The Sénia river originates vehemently in the Els Ports mountains. It quickly falls into the Ulldecona reservoir and from this point it slows down, although it receives water from other smaller ravines that bring water in spring and autumn.
After leaving Els Ports, the river enters a very flat terrain and the surface water disappears, except for floods or heavy rains. It is not until the estuary that the water resurfaces, in this case throughout the year, in a shape of a long lagoon.
The Sénia estuary is a space of natural and landscape interest recognised as such owing to a wide variety of plant and animal species and to its position between the Ebro Delta and the Albufera of Valencia, which turns it into a stopping place for migratory birds.
The waters of the lagoon, fed by aquifers, receive marine intrusions mainly in the driest months, when the water tables lower their level. That is why we find plenty of vegetation typical of lagoons and rivers, such as reeds, rushes, ash trees and white willows.
On the banks of the lagoon, where the soil is rockier and not too deep, we find some shrubland formed by mastic trees, kermes oaks and dwarf palms (Europe’s only autochthonous palm). In contrast, on the river’s slopes and banks we find coastal vegetation such as fennel.
In addition, this corner houses a great variety of fauna typical of Mediterranean wetlands such as toads, moorhens, swallow ducks, seagulls, cormorants and even Mediterranean turtles, who we can see, with some luck, warm up on the pebbles. Its presence indicates this place’s excellent environmental quality.