Muddy colored Douro river because of the clays

The muddy color of the Douro River, which has been causing curiosity to the population, is due to clays that, with heavy rains, dripped from the slopes. A natural and “great” phenomenon for the ecosystem, he explained to JN Adriano Bordalo e Sá, researcher and hydrobiologist at the Abel Salazar Institute of Biomedical Sciences (ICBAS).

With the heavy rains that were felt about two weeks ago with the Elsa and Fabien depressions, the soils became saturated and eventually became impermeable, he told JN Adriano Bordalo e Sá. With this phenomenon, and depending on the slope of the slopes, the waters of the tributaries of the Douro River flowed to the main course, along with the characteristic soil clays, giving the water a muddy color.

“All this clay has gone to the river. It’s great,” continued the hydrobiologist, clarifying that the clay “will naturally fertilize river water and then seawater.” That is, “enriching the waters and algae, which will develop in the spring thanks to a natural fertilizer.” The sardines will eat these algae and in St. John we will have very good sardines. It’s the working ecosystem, “added the hydrobiologist.

“These materials are normally retained in the dams. With the floods, it was necessary to relieve this water load and these materials will fertilize the river and the sea,” he said.

Fires left “bald” slopes

Also according to Bordalo and Sá, the fires of 2017 left much of the valley of the slopes “bald” and with a lot of coal, which was also taken to the Douro by rain. “But the coal from the fires also turns out to be positive because it helps control the acidity of river and sea water,” said the hydrobiologist.

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