Francisco Javier Sanz Ronda, teacher at Valladolid University, spoke about the impacts of the hydraulic works in the rivers. He checked the current state of civil works in the aquatic ecosystems. Above all the one of transversal Works as dams, which block rivers and affect changing the flow pattern of a river, because in winter rivers have low caudal and on summer the caudal is bigger.
“The aquatic organisms can’t adapt to this new pattern that is proportionate to them.” said Sanz Ronda, “Fishes have difficulty to move and go upriver because of these works. To help them, there are “escalas”, which are a type of steps with water that fishes go jumping to overcome the obstacle. The law obliges us to build them, but the problem is that their operation is never evaluated, because of that 95% of them don’t operate.”

In Spain there are some species that have been damaged because of these works. At the basin of the river Duero, eels have practically disappeard, but fifty years ago they could be fished anywhere. The Castilla and Leon government have released eels, but they don’t complete their cycle.
With regards to Avila, the current state is around the average of Spain.

Violeta Zazo