Yesa Reservoir

The Yesa Reservoir lies at the foot of the Sierra de Leyre in the Navarrese-Aragonese Pre-Pyrenees, with a water surface that can reach 2,089 hectares at full capacity. Known as the Sea of the Pyrenees, the reservoir was inaugurated in 1960 after the dam was built on the Aragón River in the Navarrese municipality of Yesa, although most of its surface area falls within the province of Zaragoza. Stretching 10 kilometres long and between 1 and 2.5 kilometres wide, it holds 447 cubic hectometres and is the largest navigable surface in Aragón.

The reservoir landscape shifts with the seasons and water level. In spring and early summer, when Pyrenean snowmelt fills the basin, the turquoise waters reflect the Sierra de Leyre to the south and the Pyrenean foothills to the north, with tones closer to an Alpine lake than a peninsular reservoir. In autumn, as the level drops after the irrigation season, the ruins of the village of Tiermas emerge and, if the reservoir falls below 29 per cent of capacity, the remains of an ancient Roman spa surface with its sulphurous thermal springs. This cycle of submersion and reappearance makes Tiermas one of the most singular landscapes in the Ebro basin.

Water sports are the reservoir's main draw. The cierzo — a north wind that blows strong and gusty through the sierra — creates reliable conditions for dinghy sailing, windsurfing and kitesurfing. Water skiing, powerboating and kayaking are also practised. Sport fishing attracts enthusiasts year-round: the reservoir supports populations of trout, carp, pike and perch. The shores, accessible at several points from the N-240 running along the right bank, offer informal swimming spots during summer, though there are no serviced beaches.

The reservoir surroundings connect to hiking and cycling routes following paths between the villages the dam left behind. From Artieda, a wooded stretch of the Aragonese Camino de Santiago runs along the shore to Ruesta, a village uninhabited since the 1960s that retains a Romanesque church and a restored pilgrim hostel. The Sierra de Leyre to the south offers trails through beech and pine woods with views over the reservoir, and the Monastery of Leyre — founded in the 9th century — is a 10-minute drive from the dam. The municipalities of Sigüés, Salvatierra de Esca and Sangüesa (16 km away) provide accommodation, dining and access to other local attractions such as the Foz de Lumbier and Foz de Arbayún gorges.

The reservoir's history is bound up with the villages it submerged. Construction of the dam between 1928 and 1960 forced the evacuation of over 1,500 people from settlements including Tiermas, Ruesta and Escó. The 8,528 expropriated hectares were shared among the municipalities of Sigüés, Urriés, Undués de Lerda and Los Pintanos. That memory of displacement is as much part of the landscape as the water itself: the walls that emerge in autumn are not just a curiosity but a reminder of communities relocated so that the Bardenas Canal could bring water to the fields of southern Navarra.

The Yesa Reservoir works as a rest point for families and watersports enthusiasts seeking an accessible mountain setting. The combination of water, Pre-Pyrenean landscape and medieval heritage creates a destination usable year-round: watersports and swimming in summer, fishing and hiking in autumn and spring, and winter scenery with the snow-capped sierra as a backdrop.