system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do rivers flow continuously?

I understand the water cycle in that water is evaporated, condenses, and precipitates which puts water back into the ecosystem, but how does a river continuously flow millions of gallons of water when it eventually empties into an ocean? Where does all the water come from to keep it going nonstop?
gpt
The water in a river comes from many different sources.  Let's try to think of a few.  There are springs, where the water bubbles out of the ground.  There is rain, where the water precipitates, or falls from the sky.  There is the melting of glaciers or snow cover.  The water also seeps out of wet ground, and the water we pump out of the ground for use in our homes and businesses probably gets treated and then put back into the ecosystem, where it flows into rivers.  

The watershed, or area in which the water will flow to a particular body of water, is quite large for most rivers.  All of these sources combine over that large area, to form the river.  Rivers naturally rise and fall over time, as the amount of water flowing in changes with seasons and weather.