Opposition to regrowth and its conditions
Since the Yesa dam regrowth plan was made public in 1983, which aims to build a new dam that would double the height of the current one and triple the current capacity of the reservoir, going from 490 hm³; to 1,500 hm³;, different oppositions to the work have been carried out by different associations of affected people headed by the Asociación Río Aragón") and COAGRET,[12] along with environmental associations such as Ecologistas en Acción, Greenpeace, SEO/BirdLife, WWF/Adena, AEMS-Ríos con Vida"), Friends of the Earth and which make up the platform "Yesa No")", oppose it. The opposition has They even reached courts where five legal actions have been opened, 3 administrative disputes, a criminal complaint against three former senior officials of the Ministry of the Environment and 1 complaint for the destruction of Historical-Artistic Heritage in reference to the Camino de Santiago, which has also been reported to UNESCO. The town councils of Jaca and Artieda have participated significantly in these actions.
All the sentences have ruled against the complainants, giving way to the construction of the new dam.
The organizations and associations opposed to the regrowth of the swamp point out that raising the crest level to 528 m would lead to serious effects on the towns in the valley. The urban area of Sigüés would be flooded and an area of important arable land would be lost, 1,560 hectares of dryland and 193 hectares of irrigated land in this municipality and those of Artieda and Mianos. The Foz de Sigües (protected area) would be affected by flooding to a large extent and the Sierras de Leyre, Orba and Illón would be affected, in addition to the SCI "Río Aragón", in which the disappearance of 771 hectares of trees stands out, especially 69 hectares of riverside vegetation among which are the "salguerales" ([willows]) of the mouth of the Esca and Aragón.
The flooding of the old landslide on the left slope, where large cracks have already appeared, endangers the physical integrity of the current dam. There is a 1999 report carried out by doctors in geology Antonio Casas Sainz and Mayte Rico,[13] from the Geology Department of the University of Zaragoza, which indicates the existence of a risk of dam failure. According to these same authors, the increase in dammed volume would increase the risk of earthquakes throughout the Berdún Channel, an area of known seismic activity. The CSIC Research Professor, Pedro Montserrat, has also warned of the danger of the slope.[14].
Likewise, opponents of the project indicate that part of the monumental heritage of the valley, crossed by the Camino de Santiago, would be affected.
The regrowth would seriously affect the following monuments:
• - Roman villa and medieval town of Corrales de Villarués.
• - Roman Villa of Rienda.
• - Roman villa of Viñas de Sastre.
• - Roman town of Forau de la Tuta and Campo del Royo.
• - Hermitage of San Pedro of the century.
• - Roman villa.
• - Romanesque hermitage of San Jacobo and archaeological remains of its necropolis.
• - Romanesque hermitage of San Juan Bautista.
• - Fountain of Santiago.
• - Medieval bridge.
• - Arroyo Vizcarra Necropolis.
• - Ruesta Roman necropolis and site.
• - Tower of the medieval castle.
• - Wall.
• - Romanesque church of San Esteban.
• - Santa Ana Hospital of the century.
• - Hermitage of San Juan Bautista.
• - Thermal baths from Roman times, which would remain inaccessible.
• - 15 km from the Sigüés-Esco-presa branch.
• - 7 km from the Artieda-Ruesta branch.[15].
Likewise, those opposed to regrowth emphasize the geological problems that have been occurring historically and which, according to them, could endanger the increased dam or make the constriction of the new one difficult.
They remember that with the commissioning of the current reservoir, in 1960 a landslide occurred on the right abutment of the dam that forced the road to be diverted and a large slope to be removed. Today, said abutment continues to have problems because leaks have been found that would endanger the foundation of the new dam.
But the most important geological problems are located on the left slope, with the existence of a paleoslide of 14 hm³, in the area of "La Refaya", which is at risk of moving if the dam increases.
Furthermore, during the construction work of a landfill on the track on the left bank, a landslide of 3.5 million cubic meters of earth occurred in August 2006, threatening to fall into the water and cause a tsunami-type wave that overflowed the dam, with catastrophic consequences for the inhabitants of Sangüesa (3,900 inhabitants). The Ebro Hydrographic Confederation (CHE) kept this fact hidden until[16] it made public a[17] report in February 2007 that recognized the landslide. During the summer of 2007 they opened[18]
new cracks and sinkholes in the area, and later the[19] track is unusable due to a large movement of earth. In view of what happened and the inability of the CHE to solve the problem, the Ministry of the Environment decides to put out to tender at the end of 2007 the carrying out of geological studies[20] of the slopes that will last at least one year.
• - Refaya paleoslide. Ancient slope movement of about 14 hm³, currently fossilized, located near the left abutment, but at risk of moving if Yesa regrowth.[13].
• - Landslide of 1930. On November 13, 1928, construction work on the current dam began. In 1930 the right slope fell while the abutment was being excavated.
• - Instability of the dam spillways 1957-1958. The terrain where the spillways have been built requires more surveys to be carried out and cement to be injected into the foundations. Due to its volume, the work had to be put out to tender in the BOE of September 16, 1957, and was awarded in the BOE of March 6, 1958.
• - Landslide of 1960. As a result of the filling of the reservoir and its subsequent unloading, the landslide of 1930 is reactivated. 60,000 m³ of earth are mobilized, affecting the newly built road, which requires a new route.
• - Landslide in 1964. During some rains the right slope falls down again.
• - Landslide on November 30, 2003. While the abutment of the left slope is being excavated, a crack 4 m wide and another 4 m deep appears, as well as flexual toppling type landslides measuring 45 m by 60 m.
• - Landslide of February 2004. The excavation of the slope of the right slope reactivates the landslides of 1930 and 1964.
• - Landslide in July 2006. The pressure exerted by the installation of a landfill on the left bank caused 3.5 million cubic meters of land to slide.
• - Summer landslide of 2007. In July 2007, the cracks and landslides of 2006 were repeated on the left slope.
• - Landslide in 2013 that forces the eviction of an urbanization in Yesa.