“I was built on water, my walls are of fire, this is my insignia and my blazon.” This is how the legend of what was probably the first emblem of Madridback in the XII century. Without a doubt, a good introduction to take the pulse of the situation of the quality and quantity of water in the Community of Madrid. And more so in this summer of high temperatures, when many are looking at the reserves of the reservoirs in the region. However, some studies on these same waters in Spain are another matter. They point out that Nearly half of the groundwater bodies in Spain (specifically, 44%) is in poor condition, which represents a surface area of more than 140,000 square kilometres.
Reports analyse the 804 recognised groundwater bodies in Spain, of which 353 are in poor condition and cover an area of over 140,000 square kilometres, that is, almost 40% of the surface area occupied by all the bodies. This situation occurs mainly in the southeastern half of the peninsula, but also in the Northern Plateau, the Balearic Islands and the Canary Islands.
As if it were a Gallic village… not all is lost. In Madrid, beneath the city, lies an enormous aquifer of 2,600 square kilometres formed between 23 and 5 million years ago. It is the Tertiary detrital aquiferwhich can reach depths of almost 3,000 meters: the first 800 are exploitable for use in supply.
Geologically speaking, the permeability of the land where it sits is very low, however, that does not prevent it from being able to recharge naturally due to the infiltration of the rain water: It has an annual recharge capacity of about 120-150 cubic hectometres. It is surprising to learn that part of the waters that are still stored at great depth today They were able to filter through thousands of years ago, so talking about “large reserve” water would be an understatement.
Despite its greater conductivity, the waters of the Tertiary detrital aquifer are of weak mineralization and meet the parameters required for the human consumption. Every year, in addition, Canal de Isabel II We carry out a groundwater sampling campaign to ensure that its quality remains optimal.
In addition to the detrital Tertiary, under the zone of Torrelaguna another mass of underground water settles: it is the Cretaceous carbonate aquifermuch smaller and with waters of different quality, although also recharged thanks to the infiltration of rain and streams. This second outcrop has an area of 56 square kilometers.
The presence of these groundwaters under Madrid and their incorporation into the supply system of the Community represent a great relief in terms of water management, since it allows for a greater volume to be available with which to deal with periods of drought or contingency situations.
More than 80 wells
There is also a network of more than 80 wellssome of them up to 800 meters deep, which have powerful submersible pumps, located at an average depth of 300 meters.
In reality, since they are reserved for periods of emergency, groundwater usually remains quiet, with little importance, until it is needed. Then, its contribution to supplying the population becomes decisive. This was the case between the years 2005 and 2006moment of the last great drought that devastated Madrid, leaving our reservoirs at critical levels below the 40 %. In this situation, the extraction of groundwater served to alleviate the shortage of stored water.
Hidden from our eyes, in short, we can consider the aquifers of the region as our fourteenth reservoir.