Drought has been one of the recurring themes of recent years. Both the lack of rains and their diverse consequences have more than a five years in the informative agenda. That is why the question of how much water we have left has asked Very diverse ways.
There is only one problem: we are not really able to answer it.
Moreover, what we know that our water reserves They are usually below what the data indicates. The reason is in something as natural as erosion and sedimentation processes, but its consequences They have been worrying the experts for years.
Throughout their channel the rivers transport small particles of rock and organic matter that tend to accumulate at certain points of the route, either on the river bed, in river deltas or in its meanders. The reservoirs are another of the auspicious places in which the water tends to “release” these particles.
The swamp floor Thus tends to accumulate sludge. The first problem that this generates is the loss of swamp capacity. The higher the volume of this occupied by sediments less is the amount of water it can store.
The second problem is that we do not know exactly how the sediments accumulate in each swamp since it can vary depending on the characteristics of each basin and each reservoir. If we don’t know how many sediments we have, we can’t be sure how much water we have left.
The weight of the terrams
Estimates on the weight of the terrain, which is how this accumulation of sediments is known in the reservoirs, vary. A Batimetry Study made in 2018 For the Tajo Hydrographic Confederation in the Entrepeñas and Buendía reservoirs, he estimated that the accumulation of these sediments was insignificant.
At the opposite end, Another batimetry studyis made by the Segura Hydrographic Confederation, estimated that its reservoirs could have lost between 10 and 40% of its capacity due to the incidence of this phenomenon. They highlighted the case of the Lorca reservoir, built at the end of the 19th century, which would be at the upper end of this fork.
Estimates made for the whole Spanish reservoirs are limited. A study conducted from 110 reservoirs estimated that The loss of capacity could be around 5%. José Luis Casamor and Antoni Calafat, from the University of Barcelona, They warned in 2018 that uncertainty was high in this estimate, since the possibility of extrapolating the results of this study to more than a thousand remaining reservoirs was limited.
This is a problem on which experts carry years warning. The study carried out in the Segura Basin, for example, was carried out in 2017, while Casamor and Calafat’s work was published in 2018 in the publication Earth and technology of the ICOG (Illustrious Official College of Geologists).
In a second article (also published in 2018) in The conversationCasamor explained that that of terraces was a problem with “faces and difficult execution” solutions “. Cleaning the sediment reservoir bed is an arduous task that requires the emptying of the reservoir, something that can be even more complicated in old reservoirs, explains Casamor.
Prevention is a better option for this expert. This is to incorporate knowledge about the accumulation of sediments in the infrastructure design process. Another inclusion of dikes prior to the reservoir may contain the sediments up so that they do not accumulate in the reservoir.
Other proposed measures to contain the sediments upstream include reforestation. The plants contain the erosion of the soil, which makes less particles reach the rivers and from there to the reservoirs. In this sense, rural abandonment has also been indicated as partial responsible for the situation. The fires also contribute to the arrival of sediments to the channels, so the fight to contain them can also contribute their grain of sand.
Image | Ray Raimundo
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