CEF paper on the morphological diversity of the Portuguese Tagus River in the last 150 years

CEF paper on the morphological diversity of the Portuguese Tagus River in the last 150 years.
The Tagus River has lost morphological diversity over the last 150 years. This is the main conclusion of the study developed by the ForProtect and ForEco teams of the CEF Research Center published in Catena magazine.

In order to reconstruct the morphological change trajectories in the Portuguese Tagus River and to evaluate the consequences of the increasing hydrological regularization (construction of dams) and land use changes, the study analysed the river morphology from the 19th to the 21st century.
It focused on three different periods (1855, 1940 and 2000) and three distinct zones of the river (Zona Alta, between Vila Velha de Ródão and Belver, Zona Média, between Belver and Constância and Zona Baixa, between Constância and Vila Franca de Xira).

Schematic representation of the morphological evolution of the Tagus River and the changes in proximal land use, in each river zone, from the 19th to the 21st century

The results show significant morphological changes characterized by the reduction of islands and banks, narrowing of the channel, reduction of sinuosity and abandonment of the lateral river branches.
Most of these changes are related to the decrease in flood flows and the reduction of sediment caused by the increasing construction of dams. On the other hand, agricultural intensification, the increase of production forests and the decrease of Mediterranean scrubland are also factors responsible for changes in sediment dynamics and riverine connectivity.

The Upper Zone showed the greatest decline in morphological diversity, while the Middle Zone shows patterns of high variability. The Lower Zone reflects continuous but less pronounced changes.

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