It’s important to remember, dirt isn’t a normal. It’s organic, created by living things that broke down rock. So if you go down far enough you get rock. Water eroding away at certain rocks creates things like clay, which you can think of as dust that clings to water. Clay doesn’t really flow and so isn’t likely to sink much lower, it’s taken on as much water as it can and so the water above doesn’t move into the ground as quickly as it would through porous rock or soil. It sets up a situation where you’re likely to have as much if not more water coming in as it leaving.
As for evaporation not just drying up any given lake, they are usually at a low point in the surrounding area, meaning it doesn’t have rain directly on the lake to regain the water it loses to evaporation. Of course lakes do evaporate sometimes, but as lake gets deeper it’s going to have less surface area to lose water from compared to the total volume of water.
Both of these things are happening constantly, but the rate at which they happen (overall) is not fast enough to make the lake be empty =)
For water to seep into the dirt it has to have somewhere to go. The dirt at the bottom of the lake is already saturated, so it can’t absorb more water. Usually you have to go pretty far away to find soil that can hold a lot more water for the exact reason you asked about.
Likewise, water is constantly evaporating from the lake. But a lake only has so much surface area so it can only evaporate so fast.
In contrast, lakes are typically areas where lots of rivers/streams/runoff feeds into a single location (the lake), so they are constantly refilling.
Under the bottom of the lake is a layer of impermeable rock. Otherwise it does leak into the ground, forming an aquifer, and leaving a dry lake bed in it’s wake.
The rate of recharge is also pretty close to the rate of evaporation in many cases; when it’s greater than evaporation rates, it overflows causing flooding, when it is less than evaporation rates, the water levels in the lake start to drop.
The hydrologic cycle is a good place to start looking to satisfy your curiosity
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