To explain further, what stops lakes from simply seeping into the dirt, and thus vanishing? As a follow up question, what stops water from getting evaporated, and then the clouds move somewhere else and rain, thus depriving the lake of the water it lost?
In: Earth Science
There are some great answers here. I’m going to try to break it down a bit for you.
It’s pretty obvious that water flows downhill. It might not be as easy to see but water flows downhill where you can’t see it too.
Imagine you are at the beach. A common fun game is building a sand castle. Every castle needs a moat, right? So you dig down, and boom… you strike water! You found the water table, or water level.
The water table at the beach is *very* nearly the same as ocean level (or lake level if you are at a beach on the lake… **spoilers**). If you go further and further from the beach the land elevation generally increases. But the water table generally increases too! At least near stream, rivers, and lakes. So if you are in an imaginary house, digging an imaginary well, *near* a stream, then the well will be pretty shallow. If your imaginary house is *far* from an imaginary stream, the imaginary well will be deep. Don’t be fooled by soil, clay, or rock. They all hold bunches of water in different ways.
Here’s the thing if your imaginary well was a few feet/meters closer to the stream, at the same height, your well would be correspondingly deeper. The water, underground, is flowing downhill!
A lake (sea or ocean) is temporary place where the surface ground is lower than the water level. Most of the time a lake is like a hidden waterfall moving water over the “edge” in slow motion and hidden from view.
There can be exceptions due to spring fed lakes. They can be *higher* than local water table because the spring that feeds them is from an artificially higher water table. Central Florida USA is famous for them. Water from “high up” in Georgia gets trapped beneath impermeable ground and is kind of under pressure. It’s positively asking to get out and up. As it flows “downhill” to flat old Florida it finally pops out, making lakes and rivers galore.
Lastly all lakes (seas or oceans) are geologically temporary things. Lakes silt up into marshes really “quickly”. Seas too. Oceans open and close all the dang time (geologically speaking). In current news there is a volcano in Iceland going bonkers. That volcano is on the Mid-Atlantic-Rift. A place where the ocean floor is **spreading** and making the ocean bigger. Other times it gets smaller, even till it has disappeared altogether.
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