original: The Arkansas River is a major tributary of the Mississippi River.
simplifications: The Arkansas River makes up the big part of the Mississippi River. The Arkansas River has big merger into the Mississippi River. The Arkansas River is a major part of the Mississippi River. The Arkansas River is an important tributary of the Mississippi River. The Arkansas River is a big tributary of the Mississippi River. The Arkansas River provides a lot of water to the Mississippi River. The Arkansas River flows into the Mississippi River. The Arkansas River is a main tributary of the Mississippi River. The Arkansas River is a major tributary of the Mississippi River. A tributary is a river that flows into a larger river or lake. The Arkansas River flows into the Mississippi River.