Complex sentence: The term "sinking" is more accurate then "seeping", because, instead of just distributing into the soil, the Danube's water flows through underground caverns to the Aachtopf, where it emerges as the river Radolfzeller Aach.
Split into simpler sentences: The term "sinking" is more accurate then "seeping", because the water is not easily distributed in the soil. It flows through underground caverns to Aachtopf, where it emerges as the river Radolfzeller Aach.