The presence of oil was detected on January 14, 2006 by an environmental agent of the Junta de Castilla y León, downstream of the Linares del Arroyo Reservoir dam, affecting about 200 m. of the middle section of the Riaza, at the height of the municipality of Maderuelo (Segovia). The section of polluted river is located inside the Raptor Refuge managed by the Duero Hydrographic Confederation (CHD) which, together with the Montejo de la Vega Raptor Refuge, managed by WWF/Adena, are integrated into the Hoces del Río Riaza Natural Park.

The leak, which comes from the Hydroelectric Station located at the foot of the reservoir dam and whose operation is granted to the company Unión Fenosa, has been practically controlled thanks to the rapid intervention of the Board’s nursery, as well as the Confederation itself and Unión Fenosa, which have deployed the necessary technical and human resources to eliminate all traces of spillage.

So far, no type of impact on aquatic fauna has been detected, although it is true that the exact composition of the spilled substance is unknown. Thus, in its complaint WWF/Adena demands that the appropriate analyses be carried out to determine any possible impact on the quality of the river’s water, as well as on the existing flora and fauna. Likewise, WWF/Adena has called on the Confederation to open an investigation, to clarify the origin of the polluting substance and determine those responsible for the spill, both to prevent them from reproducing in the future, and to apply the appropriate sanction to the entity responsible.