Final answer:
The Amazon River accounts for about 20% of all river flow in the world, with extensive tributaries and unmatched discharge, carrying a vast amount of the world's river water.
Step-by-step explanation:
The river that accounts for about 20% of all the river flow in the world is the Amazon River. This mighty river is more than 2,000 miles long and has an extensive drainage basin in the world's largest tropical rainforest. The Amazon River has many tributaries, each larger than many of the world's rivers.
Additionally, with its equator-parallel flow, the Amazon is a contender for the longest river in the world, rivaling the Nile River. Of particular note, the Amazon's discharge is unmatched, carrying approximately one-fifth of the world's river water, highlighting its significance not only in South America but as a critical component of the global freshwater system.