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Intervija ar LTV laika ziņu redaktoru Tomu Brici

Jēkabpils floods 'unprecedented', says LTV weatherman

The floods experienced along the banks of the River Dauagava in the city of Jēkabpils in recent days are "unprecedented in Latvia" according to Latvian Televsion weatherman Toms Bricis. 

Such a bold statement may seem questionable given the fact that in 1981 the water level was in fact another five centimeters higher. But what merits the "unprecedented" tag are the processes that caused the flooding, which are notably different to the spring floods that are expected every year.

This time aroud the flooding is occuring long before springtime arrives. Unlike traditional spring floods, these ones are not caused by melting snow and ice alone, but also a highly variable temperature regime, which has never happened in winters in Latvia before, combined with high rainfall. 

"In the Daugava basin from mid-November to mid-December there was a stable frost, the river froze over, a thick snow cover formed, which almost completely melted shortly before Christmas, which was followed by frost again, increasing the amount of ice in the Daugava, but this flood wheel began to turn with an unprecedented thaw at the turn of the year, when it rained for several days and the temperature reached +10 degrees Celsius," explains Bricis.

The ice began to move and form jams in the river, which has several hydroelectric stations and dams along its length. This has also happened in other years, when the ice melts in winter, but mostly it is stopped by the return of a stable freeze, the water inflow into the river decreases, the ice jams freeze, and the water finds a way to flow through cracks in the ice and under it. But this time around the re-freeze was too weak. It did not freeze the river shut and return to stability, but only created new ice floes and pieces of ice that continued to accumulate. At first near Pļaviņas and Zeļki, the ice dam became longer and longer, reaching as far upstream as Jēkabpilis.

Compared to the last big flood in 2013, the flow of water into the River Daugava was actually only half as much. There was less water, but crucially, it could not run flow away downstream due to the ice. That's the big difference from spring, when the ice is steadily melting and loosening any congestion. Now, the temperature hovering around zero is not enough to melt everything, and it may continue this way until the real spring comes.

"On social networks, there are calls to open the floodgates of Pļaviņas hydroelectric power plant. But in this case it wouldn't help. If you look at the cross-section of the Daugava River, it is obvious that the level of the Pļaviņas reservoir is already more than 10 meters lower than the water level in Jēkabpils. The reservoir is so low that it does not prevent the water from flowing out. While we usually think of an ice jam as being horizontal, it's actually slanted, much like a river itself that flows downhill," says Bricis.

"If the water level were to decrease, it would even reduce the chances of the ice jam breaking up, because the water level at the front of this ice jam, or as hydrologists call it, the head, would decrease."

On Sunday, January 15, the water level started to drop in the Daugava at Jēkabpils. In the spring, it would usually mean the end of the flood and allow everyone to breathe easy, but this time again, things are not so simple.

The water level upstream from Jēkabpils continues to rise. Jēkabpils is on low ground. One part of the city is protected by a dam, but further up the river there is no protective dam. Water began to flow into the city along the part of the bank that is not protected by the levee. Thus, water flows into the city, allowing the level of the river itself to drop, but the drop in water level does not mean that the flood will decrease, the water has simply found another way to reach the city and the surrounding countryside. At the same time, of course, it allows us to hope that the existing river defenses will withstand the pressure they are subjected to, preventing a sudden mass of water and ice to rush into the city with great force.

The water level in the Daugava tributaries has started to rise. The thaw, however, is far too weak to break the ice jam, and it is clear that it will not completely break up. Next weekend, a more significant freeze is expected, which will again produce slush and ice, but will be too weak to fully freeze the river and calm the waters.

"It is thought that the waters will completely recede from the floodplains and the lowest places no earlier than March, but it is impossible to predict how the ice jam will behave in the future, which will depend on whether there will be a dangerous rise in the water level. Hydrologists indicate that a great risk remains at Pļaviņas, because when the weather gets warmer and the ice jam moves, water masses from Jēkabpils will get there very quickly. So, although the situation can be described as critical but stable for the time being, there is no certainty about stability in the future.

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