Just watch as the leaves on the carrot go up and down. The carrot stem - or leaves float depending on how much water is on the pot. You can leave your plant or plants for a few days without worrying whether it will run out of water.
Just place the carrot in the pot and top up with water!
I go away with work for a few days every week or so, this makes sure my plants dont dry out in the warmer months so works very well and look good