The only thing that can save the Guadalquivir from widespread flooding are the swamps and the room for maneuver is becoming less and less

Right now, Andalusia has six rivers at red level and many more than 3,000 people evacuated in Cádiz, Jaén, Granada and Málaga. But that’s not the bad news, the bad news is that there are hours and hours of rain ahead. A rain that, according to the data that is beginning to arrive, not even the models have captured well and is exceeding expectations.

That’s what Google saw when it activated the flood risk. What I didn’t see is that the reservoirs can contain the problem. They are, in fact, the last hope of the lower Guadalquivir valley if the situation gets out of hand.

The question is whether they have room to maneuver.

What is lamination? Flood lamination is a hydraulic engineering technique used to reduce the peak flow of a river flood. What is done is to temporarily store water in reservoirs and retention areas in such a way that the amount of water that reaches downstream is controlled.

Although all reservoirs have the capacity to laminate floods (that is, the maximum flow that can leave the reservoir is always less than the maximum flow that can enter), not all have the same capacity to do so. In this case, the truth is that the Guadalquivir basin has many reservoirs and is hyperregulated.

And what does that mean? Well, the SAIH of the Guadalquivir Hydrographic Confederation has been working for days to prepare the basin so that the impacts are minor. For example, the reservoirs in the upper part of the Genial basin (where the largest water discharges are expected this afternoon-night) They have been releasing reserves for days downstream. In the same way, the swamps at the head of the Guadalquivir (especially The Tranco and, to a lesser extent, Siles) are ready to receive water.

The problems are further down, of course: in Seville there is only one reservoir is below 90% and although Iznájar has capacity to laminate the Genil, the situation can quickly get complicated.

How quickly and how complicated? The CHG I said yesterday that “for it to overflow (in Seville) the flow must reach 3000 cubic meters, now it is at 740.” That does not mean that other places, such as Palmar de Troya, do not end up suffering from the flooding of the river; but it does give us a psychological limit of how strong the flood has been and how effective the lamination has been.

The situation, however, is much more complicated. in the Guadalete-Barbate basin. Right now, the accumulation in Grazalema is destroying the forecasts, the reservoirs are full, reaction times are much shorter (because the distance to travel is shorter) and cities like Jerez are currently living in terrible uncertainty.

This week’s lesson. There is something important that we don’t seem to learn well in the terrible DANA from Valencia: that the danger is not always where it rains, that a red warning does not only affect the place where it is declared and that we must be prepared for the weather to surprise us.

Let’s hope that these days we have time for the waters to return to normal.

Image | Manuel

In Xataka | Andalusia anticipates the storm and has already canceled in-person classes and activated the UME. The doubt is placed on the workers