There are a few different theories as to why your cat may prefer to drink from running water as opposed to still water from a bowl. Cats do not need to drink as much water directly, as unlike dogs their kidneys are highly efficient and can often take enough water from their diet. All domestic cats are descended from desert-dwelling cats that were designed to survive on little water if necessary.
It’s more natural
In the wild animals prefer to drink from running stream or river water than stagnant water. Stagnant water is water that has been sitting in one spot for long periods of time; this water can become dirty quite quickly and is much more likely to harbour bacteria and parasites.
It tastes better
Running water is usually cooler and more oxygenated than sitting water, it also won’t harbour as many particles that could sit at the bottom of a bowl and give the water a bad taste. It is best to re-fill you cats bowl as often as possible as cats are quite sensitive to taste.
Cats may also prefer running water as they can find more easily by using their keen sense of hearing. Cats also have very long sensitive whiskers, so if the bowl is too narrow your cat may not like putting his/her face in as this will squash their whiskers. A wide large bowl is always best to keep their whiskers dry.