Forecasts for the Elbe

Heat and droughts are more and more frequently producing unusually low water levels in the Elbe, which is also a problem for the port of Hamburg: the lower the water level is, the faster its shipping channels and berths fill up with sediment. Thanks to seasonal forecasts prepared by the Alfred Wegener Institute, the Hamburg Port Authority can now prepare for such developments well in advance – and more effectively plan the necessary landscaping work.

May you always have the proverbial hand's breadth of water under your keel? In the port of Hamburg, that can’t be guaranteed without the use of dredging excavators. After all, not only does the Elbe constantly transport sediment there from its upper reaches; with every high tide, additional material is washed in from the direction of the North Sea. In extreme cases, this can cause the height of the riverbed to rise by several metres in just a few months’ time. If this were to go on unchecked, the port would soon be too shallow to be safely navigated. 

To make sure that doesn’t happen, every year the Hamburg Port Authority dredges several million metric tonnes of sediment from the Elbe. But doing so poses a complex logistical challenge, since the question of where the most material is deposited depends on a range of factors. In this regard, the Elbe’s water level is one important aspect: the lower it is, the more bay mud and sand accumulates in the harbour. Consequently, drought summers – which will become more common as climate change progresses – exacerbate the problem.

As a result, the Port Authority must be able to flexibly respond to changing conditions – and the less advance warning there is before the specially designed excavators are called in, the more expensive it is. 

As such, the Port Authority has a vested interest in knowing what water levels to expect as soon as possible. But until recently, rivers’ water levels could only be reliably forecast a few weeks in advance, at most. At the AWI, we have now developed a technique that allows us to see much farther into the future. With the aid of the new computer models, the Port Authority can now estimate how much dredging work will be sensible and necessary, up to six months in advance. This helps keep the port navigable – and not just more effectively, but also far more economically.