The Upper Danube, which includes Alpine headwater catchments (e.g., Inn, Isar, Enns, Mur), is often considered Europe’s main water reservoir with its snowmelt-dependent runoff regimes; large hydropower potential; and unique biodiversity across southern Germany, Austria, parts of Switzerland, and the Czech Republic. The upper headwaters are rather pristine, often fed from glacial outflows in national parks and conservation areas and subject to substantial gradients. However, most Alpine rivers become heavily regulated shortly thereafter because of transport, settlement, and agricultural spatial needs in combination with the exploitation of hydropower potential. Consequently, environmental water supply, flood potential, sediment transport, and downstream flow regimes are altered. Local conflicts involve hydropower, agriculture, environmental protection, and tourism interests.