How do rivers keep running for thousands of years?

Question

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

Answer 1

The basin that a river draws from is often quite large. The most extreme example is the mississippi, which drains from about 20 states.

It is all about the fact that rivers drain from incredibly large areas of land.

That water can run down. Look at the colorado river which has had extreme drought for decades and the total flow from the river has been steadily declining over time.