Last week's breaching of the Kakhovka dam in Ukraine will continue to exert a major impact on the populace, on agriculture and on the ecosystem upstream, and not just downstream, of the site, due mainly to the fall in groundwater levels, Professor Jaanus Terasmaa of Tallinn University says.
Appearing on ETV show "Ukraina stuudio", Professor Terasmaa, whose specialty is in eco-hydrology, noted that Ukraine and Russia seem to be placing the blame on each other for the explosion which ruptured the dam, in Kherson oblast.
In any event, the incident was massive and will continue to have major repercussions for many years to come.
To put things into perspective, Tereasmaa pointed out that the volume of water, 18.2 cubic kilometers, which poured through the breach starting early last Tuesday, is almost as much as the volume of water contained in Peipsi järv – Europe's fifth largest lake, and part of a larger system of lakes if one includes Lämmjärv and Pihkva järv to the South.
He added: "If we combine all the reservoirs in the Tallinn water catchment area, plus other lakes and bodies of water there, that converge in Ülemiste järv (water is carried by canals to that lake, in turn used to provide Tallinn's drinking water-ed.) plus Ülemiste järv itself, the volume comes to just 0.076 cubic kilometers, i.e. we are talking about several orders of magnitude difference between that and the flooding in Ukraine."
"The volume of water that has been unleashed from there is mind-boggling," he added.
While in terms of single incidents the impact of the rupture is without precedent, its effects can only be fully assessed retrospectively, he said. "The water delivers debris from one place to another – from one city to the next, while something gets left behind on the road, something gets taken away, something gets moved on again, some of it ends up in the forest or on the streets, while yet more finishes up in the Black Sea."
"This brings two further environmental effects, everywhere. It dumps more detritus, crushes, carries away, washes away topsoil, dumps debris and so on. We're talking about the kind of effect that, when it's all over, you can start looking in retrospect – what do we have left and what has been taken away. Clearly the fallout is major," he went on.
Second, groundwater is affected, and consequently well-water which people use.
In fact, the effects on groundwater is worse upstream, than downstream, Terasmaa said – while the floodwater entering groundwater downstream makes up a small proportion of the whole, the effects downstream on such a large body of water which had been there for decades (the dam was finished in 1956 – ed.) suddenly no longer being present will be far greater.
At the very least this will lead to a fall in the water table.
This happened in Estonia also, albeit peaceably, when water levels at the Sindi reservoir in Pärnu County were reduced, with the result being that nearby residences which used wells saw the water table fall, and in some cases dry up altogether.
It will take another one or two weeks for the reservoir formerly dammed up at Kakhovka to more or less empty, Terasmaa said, which is another more short-term effect. It will take time to get systems up and running.
Additionally comes the risk of disease spread, given that the floodwater includes outflow from water treatment plants, sewers and landfill site.
Again, the impact on the natural ecosystem will be worse upstream, than it is downstream.
"I think there will be rapid, direct impacts this week, next week and maybe the third week in-a-row, followed by a certain time period for recovery; for a little while the soil there will be spoiled, some will be washed away, but nature there will probably do better.
"Upstream, problems are still arriving, as obviously it won't be able to restore the dam any time soon. That will take a matter of years, while the fall in the water table there will likely also create significant impacts on the ecosystem, as well as on agriculture and on the public," he added.
Editor: Andrew Whyte, Merili Nael
Source: 'Ukraina stuudio', interviewer Reimo Sildvee.