Final answer:
The Kremenchuk, Kashovka, and Kiev Reservoirs are all located on the Dnieper River, an important waterway in Ukraine and historically significant in the Kievan Rus' region.
Step-by-step explanation:
The river that has the Kremenchuk, Kashovka, and Kiev Reservoirs is the Dnieper River. Located in Eastern Europe, specifically in Ukraine, this river plays an important role in the historical region known as Kievan Rus'. Its significance is also highlighted by the presence of a monument to prince Vladimir I, which overlooks the Dnieper in Kiev.
This river is essential for trade, transportation, and water supply in the region, linking the Baltic Sea with the Black Sea, and has been a historic link with wealthier regions such as the Byzantine Empire.