The Douro, the third longest river in the Iberian peninsula, rises in the Spanish province of Soria and flows into the Atlantic between Oporto and Vila Nova de Gaia. Once a free and wild river, with impetuous flow rates in winter and minor in summer due to the Mediterranean-type climate of much of the territory that crosses, it was tamed with the construction of several dams, five in Portuguese territory built between 1972 and 1985.

Between the dams, the river's waters are now calm, only stirred by the wind and by the passage of one or another vessel, which may be of reasonable dimensions and cause some momentary swell. How can we capture so much placidity in the waters of these lakes formed between the dams? Using long exposure times in environments that should be as static as possible.

While wandering along the banks of the river a few days ago, on a very still late afternoon, with almost no wind, I was surprised by this landscape, with the sun hitting a small beach, the ash trees almost motionless, a slight breeze stirring a few branches, and tiny waves that broke on the beach. Using eight seconds of exposure time (and an ND 64 filter), the river water appears to us as a large liquid mass of wonderful blue color, with a surface that is either dull or mirrors the vegetation on the banks.