Why does the middle Danube River have high-water peaks in April and June?

The middle section of the Danube River experiences two distinct high-water peaks in April and June due to different hydrological sources:1

• June Peak: This high-water period is primarily driven by the upper course of the river. It results from the intensive melting of snow and ice in the Alps, with the peak reaching the middle basin 10 to 15 days after it occurs in the upper reaches.1
• April Peak: This is a local phenomenon caused by the combination of melting snow in the surrounding plains and early spring rainfall across the lowlands and low mountains of the middle basin area.1

These peaks reflect the complex hydrology of the river, as its basin spans diverse climatic regions.12