Santillana Reservoir

The origin of the Santillana Reservoir is a real adventure that began in 1897, when the captain of engineers, Manuel del Río, planned supplying water and electricity to Colmenar Viejo with hydraulic jumps in the Manzanares River. A year later, in 1898, he received the right to use 2,000 litres of water per second from the river to serve not only Colmenar Viejo, but also Fuencarral and Madrid.

Joaquín de Arteaga y Echagüe, 18th Marquis of Santillana and 17th Duke of the Infantado, saw this project as a flourishing business and, in the same year, he acquired the rights and turned it into his personal company: he began the process of obtaining authorisations and rights to stretches of the flow of the Manzanares River, which he obtained in 1900; he presented the project for the enormous dam in 1902, and on 20th January 1905 he set up the Sociedad Anónima Hidráulica Santillana (Santillana Hydraulic Public Limited Company).

Although the dam and the hydraulic power stations did not start working until 1908 and did not serve Madrid until more than 10 years later, in 1907 the work was inaugurated in the presence of H.M. King Alfonso XIII, who placed the last stone in a symbolic act of ovation surrounded by great personalities of the time, such as Luca de Tena, Aguilar, the Count of Romanones, Segismundo Moret, the Marquis of Torrelaguna and Manuel García Prieto.

But the Santillana Reservoir was a hard blow for many residents of Manzanares El Real and its territory, as the creation of such a project entailed, from 1906, the forced expropriation of more than 37 private properties and part of the Dehesa Boyal de Colmenarejo, of municipal property and communal use, as well as the diversions of the road that led to Colmenar Viejo and several livestock trails. Thousands of hectares were flooded by the water that was dammed up, all the farmland and pasture of the fertile lowlands of Manzanares El Real that provided the livelihood of the town. The Sociedad Anónima Hidráulica Santillana paid compensation to all those affected, but the richest lands in the municipality were lost forever.

From 1965 onwards, a series of events took place that would bring about a complete turnaround in the Marquis’ company and result in its disappearance. In the same year, the need to increase the water supply to the capital became clear, so the powerful Canal de Isabel II became the majority shareholder of the Hidráulica and acquired control over it. Now the Canal had the rights to the entire flow of the Manzanares River and planned a new dam that would double the capacity of the previous one, making it disappear under the waters almost completely and would force, once again, the diversion of the road and several livestock tracks.

This modern rockfill dam, which we can see today at the Santillana reservoir, was built in less than a year and was inaugurated on the 14th of June, 1971. Given the strength the Canal acquired with this company, in 1990 it was transferred the complete management, exploitation, treatment and piping of the reservoir, which inevitably led to its definitive purchase in 1991.

After the construction of The Almendra Dam in Salamanca, the new Santillana Reservoir dam was a real milestone in Spanish engineering.

With a height of 40 metres, it collects the entire flow of the Manzanares River and allows accumulating twice the volume of water of the old dam, i.e. from 47.6 Hm3 collected by the previous one to 91.2 Hm3 by the new. But this fact, beyond the increase in supply capacity it provided, caused the old dam to be flooded almost in its entirety.

The first dam of the Santillana Reservoir, the one that created it and gives it its name, was not only a masterpiece in terms of the engineering knowledge of the time, but it was also conceived as an artistic monument which, today, and despite not being fully visible, still is a symbol of our municipality.

From a technical point of view, it was one of the first dams in Spain to be designed using Sazilly’s method, which improved the rational mechanics used to date and resolved perfectly the calculations needed to prevent the foundations from sliding, withstand the pressures and create a dam profile that it called of ‘equal resistance’. It is true that Sazilly conceived this method with stepped walls, which facilitated the calculation of pressure and resistance, but the engineers chose to soften the shape of our dam as Delocre did for the Furens Dam at Goufre d’Enfer. In addition, and to increase its resistance to the thrust of the water, they built its walls in two curved arches which they closed in the centre with the intake tower.

Beyond these technical aspects, so important in their time, the Renaissance aesthetics of this work stands out at first sight, transforming it into an artistic and cultural monument, since the whole complex was designed to be in harmony with the New Castle of the Mendoza family, inherited and owned by the Duke himself.

Like the castle, the dam was made of perfectly carved granite masonry, its walls were decorated and crowned with battlements in the barbican style; the gate on the left bank reproduces the entrance gate with the machicolations of the fortress and the intake tower, as well as reproducing this same gate at its base, rises in the same way as the octagonal keep.

In their eagerness to reproduce the fortified forms they respected the arrow slits, the stone muqarnas cornices, the crenellated crown and even the characteristic balls of the Isabelline Gothic style so typical of the 15th and 16th centuries. However, the highest part of the intake tower is particularly noteworthy, where the closed gallery is inspired by the same one that Juan Guas designed for the New Castle, as an example of the Toledan Gothic style that he himself established in Toledo Cathedral and in the Infantado Palace in Guadalajara.

Finally, we cannot fail to mention the coat of arms of the Mendoza lineage engraved in the centre of the main tower, whose aim was to give account, to anyone who approached it, of the owner of the reservoir and its territory.

Nobody could have ever imagined that, almost 100 years after its construction, the Santillana Reservoir would become one of the main aquatic bird reserve, protection, migration and nesting sites in the Community of Madrid.

As early as the 1960s, Félix Rodríguez de la Fuente, in his naturalistic and conservationist zeal, used to come to study the birds of the reservoir. In fact, such was his attachment to this place that he managed to build two observatories on the banks of the water to help disseminate knowledge and appreciation of the birds in the area.

Few people know that, from the beginning of the 20th century, the Duke repopulated the reservoir with fish on several occasions, introducing carp and pike, among others, and adapting this space for sport fishing and commercial fishing in the region. These fish introductions, in addition to the Mediterranean climate and increasingly mild temperatures, have made the Santillana Reservoir a particularly favourable place for migratory birds to spend the resting season here, and for some of them to settle and stay all year round.

The variety of birds that live and rest in the Santillana Reservoir is enormous, not in vain it was declared a Biosphere Reserve by UNESCO in 1993 as it belongs to the Cuenca Alta del Manzanares Regional Park, as well as being protected by the Regional Catalogue of Reservoirs and Wetlands of the Community of Madrid and being declared an IBA (Important Bird and Area).