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EnglishIn this work we analyze the surface water resources evolution in four stream flows, tributaries of the Douro river, since the second half of the XX century till the beginning of the XXI. The obtained results show a decrease in the total annual flow of the four rivers, even though this decrease was not statistically significant. This declining tendency is particularly remarkable after 1980.Except for autumn, in which a slight increase is verified, all the other seasons show regressive tendencies in overland flow, much more accentuated during winter and spring, although in summer, due to the deficit shown by these rivers, situations of high amount scarcity in water resources could be promoted. This annual decline in water resources, especially during the period in which the highest demand and the lowest quantity are registered, must be a subject for reflection, in order to avoid situations of water scarcity. portuguesNo presente trabalho analisa-se a evolucao dos recursos hidricos superficiais em quatro cursos de agua, tributarios do rio Douro, desde a segunda metade do seculo XX ate aos primordios do XXI. Os resultados obtidos mostram uma diminuicao no escoamento total anual dos 4 rios, embora em nenhum dos casos esse decrescimo seja estatisticamente significativo. Essa tendencia declinante e, particularmente, marcante apos 1980.Com excepcao do Outono, que verifica um ligeiro incremento, todas as outras epocas do ano manifestam tendencias regressivas nos escoamentos observados, mais relevantes no Inverno e na Primavera, embora no Verao, devido a acentuada estiagem manifestada por estes rios, possam ocorrer situacoes de elevada precariedade em termos de recursos hidricos. Esta diminuicao dos recursos, sobretudo nos periodos em que se regista um maximo de procura e um minimo em termos de disponibilidade, devera constituir materia de reflexao de modo a evitar situacoes de insuficiencia de agua.

Evolução recente dos recursos hídricos superficiais em 4 cursos de água tributários do rio Douro