To my understanding, a river’s source is fueled by snow and rain, but is it enough to keep it running for that long? Afterall the source doesn’t get rain/snow 24/7 so wouldn’t bigger rivers drain the source in a matter of weeks instead of many hundreds of years?
In: Planetary Science
Bigger rivers are FED by larger areas.
For example, the Mississippi River? The giant river down the middle of the USA, it’s basin covers over 1/3rd of the USA (and extends slightly into Canada)
Meaning ALL the rain from Pittsburgh Pennsylvania all the way to Colorado and Montana will eventually drain down through the Mississippi.
And that draining takes time. It doesn’t just instantly rush into the rivers, there are tiny creeks, streams, smaller tributaries that gradually bring the water in. And then there’s also MILLIONS of ponds and lakes and beaver dams that slow the flow of the water down while it gets there.
Plus, a lot of the water doesn’t even go straight into the creeks and streams, it lands on the dirt, is absorbed by the dirt/ground, and then gradually over weeks or months flows through the soil itself. Which also slows it way down.
And yes, during times of drought even giant rivers can get shallower, and during very wet times they can overflow their normal riverbanks.
But generally speaking, there’s so much water over such a wide area of land that it all is just gradually making its way down to the Mississippi, and eventually the Gulf of Mexico. Keeping the river fed.
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