Rivers are more important to the water cycle than streams.

Rivers are the most important part of the water cycle because they collect water from precipitation and directly move it back into the ocean. As this happens, rivers deposit sediments into the ocean that brings about different formations of lands. They act as drainage systems for other bodies of water that are found inland.  

Aside from transporting water back to the ocean, rivers are good habitats and food sources for many organisms. Humans are also dependent on rivers. Most early towns were built around rivers because they accommodated the growing industry of trade and human civilization as we know it.