El arca del agua | Sitios Culturales en el Geoparque VIJ

The Arca del Agua is one of the most valuable engineering legacies of all the works of the Hieronymites scattered over the Villuercas-Ibores-Jara Global Geopark of the UNESCO. With the aim of exploiting and distributing the water of springs, in the 14th century a true work of art of medieval hydraulic engineering was constructed that still works perfectly. For many centuries this work, which penetrates the depths of the sierra, has allowed both the Real Monasterio de Guadalupe and nearby kitchen gardens, palaces, houses, and hospitals to enjoy cool drinking water from the springs of the sierra all year round. There is no doubt that it was one of the mainstays of the prosperity of the site. It is considered to be the oldest hydraulic system still in use in Spain.

Some six kilometres from Guadalupe on the road to Navalmoral de la Mata and then on a track leading west from the Chapel of the Humilladero lies the Arca del Agua, an exceptional piece of engineering with seven centuries of history. It is one of the geosites of the Villuercas- Ibores-Jara Global Geopark of the UNESCO and despite its interest and importance may pass unnoticed as most of its structures are underground. The construction of the Arca del Agua was completed in 1350. Broadly speaking it consists of a complex system for capturing underground water in order to channel it to the Real Monasterio and the town of Guadalupe.

The main capture consists of a series of underground galleries dug out of the rock covered with slate or vaulted with brick, called water mines, which drain the water from various springs mainly located on the south and east hillsides of the crag of La Villuerca. On these slopes the contact between the quartzite rocks and those with a slate component give rise to fissures through which the underground water spurts as springs, ‘veneros’ or ‘manaeros’.

The water from these galleries is led to the Arca del Agua proper which consists of a cistern with a pointed barrel vault. This cistern is built of granite and near its entrance there is a 16th-century bronze plaque which indicates that the secrets of the ‘manaderos’ which supply the Arca del Agua have been written down and are kept at the monastery. Most of the Arca is below ground level so that the water reaches its destination by gravity. The water accumulated is filtered for possible impurities in this cistern and in the so-called ‘arquillo’.

Once the Arca was full its water fell by its own weight to a channel made of pipes of baked clay which took it towards Guadalupe. Along its route a series of vents had been placed to avoid the accumulation of air in the pipes and thus regulate the pressure. This channelling system extends over six kilometres and is completed with a tunnel of two hundred metres excavated beneath the Cerro Miramontes, which is also known as ‘Cerro Huracao’ or ‘Cerro Horadado’.
Once the water reached the town of Guadalupe it was distributed by a system of minor channels to fountains, troughs, and kitchen gardens to make the crystal-clear water which sprouted from the springs of the sierra available all year round for the use of the inhabitants of the Monasterio and of Guadalupe. Even today the water of fountains such as that of the cloister of the monastery, that of the Plaza de Santa María, and that of the Tres Chorros comes from the Arca del Agua.

In the designing of this complex work of engineering the precepts already indicated by the ancients were taken into account, for health reasons the water from prevented from seeing the light at any time before it left the spout of the fountain. The monks themselves considered it to be the most important work of Guadalupe according to a codex which describes it: “The channelling of this water is the most important thing and the main and oldest heritage of this institution”.