A carregar...
Publicação
Metodologia de estimação da extração de água subterrânea em regadios individuais: MEESRI
| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 15.76 MB | Adobe PDF |
Autores
Resumo(s)
Em Portugal, o sector agrícola constitui o principal utilizador de água subterrânea, destacando-se os regadios de iniciativa individual com maior representatividade em volume extraído. Face à escassez hídrica que afeta de forma recorrente as regiões mediterrânicas, impõe-se uma gestão criteriosa dos aquíferos. O presente trabalho tem como objetivo o desenvolvimento de uma metodologia para aestimação indireta da extração de água subterrânea em regadios individuais na ausência de registos. A metodologia inclui uma base de dados georreferenciada contendo informação edafoclimática, cultural e dos sistemas de rega. A utilização de imagens de satélite de alta resolução espacial e temporal permite a identificação das culturas e dos ciclos vegetativos, alimentando o modelo ISAREG para o balanço hídrico do solo. A metodologia apresenta ainda um módulo onde são efetuadas as correspondências entre as captações de água subterrânea identificadas e as áreas regadas para as quais ela contribui, de modo a ser possível estimar o volume de água extraído em cada captação. A metodologia foi aplicada a um caso de estudo na região da Golegã, tendo sido feita a sua validação por comparação com os correspondentes volumes medidos em caudalímetros instalados em 20 furos agrícolas. Os resultados indicam extrações de 4.500 a 7.700 m³ ha⁻¹, dependendo do ciclo da cultura do milho e do sistema de rega, com erro médio quadrático relativo de 9,3%. Os coeficientes de determinação entre valores estimados e medidos variam entre 0,919 e 0,928, indicando forte correlação e demonstrando que a metodologia representa adequadamente a variabilidade nas extrações. A metodologia mostrou-se uma ferramenta promissora para a gestão quantitativa da água subterrânea, permitindo monitorizar consumos em larga escala a baixo custo operacional. Identificaram-se aspetos que deverão ser melhorados em trabalhos futuros, tais como a suscetibilidade à cobertura de nuvens, a sensibilidade à variabilidade espacial dos solos e o estabelecimento das correspondências entre as captações e as respetivas áreas regadas.
In Portugal, the agricultural sector is the main user of groundwater resources, where irrigation systems supplied by individual/private water sources (farmer-owned boreholes or wells) account for the largest share. Given the recurrent water scarcity affecting Mediterranean regions, an efficient management of aquifers is imperative. The present study aims to develop a methodology for the indirect estimation of groundwater abstraction in irrigation systems supplied by individual/private water sources in the absence of direct measurement records. The methodology integrates a georeferenced database containing edaphoclimatic, crop-specific, and irrigation system information. The use of high-resolution satellite imagery, both spatially and temporally, enables the identification of crop types and growth cycles, which feed into the ISAREG model for the soil water balance calculation. Additionally, the methodology includes a module that establishes correspondences between identified groundwater abstraction points and the irrigated areas to which they contribute, thereby allowing the estimation of the volume abstracted at each point. The methodology was applied to a case study in the Golegã region and validated through comparison with measured volumes from flow meters installed in 20 agricultural wells. Results indicate abstraction values ranging from 4,500 to 7,700 m³ ha⁻¹, depending on the crop cycle and irrigation system, with a relative root mean square error of 9.3%. Coefficients of determination between estimated and measured values ranged from 0.919 to 0.928, indicating a strong correlation and demonstrating the methodology’s ability to adequately represent the variability in groundwater abstraction. The methodology proved to be a promising tool for quantitative groundwater management, enabling large-scale monitoring of water use with low operational costs. Several aspects were identified for future improvement, such as susceptibility to cloud cover, sensitivity to spatial variability in soil properties, and the refinement of correspondences between abstraction points and their respective irrigated areas.
In Portugal, the agricultural sector is the main user of groundwater resources, where irrigation systems supplied by individual/private water sources (farmer-owned boreholes or wells) account for the largest share. Given the recurrent water scarcity affecting Mediterranean regions, an efficient management of aquifers is imperative. The present study aims to develop a methodology for the indirect estimation of groundwater abstraction in irrigation systems supplied by individual/private water sources in the absence of direct measurement records. The methodology integrates a georeferenced database containing edaphoclimatic, crop-specific, and irrigation system information. The use of high-resolution satellite imagery, both spatially and temporally, enables the identification of crop types and growth cycles, which feed into the ISAREG model for the soil water balance calculation. Additionally, the methodology includes a module that establishes correspondences between identified groundwater abstraction points and the irrigated areas to which they contribute, thereby allowing the estimation of the volume abstracted at each point. The methodology was applied to a case study in the Golegã region and validated through comparison with measured volumes from flow meters installed in 20 agricultural wells. Results indicate abstraction values ranging from 4,500 to 7,700 m³ ha⁻¹, depending on the crop cycle and irrigation system, with a relative root mean square error of 9.3%. Coefficients of determination between estimated and measured values ranged from 0.919 to 0.928, indicating a strong correlation and demonstrating the methodology’s ability to adequately represent the variability in groundwater abstraction. The methodology proved to be a promising tool for quantitative groundwater management, enabling large-scale monitoring of water use with low operational costs. Several aspects were identified for future improvement, such as susceptibility to cloud cover, sensitivity to spatial variability in soil properties, and the refinement of correspondences between abstraction points and their respective irrigated areas.
Descrição
Dissertação de Mestrado, Engenharia Agronómica, 2025, Universidade de Lisboa, Instituto Superior de Agronomia.
Palavras-chave
necessidades de rega sistemas de rega deteção remota balanço hídrico do solo modelação irrigation requirements irrigation systems remote sensing soil water balance modelling