"Are you kidding? 1 litre of water weighs one kilo! A pound 4 ounces is nothing!"

It's not either or though is it? You are carrying heavy water and the thing required to take it at source, and you are pumping it also. It's a lot of work just to avoid tap water. Now if the water suppply is uncertain, you probably need a few options, and a pump might have to be one of them.