GET TO KNOW GRAN CANARIA / IT´S GRAN CANARIA
The water landscape in Gran Canaria is made up of thousands of hydraulic works built to ensure the maximum use of superficial water supplies (piping, ponds, dams) and the accessing of groundwater (mines, adits and wells). The many hydraulic companies are a sign of the laborious work carried out on the island, although many of their constructions fade somewhat into the island’s heterogeneous features, namely vegetation, farming, villages, houses, roads, and so on. Therefore, the works that are easiest to spot and to visit are those dams with reservoirs with an altitude superior to 15 metres from the lowest point of their foundations up to the highest point of their resistant structure: the so called large dams.
Despite the technical difficulties involved in blocking off the flow of water of a ravine, 78 large dams were constructed during the 20th century, although up to 329 reached the design stage. These two figures are enough to gauge the importance of the efforts made to capture and/or store water by means of large dams here on an island that measures barely 1,560 km², hence the expression the land is the least of our concerns, what is important is water. Of all the large dams, the one to highlight is the construction of Soria dam, the only arch dam built on the Canary Archipelago, and standing at a lofty 132 metres, putting it among the highest dams in Spain.
Construction on the dam began before the first concessions were given to the San Lorenzo and Pinto dams in 1904. The need to have greater water flow to enable the watering of farmland made the digging of the foundations, the first few metres of the wall and a number of other accessory works (water feeds, channels, piping, tunnels, etc.) we made prior to any authorisation being granted by the Public Works Department. San Lorenzo suffered an incident during its construction when water revealed a single crack in the ground that had been around since time immemorial, meaning the dam was left unfinished until its height was later raised in the 1960s; while the Pinto dam in Arucas, whose construction was finished in 1910 and is the oldest dam in the Canary Islands, inspired other private parties to build their own dams at other similar ravines in the north of Gran Canaria. The coastline, which at the end of the 19th century was barren and unproductive, became highly productive fertile terrain in the 1950s, with agriculture almost being carried out on a gardening level.
The bodies of the oldest dams at Pinto, Marquesa, Hormiguero, Cueva Grande, Sabinal, Cuevas Blancas, and so on, were built of masonry using lime mortar, while the complete and long-lasting impermeability of the upper facing was achieved with a simple plastering of lime mortar and cement. In general, nearly all of the dams have a curved shape and a slim profile, although some of them were never finished. From an artistic viewpoint, the older dams had some highly fascinating aesthetic features: highly beautiful staggered embankments, ample crests of variable lengths featuring stunning stone parapets, unique staircases providing access to a multitude of water inlets, corner edges for measuring water, etc. The older dams were constructed by true master builders. As for the dam basins, it is common in nearly all the older dams to observe partial cladding with lime mortar and cement. Geological evaluations on the part of engineers were scarce in dam projects, but in Gran Canaria if the ravine bed was permeable it was made waterproof.
The second stage of construction of large dams emerged when a mixture of lime mortar and cement was used to build the thick walls of their main body. As was the case of the older dams, engineers continued to adopt the profile normally used in gravity dams, using its own weight to counteract the push of the water on it. Straight-faced dams started to be built, although curved-faced dams still dominated; old dams such as Las Niñas and Los Hornos were completed; and on the most important ravine in all the Canary Islands the Caidero de la Niña dam was built, with a more modern concept. At the top of the Tamadaba massif the first dam made from loose materials was built, with its dry stone rockfill in the body and hydraulic masonry waterproofing screen (Presa de Tamadaba).
In the 1960s not only were many dams finished with masonry using bastard mortar comprising lime and cement, the work for which had started over previous decades (Presa de Chira), construction also started in 1962 on the Soria arch dam (made of concrete) while the walls of other masonry dams were raised by using only cement mortar and a concrete screen.
Finally, in the 1970s work was finalised on masonry concrete dams with stonework parameters finished off in concrete , such as at Parralillo, Gambuesa or Fataga; the unique raising of El Mulato dam with concrete; some concrete dams, such as El Conde in Amurga and Ariñez dam; and the striking dams of Tirajana and Siberio made from loose material, two recent works of art the result of the collective efforts by dam engineers who let their imagination run away with them as they managed to close off two extraordinary ravines.
It is said that dams are the maximum expression of power, an open book to technical evolution and a mirror image of the relationship of man with nature; and that by contemplating the conjunction of the dam with its surroundings, our minds wonder if all this forms a whole new type of monument. A monument which blurs the distinction made between nature and artifice that emanated from divinity: that which we call a cultural landscape. All the large dams are hydraulic works of high cultural interest. A personal thought.
BY JAIME J. GONZÁLEZ GONZÁLVEZ. GEOGRAPHER
SPANISH VOCAL OF THE INTERNATIONAL COMMISSION ON LARGE DAMS