Drought: how the salt wedge phenomenon is destroying the Po’s river ecosystem and threatening agriculture
The warning from the Land Reclamation Consortia: river flows at record lows are facilitating the backflow of seawater along the rivers, causing damage to the river ecosystem and agricultural production
Key points
For centuries – almost certainly millennia – it has been the waters of lakes and rivers that have flowed into the sea. In an era of climate change and, above all, of prolonged drought, rivers are losing their strength and flow, and the direction of the water is reversing. And it is the sea, and the salt water, that now flows upstream along the rivers. In recent years, there have already been many warnings have been issued regarding the so-called ‘salt wedge’, that is, the phenomenon whereby seawater flows upstream along the rivers. A warning that rings out even louder this summer of 2026.
The sea has flooded the Porto Tolle area in the Po Delta
It is ANBI, the National Association of Land Reclamation Consortia, that has issued a veritable ‘environmental war bulletin’, stating that ‘The salt wedge now surrounds the Porto Tolle area, forcing the Po Delta Land Reclamation Consortium to close all irrigation channels’.
The flow rate of the River Po – as ANBI further explains – after having recorded its lowest level of this difficult, drought-stricken summer, is set to fall well below the psychological threshold of 200 cubic metres per second (the minimum threshold for combating saltwater intrusion is set at 450 cubic metres per second).
The rainfall forecast for the Alps could help
The Permanent Observatory for the River Po can only note that the situation has worsened compared with last week, when the alert level had already been raised to its highest level. Some relief – as ANBI further explains – could come from rainfall across the Alps, but with hydroelectric reservoirs depleted and upstream withdrawals reduced, current flow rates are sustained solely by water returned from irrigation systems.
This, however, is not enough to give the Polesine and the Delta some breathing space, as their coastline has effectively retreated at least 20 kilometres inland, invaded by saltwater intrusion. And the salt profoundly alters the river ecosystem, damaging the flora and fauna and, in the not-too-distant future, posing a serious threat to agricultural activities.
