The greater presence of rain due to the El Niño phenomenon continues in force over the country and various areas suffer its consequences more than others. In the case of the Uruguay River, it had a spring with three flood waves, a fact that was unprecedented, and a significant rebound is expected towards autumn.
The intensity of these events increases as a result of climate change, so specialists emphasize that we will have to get used to these conditions of variability in which, taking last year as an example, the country began with a significant drought and ended up flooding in several places. .
Read also: Concordia: more than 400 families were evacuated due to the intense rains and the flooding of the Uruguay River
Due to the direct effects of El Niño, the flow of the Uruguay River broke several records: it was the largest November since there were records in that watercourse (1902) and the same month was the largest compared to any other month in recent years. 42 years.
The record breaks do not end there, since both September and October also had records for those months and were the largest since 1981.
In the towns that are upstream from the Salto Grande dam, all people evacuated, since as the head of Hydrology of the Hydroelectric Complex, Guillermo Collazos, detailed to TN, “it rained in more than half of the basin around 500 millimeters more than average record.”
Around 500 millimeters more fell in the flow of the Uruguay River than the average record. (Photo: Télam)
“The Salto Grande dam attenuates the peaks of the floods so that, downstream, the levels reached by the river are lower,” explained the specialist, and as an example he cited that in Concordia “thanks to the attenuation of the dam, the River level was 1.60 meters lower than it would have been” if that containment did not exist.
“2023 was more intense due to global warming, which increases the variability of the El Niño and La Niña phenomena. We had two floods in spring and one of them had three flood waves, something that never happened,” she explained. This phenomenon is about the peaks that a flood reaches within the same event: a maximum value and then decreases.
The flood was different from what normally happens. Since the Salto Grande dam has been in place, “two or three floods with two waves” have been recorded, said Collazos. The one that occurred in spring was unprecedented and more intense.
“The three-wave flood was very long for the people. It was 55 days, almost two months of flooding,” he considered.
The work during the drought was “challenging,” as Collazos recalled: “The summer 2022 (drought) occurs once every 80 years, as we calculate. In 2023, in January we had an average flow of less than 600 cubic meters per second (m3/s) and in November it went to 22,900 m3/s. In January there is a drought and in November there is a very rare and very unlikely flood.”
For Juan Borús, deputy manager of Hydrological Warning Systems of the National Water Institute (INA), “the situation of the Uruguay River has oddities, like everything we are experiencing. We have to get used to this permanently.”
“It began to be striking at the end of August, when an unusually concentrated climatic trend was proposed in the Uruguay River basin for September, October and November. Never before has a more concrete trend been seen than this,” he said, in dialogue with TN.
Concordia, in Entre Ríos, one of the main areas affected by the flooding of the Uruguay River (Photo: Télam)
The specialist indicated that after the third flood a slow decrease in the river level was expected, but that this drop materialized in records that are higher than those expected for the Salto Grande area.
And even though the situation is relatively calm, he stressed that significant rains could occur in the region “because the humidity is there, it is not going to go away”: “It is to be expected that a Niño like this, which was strong at the end December, have a rebound. Watching previous Children, you have to be attentive because, sometimes, what happened in the fall was more important than what happened in the spring.”
In its quarterly climate forecast for January, February and March, the National Meteorological Service (SMN) foresees a greater than 50% probability of higher than normal rainfall developing in the Uruguay River basin.
Collazos stressed that “such a sudden transition is not so common,” from a period of marked drought to the present, and that these more intense variations derive from climate change: “The temperature is higher and the energy that is present gradually increases.” in the atmosphere. The transition is faster from one model to another and what the models predict is that the variations are going to be more abrupt.”
“This variability in short periods is being observed in longer-term phenomena. This also has to do with the anthropic action (of humans) on the basins, where the effects of the hand of man make climatic extremes impact much more on a territory,” he expressed, adding: “If one compares the basin today compared to 70 years ago, there were forests and everything was not so waterproof. “Now it’s all agriculture, with hard soil.”
Meanwhile, Borús contributed: “Both in frequency and intensity, El Niño and La Niña are more marked than before by climate change. 2023 had a certain resemblance to 2009, both years began with very low levels in the large rivers of the Plata Basin and ended with flood levels. “That type of thing is what we have to get used to and that variability is the most obvious manifestation of climate change.”