system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are lakes rich in nitrates?

If it’s due to hills, how are the nitrates moved from the hill to the lakes?
gpt
Lakes are a natural collection point for water, and anything that the water happens to wash over during its journey.  Rain gets into the ground and dissolves nitrates into itself, then washes into streams which wind up in lakes.