The most severe drought in decades has dramatically shrunk Europe’s major rivers. In some places, once mighty waterways like the Loire and Rhine have been reduced to a mere trickle, with their riverbeds laid bare. The Danube, Europe’s second-longest river, is no exception, hurting trade and fishing immensely as ships find it increasingly difficult to navigate the low waters. To make matters worse, the unprecedented drought has exposed a graveyard of sunken WWII German warships near Serbia’s river port town of Prahovo. The wrecks not only hamper navigation but also present threats of explosion as the dozen of sunken ships still have explosives and live ammunition onboard.

War and climate change

More than 20 hulks are now visible stretching over the Serbian side of the Danube, their once menacing canons and turrets peaking out of the water’s surface. But there used to be hundreds of such warships scuttled along the riverbank as Nazi Germany’s Black Fleet retreated in disarray upstream in 1944 as the Soviets closed in from the East.

In September 1944, the warships were deliberately scuttled at the orders of Rear Admiral Paul-Willy Zieb, the highest-ranking officer of Nazi Germany’s navy from 1935 until the end of the war in 1945. Initially, the nearly 200 cruisers, destroyers, and torpedo boats that operated in the Black Sea during the war were meant to retreat upstream all the way to Germany, but the fleet came under heavy artillery fire from the Danube’s shore and from air strikes. A desperate decision was quickly made to scuttle all the boats in a zig-zag pattern such that any Soviet advances up the river would be hampered. The sailors were ordered to march on foot all the way to the Serbian capital of Belgrade, which at the time was still under Nazi control.

It’s unclear how much time this move bought Nazi Germany, whose days were numbered by that time. What history is more clear though is that in the ensuing 80 years, the scuttled boats have caused all sorts of havoc in the area. Millions were invested to clear away the wrecks, but many still remain at the bottom of the Danube.

“The German flotilla has left behind a big ecological disaster that threatens us, people of Prahovo,” Velimir Trajilovic, 74, a  resident of the Serbian port city, told Reuters.

Europe’s ongoing mega-drought, which may very well be the worst in 500 years, is now showing that you can’t sweep problems under the rug (or under the water) forever. Driven by climate change, an usually dry winter, record-breaking heatwaves, and virtually no rainfall in sight for the past two months, the Danube’s levels are at an all-time low. So much so that Serbian, Romanian, and Bulgarian authorities have dredged their sides of the river to carve deeper channels and allow a semblance of navigation. Shipping costs have surged due to ships having to operate at a fraction of their capacity to reduce their draft.

The problem is now compounded by the abandoned hulks, which have narrowed the navigable section at Prahovo to just 100 meters (330 feet) from 180 meters. Elsewhere, in Italy along the now dried river Po, authorities have found WWII relics of their own, including an unexploded 1,000-pound bomb and a 50-foot barge.

According to the Serbian government, the cost of removing all the hulks, ammunition, and explosives from Prahovo is estimated to run at 29 million euros ($30 million). It’s too late to salvage this season, but the current drought has taught everyone that the Nazi warships will have to find a new graveyard — and soon — such that situations like these don’t happen again.