Ancient ominous warnings carved on usually submerged boulders along the Elbe River had for centuries driven fear into the hearts of Czechs, but their reappearance during this year's drought is just a reminder of how tough people had it.

The so-called Hunger Stones can only be seen above the water surface during droughts, and used to presage bad harvests, interrupted river navigation and consequent famine. Now, the messages appear weeks after weather and crop forecasts.

In Decin, just over 100 km (60 miles) north of Prague and not far from the German border, a boulder that is Central Europe's oldest hydrological marker is fully exposed after the water level in the river dropped to 115 cm.