The dana, “of extraordinary power”, reduces the rain deficit in Spain by four percentage points

What effects the dana has had on the battered swamps of the drought after a dry and hot summer is the big question that many ask when seeing the magnitude of the water that fell in Spain in just three days. The answer to this question is, for the moment, disappointing. The Ministry of Ecological Transition published the weekly reservoir water bulletin this Tuesday and the level has dropped, although only very slightly. The water reserve has fallen by 0.6% – 319 cubic hectometers less – and the reservoirs are today at 37% of their capacity, with 20,763 hectometers. In reality, it is still early to gauge its impact.

In the note, the ministry explains that “the pluviometric contributions of the dana are not yet noticeable in the reserves, given that at the close of the bulletin the volumes of water are increasing the water reserves in the soil and in transit through the channels towards the reservoirs.” That is to say, in a country at the end of summer, with the land so dry and in a situation of long-lasting meteorological drought since last December, the first thing the land does is act like a sponge and then, whatever is left, is will redirect to the reservoirs. Thus, these do not yet include the “pluviometric contributions of the dana”. Despite the decrease, the reservoirs accumulate 1,092 cubic hectometers more than a year ago, although they are 8,250 below the average of the last 10 years. The most worrying are those of Guadalete-Barbate (16.8%) and Guadalquivir (19.3%).

However, these rains, in many cases of torrential intensity, have already improved the year’s water balance, reports Rubén del Campo, spokesperson for the State Meteorological Agency (Aemet). On August 29, the rainfall deficit compared to what it usually rains in Spain as a whole was 17% and, according to the latest available data, on September 3 – on Monday it rained a little more with the last blows of the dana – It was 13%. A 4% reduction in five days. “The lack of rain has been partially alleviated and, when that water reaches the reservoirs, we will see next week if the dammed water really increases,” says Del Campo.

In a first summary of what happened, the Aemet spokesperson highlights that the damage caused torrential rains, especially in parts of the Mediterranean. It also rained a lot in the northeast of the Peninsula on Saturday, which was the most adverse day in the Navarra area and the Aragonese Pyrenees. Then it moved and on Sunday it especially affected, as had been announced, the center of the Peninsula.

“It is significant that, for example, in the Tagus accumulation basin – the Aemet basins are similar to the hydrographic basins but do not coincide exactly with them – in those five days an average of 61 liters per square meter have fallen when the average in one week is five. It has rained 12 times more and almost all of it in one day, Sunday. In the Duero and Guadalquivir, seven times more, in the Guadiana, nine, and in the Júcar, Segura and Ebro, between four and five,” the meteorologist emphasizes.

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As for records, on Sunday, there were three absolutes in Aemet’s main stations, that is, it was the rainiest day since there are records. They were those of Segovia (50 liters), Toledo (90) and Valladolid (60). On Saturday, Pamplona broke its monthly record for September with 62 liters. “At stations on other networks there have also been very significant records,” he adds.

List of records broken with yesterday’s storms. In capitals, the daily precipitation for the month of September stands out in Valladolid (60.4mm), Toledo (90.4mm) and Segovia (50.2mm).

Also that of Toledo of wind reached during the most intense storm (105 km/h) pic.twitter.com/Ww69bTK5Ee

— Víctor M. González (@gdvictorm) September 4, 2023

In a first analysis, Del Campo points out that this episode stands out, but not because it is premature. “We have had floods before in recent years, such as the one in August 2017. Two years ago, on September 1, 2021, there was one that also caused flooding in the province of Toledo. It is not extraordinary that a dana forms at the beginning of September, but it is extraordinary that it was so deep, so powerful, more typical of mid-autumn than the beginning of the season in terms of its dynamic characteristics,” he explains.

This dana also stands out because it has caused a much more widespread and intense storm than its predecessors on the same dates. The amount of precipitation that it has left, in many record points, is probably due to the fact that it was doped, more loaded with humidity than normal, due to “a warmer than normal Mediterranean and, although this must be analyzed in depth , it is possible that it also received contributions from the Atlantic and other factors.”

Another factor that has contributed to the rains being so abundant and persistent in the Community of Madrid and in the provinces of Toledo, Segovia and Valladolid is that “the dana was static on Sunday in the west of the Peninsula” due to a powerful ridge. in the Mediterranean that prevented it from moving eastward. “In general the danas move, but in this case it was static for many hours,” he adds.

Are they going further? “With all reservations, as we always say when we talk about intense rainfall associated with climate change, in which the relationship is not as confirmed as with temperature, what the projections tell us is that we are heading towards situations of more intense droughts and interrupted by episodes of torrential rains that are also more intense. What we are observing fits with what the climate projections tell us,” concludes Del Campo.

Regarding the controversy over whether Aemet was right or wrong when it came to decreeing a red notice in Madrid, Del Campo affirms that the organization is “very aware of the repercussions that these have at all levels,” so, when This decision is made, it is done “in the most reasoned and considered way possible.” “When a red notice is activated, there is a very high probability, 70% in this case, that an extreme phenomenon will occur that can cause catastrophic damage, as has been the case, with five dead and three missing and considerable material damage. ”, he continues. Fortunately for the capital, “the line of storms was a few dozen kilometers to the west, as some minority scenarios predicted. But the probability that it would occur over a large metropolitan area of ​​7.3 million inhabitants and in full operation was real and very high, so the red notice had to be activated.” “The red is more than justified and so is the Civil Protection alert, based on our warnings,” concludes the expert.

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