Hello Anti-Valentine. A quick answer is if the water is soft or hard regarding the content of minerals. Ponder those who have water softeners and those who live in area with high mineral content. Just sharing I remember in West Virginia bathing with water with a high sulfur content. I don't remember the affect of the soap lather, yet I do remember the effect of the smell + giggle.
Consider rain and the watershed principal regarding the source of the water. For instance here where I live in Escondido there is a reservoir for emergencies more or less, so not an everyday source for water. Our water is piped in from the Colorado river, which is a long way away from here. So, the advent of rain, the watershed principal, the time to pipe the water, and its arrival through the shower head is a product of time with the flow of events.
The water changes at the source and what ever occurs at a water processing plant. Along the coast and on board ships there is a high content of salt, even though there is a desalination process. So the water if'n I remember correctly is harder with the content of salt. Note: With water softeners there is consideration of reverse osmosis.
Now, the fun part is you have an opportunity through discovery of more answers to compare and contrast while seeking whether or not a hub answers or you as an author write something with its regard or just Google for more info. My hope is this at least offers a little bit more than the before seeking only a bit of pondering.
Remember to smile, which I believe you do, and have fun, fun, fun . . .