No. 2 - Its Gran Canaria Magazine

18
GET TO KNOW GRAN CANARIA I CONOCE GRAN CANARIA Nº 2
A brief history of
The construction of large dams in Gran Canaria
BY JAIME J. GONZÁLEZ GONZÁLVEZ. GEOGRAPHER
SPANISH VOCAL OF THE INTERNATIONAL COMMISSION ON LARGE DAMS
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.
▲▼
Presa de Soria. Photos Pepe Dévora
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.