The Danube inland delta is a system of main branches, side branches and wetlands, which were originally fed by water from the old Danube riverbe. From the “old” one, because a new inflow channel was created to Gabčíkovo water dam, where most of the Danube’s water is now diverted, and the old (original) Danube no longer communicates with its original branch system, because it is much lower (it lacks water and sediments to reached it). But that’s also what the simulated floods are about, which supply the missing water to this branch system at least twice a year.
And in the branch system – on the main branches – a so-called artificial flooding system was built. linear weirs, which can be fenced off if necessary and in this way handle even lower water flows and pour it into the territory.
So much for the introduction, so that the rest of the text is understandable.
And as part of these dams, the pipe culverts, where the water was brought out below the weir. However, you can imagine how the pipe works in the Danube, when the water is high it gets clogged with the first vegetation and wood.
Therefore, during the restoration of the main branches in the branch system, when they are dug up and cleaned of sediments, we gradually change these pipe culverts to frame culverts. Frame ones, because they are concrete frames, through which water can flow much faster and at higher flows, which will hopefully be more common after testing 120m3/sec. into the branch system, these culverts should be much more efficient and the water that flows through them should be able to wash away sediments and expose the necessary Danube gravel bottom.
Long story short – when you let in a lot of water somewhere, but lower it into a thin pipe that gets clogged, it doesn’t have much of an effect. Especially if you want to control the height of the water level above the pipe and flush the sediments below it.
Well, so if we want to work effectively with the flows in the branch system, restore habitats such as gravel bottoms, improve the passage for fish, but also use the river’s dynamics to, for example, create steep river banks, we must also think about technical structures and their modification in this way.
Well, we are getting to the point – we are looking forward to the fact that we will be able to modify the dam in this way for the second time in three years, and soon (the work on the Vojčianske Ramen will start in about two weeks). The photo of the functional frame culvert is from the Šulianske branch, and the technical documentation, which is already stamped and the field work is awaiting its implementation, is on the attached drawings.
We are looking forward to further work on water revitalisation.
This post is probably also an example of how sometimes nature protection is a complex activity and how even a conservationist can become a bit of a water manager.
Of course, we implement all these modifications in cooperation with real water managers, according to the original study of the renewal of the branch system by the Research Institute of Water Management / VÚVH
Water management construction, state company
We are also preparing this project in cooperation with WWF Slovakia