system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does all the water in a manmade lake get there?

Summer is upon us, and I've been at a lake near my house everyday this week. Last night I couldn't help but think about where all that damn water came from?
gpt
A man made lake is not a stock pond. They do not dig a hole and put water in it. A man made lake is created by building a dam on a river and that river no longer being able to flow builds up behind the dam making a lake that grows in size until it either reaches the power intake ports if it is a hydroelectric dam, or it reaches the overflow channels if it is a retaining dam.