Like a duck to water - how do mallards find water sources with their ducklings?

Hello, I'm hoping someone will be able to help me as I have Googled and Googled to no avail! Once a mallard's eggs have hatched and the ducklings are ready to leave the nest, how does she sense where a good water source is if she's had to nest further from one than she would have liked? Obviously she needs to walk with her ducklings rather than fly so how does she find a river/pond/lake if she's a couple of miles from one and can't rely on spotting landmarks etc?