The largest waterfall by flow rate: Inga Falls
Another way to measure the size of a waterfall is by flow rate, or how much water rushes over the edge of the falls, regardless of the height of the drop. For this category, Inga Falls in the Democratic Republic of Congo is the clear winner. This waterfall is a cascade that drops 315 feet over the course of 9 miles on the Congo River. Water rushes down Inga falls at the rate of 910,000 cubic feet per second! For comparison, Niagara Falls (the largest waterfall in North America) gets just 85,000 cubic feet per second.
Lest you think this is a set of rapids and not a true waterfall, it is indeed a fully fledged waterfall, with one section dropping a full 70 feet. The World Waterfall Database states, "Many, if
not most accounts seem to discount it as nothing but rapids but we
suspect that the most substantial portion of the falls are actually
quite steep and can be legitimately considered to be a true waterfall..."