future. Therefore, the work focuses on the region’s most important reservoirs and the corresponding irrigation networks, comprising 3 distinct irrigation systems; irrigated cultures are dominated by citrus orchards, corn, green vegetables and rice. Monthly water balance was calculated using the Thornthwaite Mather sequential approach, which takes into account precipitation, potential evapotranspiration, soil water retention and runoff generation properties, and vegetation water use properties. The model was calibrated for one of the reservoirs and its corresponding irrigation network, and validated for a second reservoir-irrigation system. After the model application to present climatic conditions (1970-2005 climatic normal), future scenarios were simulated in three different periods: 2006-2040, 2041-2070, and 2071-2100. Emission scenarios RCP 4.5 (mid-level) and 8.5 (severe) were taken into account, as simulated by nine regional climate models using EUROCORDEX results, which will take into account both scenario and model uncertainty. The results were used to assess changes to water stress using the Water Exploitation Index, i.e. the rate of water demand over water supply, and to identify the most pressing adaptation needs for water conservation.
Mediterranean regions are highly vulnerable to climate change, which is expected to lead to lower precipitation and higher temperatures, with consequences for evapotranspiration demands and for the available water to meet them through irrigation. Adapting to climate changes therefore requires changes to how water resources are used, and on the type of crops selected for irrigation, in order to conserve water and maintain a sustainable agriculture. This work presents a study for the Algarve region in southern Portugal. The main objective is to understand how water resources’ supply and demand will (have to) change in a drier future. Therefore, the work focuses on the region’s most important reservoirs and the corresponding irrigation networks, comprising 3 distinct irrigation systems; irrigated cultures are dominated by citrus orchards, corn, green vegetables and rice. Monthly water balance was calculated using the Thornthwaite Mather sequential approach, which takes into account precipitation, potential evapotranspiration, soil water retention and runoff generation properties, and vegetation water use properties. The model was calibrated for one of the reservoirs and its corresponding irrigation network, and validated for a second reservoir-irrigation system. After the model application to present climatic conditions (1970-2005 climatic normal), future scenarios were simulated in three different periods: 2006-2040, 2041-2070, and 2071-2100. Emission scenarios RCP 4.5 (mid-level) and 8.5 (severe) were taken into account, as simulated by nine regional climate models using EUROCORDEX results, which will take into account both scenario and model uncertainty. The results were used to assess changes to water stress using the Water Exploitation Index, i.e. the rate of water demand over water supply, and to identify the most pressing adaptation needs for water conservation.
Descrição
Tese de mestrado em Ecologia e Gestão Ambiental, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, em 2018
Palavras-chave
Thornthwaite Mather Clima Mediterrâneo Agricultura irrigada Cenários RCP 4.5 e RCP 8.5 Bacias hidrográficas Teses de mestrado - 2018